• In this strategy, reflectors, or other technologies to partially shade the sun, would be placed in space at the Lagrange point between the Earth and the Sun to reduce the amount of solar radiation absorbed by Earth. The Langrange point is a gravitationally stable point between the Earth and the Sun where their gravitational pulls cancel out. Sunshades would act to reflect or scatter sunlight in space before it reaches Earth’s atmosphere (Angel 2006). Proposals include films, dust, and mirrors, potentially using a fleet of spacecraft holding their orbits (reviewed in Baum et al. 2022). A newer proposal is for thin reflective films in the form of bubbles (Senseable City Lab 2024). The bubbles would be made of a molten material, such as silicon, and deployed as a set of rafts that would be manufactured in space.
• There have also been technologies proposed to shade Earth’s surface via Mylar reflector sheets supported by aircraft, rotors, or hydrogen balloons in the stratosphere (Komerath et al. 2017, Morrey 2023). Some of these could potentially be used to shade specific areas on Earth’s surface, such as Arctic sea ice. To date, most of the focus on sunshades has been on space deployment.

• Expected physical changes (global)
  • Reduce incoming solar radiation from space (reduces solar insolation).

• Approximately 10,000,000 km²
  • One proposal is for a 100,000 km long cloud of spacecraft (Angel 2006). Further calculations for area and distance for different scenarios provided in Angel (2006).
  • Proposal to intercept 1.7% of sunlight requires area of 20,000,000 km², a disk 800 km in radius (Govindasamy and Caldeira 2000).
    • To achieve a larger impact, a larger area is required.

• Space; many proposals focus on the Lagrange point, a gravitationally stable point between the Earth and the Sun where their gravitational pulls cancel out.

• Space

• Effecting different parts of the Earth at different times depending on Earth’s orbit, only effective during daylight and more effective during certain seasons, especially depending on latitude. Different configurations and tilt could potentially control latitudinal and seasonal variations (Sanchez and McInnes 2015).

• In this strategy, reflectors, or other technologies to partially shade the sun, would be placed in space at the Lagrange point between the Earth and the Sun to reduce the amount of solar radiation absorbed by Earth. The Langrange point is a gravitationally stable point between the Earth and the Sun where their gravitational pulls cancel out. Sunshades would act to reflect or scatter sunlight in space before it reaches Earth’s atmosphere (Angel 2006). Proposals include films, dust, and mirrors, potentially using a fleet of spacecraft holding their orbits (reviewed in Baum et al. 2022). A newer proposal is for thin reflective films in the form of bubbles (https://senseable.mit.edu/space-bubbles/). The bubbles would be made of a molten material, such as silicon, and deployed as a set of rafts that would be manufactured in space.
• There have also been technologies proposed to shade Earth’s surface via Mylar reflector sheets supported by aircraft, rotors, or hydrogen balloons in the stratosphere (Komerath et al. 2017, Morrey 2023). Some of these could potentially be used to shade specific areas on Earth’s surface, such as Arctic sea ice. To date, most of the focus on sunshades has been on space deployment.

• Expected physical changes (global)
  • Reduce incoming solar radiation from space (reduces solar insolation).

• Approximately 10,000,000 km²
  • One proposal is for a 100,000 km long cloud of spacecraft (Angel 2006). Further calculations for area and distance for different scenarios provided in Angel (2006).
  • Proposal to intercept 1.7% of sunlight requires area of 20,000,000 km², a disk 800 km in radius (Govindasamy and Caldeira 2000).
    • To achieve a larger impact, a larger area is required.

• Space; many proposals focus on the Lagrange point, a gravitationally stable point between the Earth and the Sun where their gravitational pulls cancel out.

• Space

• Effecting different parts of the Earth at different times depending on Earth’s orbit, only effective during daylight and more effective during certain seasons, especially depending on latitude. Different configurations and tilt could potentially control latitudinal and seasonal variations (Sanchez and McInnes 2015).

• In this strategy, reflectors, or other technologies to partially shade the sun, would be placed in space at the Lagrange point between the Earth and the Sun to reduce the amount of solar radiation absorbed by Earth. The Langrange point is a gravitationally stable point between the Earth and the Sun where their gravitational pulls cancel out. Sunshades would act to reflect or scatter sunlight in space before it reaches Earth’s atmosphere (Angel 2006). Proposals include films, dust, and mirrors, potentially using a fleet of spacecraft holding their orbits (reviewed in Baum et al. 2022). A newer proposal is for thin reflective films in the form of bubbles (https://senseable.mit.edu/space-bubbles/). The bubbles would be made of a molten material, such as silicon, and deployed as a set of rafts that would be manufactured in space.
• There have also been technologies proposed to shade Earth’s surface via Mylar reflector sheets supported by aircraft, rotors, or hydrogen balloons in the stratosphere (Komerath et al. 2017, Morrey 2023). Some of these could potentially be used to shade specific areas on Earth’s surface, such as Arctic sea ice. To date, most of the focus on sunshades has been on space deployment.

• Expected physical changes (global)
  • Reduce incoming solar radiation from space (reduces solar insolation).

• Approximately 10,000,000 km²
  • One proposal is for a 100,000 km long cloud of spacecraft (Angel 2006). Further calculations for area and distance for different scenarios provided in Angel (2006).
  • Proposal to intercept 1.7% of sunlight requires area of 20,000,000 km², a disk 800 km in radius (Govindasamy and Caldeira 2000).
    • To achieve a larger impact, a larger area is required.

• Space; many proposals focus on the Lagrange point, a gravitationally stable point between the Earth and the Sun where their gravitational pulls cancel out.

• Space

• Effecting different parts of the Earth at different times depending on Earth’s orbit, only effective during daylight and more effective during certain seasons, especially depending on latitude. Different configurations and tilt could potentially control latitudinal and seasonal variations (Sanchez and McInnes 2015).

• In this strategy, reflectors, or other technologies to partially shade the sun, would be placed in space at the Lagrange point between the Earth and the Sun to reduce the amount of solar radiation absorbed by Earth. The Langrange point is a gravitationally stable point between the Earth and the Sun where their gravitational pulls cancel out. Sunshades would act to reflect or scatter sunlight in space before it reaches Earth’s atmosphere (Angel 2006). Proposals include films, dust, and mirrors, potentially using a fleet of spacecraft holding their orbits (reviewed in Baum et al. 2022). A newer proposal is for thin reflective films in the form of bubbles (https://senseable.mit.edu/space-bubbles/). The bubbles would be made of a molten material, such as silicon, and deployed as a set of rafts that would be manufactured in space.
• There have also been technologies proposed to shade Earth’s surface via Mylar reflector sheets supported by aircraft, rotors, or hydrogen balloons in the stratosphere (Komerath et al. 2017, Morrey 2023). Some of these could potentially be used to shade specific areas on Earth’s surface, such as Arctic sea ice. To date, most of the focus on sunshades has been on space deployment.

• Expected physical changes (global)
  • Reduce incoming solar radiation from space (reduces solar insolation).

• Approximately 10,000,000 km²
  • One proposal is for a 100,000 km long cloud of spacecraft (Angel 2006). Further calculations for area and distance for different scenarios provided in Angel (2006).
  • Proposal to intercept 1.7% of sunlight requires area of 20,000,000 km², a disk 800 km in radius (Govindasamy and Caldeira 2000).
    • To achieve a larger impact, a larger area is required.

• Space; many proposals focus on the Lagrange point, a gravitationally stable point between the Earth and the Sun where their gravitational pulls cancel out.

• Space

• Effecting different parts of the Earth at different times depending on Earth’s orbit, only effective during daylight and more effective during certain seasons, especially depending on latitude. Different configurations and tilt could potentially control latitudinal and seasonal variations (Sanchez and McInnes 2015).

• In this strategy, reflectors, or other technologies to partially shade the sun, would be placed in space at the Lagrange point between the Earth and the Sun to reduce the amount of solar radiation absorbed by Earth. The Langrange point is a gravitationally stable point between the Earth and the Sun where their gravitational pulls cancel out. Sunshades would act to reflect or scatter sunlight in space before it reaches Earth’s atmosphere (Angel 2006). Proposals include films, dust, and mirrors, potentially using a fleet of spacecraft holding their orbits (reviewed in Baum et al. 2022). A newer proposal is for thin reflective films in the form of bubbles (https://senseable.mit.edu/space-bubbles/). The bubbles would be made of a molten material, such as silicon, and deployed as a set of rafts that would be manufactured in space.
• There have also been technologies proposed to shade Earth’s surface via Mylar reflector sheets supported by aircraft, rotors, or hydrogen balloons in the stratosphere (Komerath et al. 2017, Morrey 2023). Some of these could potentially be used to shade specific areas on Earth’s surface, such as Arctic sea ice. To date, most of the focus on sunshades has been on space deployment.

• Expected physical changes (global)
  • Reduce incoming solar radiation from space (reduces solar insolation).

• Approximately 10,000,000 km²
  • One proposal is for a 100,000 km long cloud of spacecraft (Angel 2006). Further calculations for area and distance for different scenarios provided in Angel (2006).
  • Proposal to intercept 1.7% of sunlight requires area of 20,000,000 km², a disk 800 km in radius (Govindasamy and Caldeira 2000).
    • To achieve a larger impact, a larger area is required.

• Space, many proposals focus on the Lagrange point.

• Space

• Effecting different parts of the Earth at different times depending on Earth’s orbit, only effective during daylight and more effective during certain seasons, especially depending on latitude. Different configurations and tilt could potentially control latitudinal and seasonal variations (Sanchez and McInnes 2015).

• In this strategy, reflectors, or other technologies to partially shade the sun, would be placed in space at the Lagrange point between the Earth and the Sun to reduce the amount of solar radiation absorbed by Earth. The Langrange point is a gravitationally stable point between the Earth and the Sun where their gravitational pulls cancel out. Sunshades would act to reflect or scatter sunlight in space before it reaches Earth’s atmosphere (Angel 2006). Proposals include films, dust, and mirrors, potentially using a fleet of spacecraft holding their orbits (reviewed in Baum et al. 2022). A newer proposal is for thin reflective films in the form of bubbles (https://senseable.mit.edu/space-bubbles/). The bubbles would be made of a molten material, such as silicon, and deployed as a set of rafts that would be manufactured in space.
• There have also been technologies proposed to shade Earth’s surface via Mylar reflector sheets supported by aircraft, rotors, or hydrogen balloons in the stratosphere (Komerath et al. 2017, Morrey 2023). Some of these could potentially be used to shade specific areas on Earth’s surface, such as Arctic sea ice. To date, most of the focus on sunshades has been on space deployment.

• Expected physical changes (global)
  • Reduce incoming solar radiation from space (reduces solar insolation).

• Approximately 10,000,000 km²
  • One proposal is for a 100,000 km long cloud of spacecraft (Angel 2006). Further calculations for area and distance for different scenarios provided in Angel (2006).
  • Proposal to intercept 1.7% of sunlight requires area of 20,000,000 km², a disk 800 km in radius (Govindasamy and Caldeira 2000).
    • To achieve a larger impact, a larger area is required.

• Space, many proposals focus on the Lagrange point.

• Space

• Effecting different parts of the Earth at different times depending on Earth’s orbit, only effective during daylight and more effective during certain seasons, especially depending on latitude. Different configurations and tilt could potentially control latitudinal and seasonal variations (Sanchez and McInnes 2015).

Impact on

• Unknown

• Global
  • Decrease of 1.5-6.3°C (to counteract current CO₂ levels or up to quadruple CO₂ levels).
    • Most studies have a temperature goal, generally for counteracting effects of a doubling of CO₂ concentrations (Sanchez and McInnes 2015), then discuss the space-based approach for achieving that temperature goal.
      • See Table 1 in Roy 2022, and studies reviewed in Baum et al. 2022; area of sunshade spans around 2,000,000-8,000,000 km².
      • In general, larger impacts require a larger area sunshade.
• Arctic region
  • Decreased temperature, but get undercooling in Arctic in solar dimming model simulations relative to the global temperature decrease (reviewed in Duffey et al. 2023).

• Global
  • Decrease of 2.19-8.17 W/m² (to counteract current CO₂ levels or up to quadruple CO₂ levels).
    • Most studies have a goal of decreasing a specific amount of radiative forcing or temperature, generally for counteracting effects of a doubling of CO₂ concentrations (Sanchez and McInnes 2015), and discuss what is needed to achieve that goal.
      • See Table 1 in Roy 2022, which provides areas of solar shield required for a given radiative forcing reduction to get to pre-industrial temperatures and evaluation in Lenton and Vaughan 2009; area of sunshade spans around 2,000,000-8,000,000 km².
      • In general, larger impacts require a larger area sunshade.
• Arctic region
  • Unknown

• Direct or indirect impact on sea ice?
  • Indirect via temperature change
• New or old ice?
  • Both
    • Could slow melting of existing ice and allow growth of new ice.
• Impact on sea ice
  • Increased sea ice, potential to maintain sea ice
    • Models show increased sea ice area (Govindasamy and Caldeira 2000) and provide evidence that sea ice extent could be held close to present day values (reviewed in Duffey et al. 2023). However, could require substantial amounts of solar dimming (Tilmes et al. 2014).

Scalability

• Challenging

• Unknown

• Unknown

• > 20 yr
  • Estimates range from 25 years to before end of century (Angel 2006, Ratti et al. 2022).

• > 20 yr
  • Estimates range from 25 years to before end of century (Angel 2006, Ratti et al. 2022).

Cost

• $1-$20 trillion USD
  • Studies estimate $1-$20 trillion USD for research, development, and initial deployment (Angel 2006, Kosugi 2010, Baum et al. 2022).
  • Costs could go down over time as costs of launching material in space has already decreased over time (Roy 2022).

• Unknown but likely high

Impact on

• Unknown

• Global
  • Decrease of 1.5-6.3°C (to counteract current CO₂ levels or up to quadruple CO₂ levels)
    • Most studies have a temperature goal, generally for counteracting effects of a doubling of CO₂ concentrations (Sanchez and McInnes 2015), then discuss the space-based approach for achieving that temperature goal.
      • See Table 1 in Roy 2022, and studies reviewed in Baum et al. 2022; area of sunshade spans around 2,000,000-8,000,000 km².
      • In general, larger impacts require a larger area sunshade
• Arctic region
  • Decreased temperature, but get undercooling in Arctic in solar dimming model simulations relative to the global temperature decrease (reviewed in Duffey et al. 2023)

• Global
  • Decrease of 2.19-8.17 W/m² (to counteract current CO₂ levels or up to quadruple CO₂ levels)
    • Most studies have a goal of decreasing a specific amount of radiative forcing or temperature, generally for counteracting effects of a doubling of CO₂ concentrations (Sanchez and McInnes 2015), and discuss what is needed to achieve that goal.
      • See Table 1 in Roy 2022, which provides areas of solar shield required for a given radiative forcing reduction to get to pre-industrial temperatures and evaluation in Lenton and Vaughan 2009; area of sunshade spans around 2,000,000-8,000,000 km².
      • In general, larger impacts require a larger area sunshade
• Arctic region
  • Unknown

• Direct or indirect impact on sea ice?
  • Indirect via temperature change
• New or old ice?
  • Both
    • Could slow melting of existing ice and allow growth of new ice
• Impact on sea ice
  • Increased sea ice, potential to maintain sea ice
    • Models show increased sea ice area (Govindasamy and Caldeira 2000) and provide evidence that sea ice extent could be held close to present day values (reviewed in Duffey et al. 2023). However, could require substantial amounts of solar dimming (Tilmes et al. 2014).

Scalability

• Challenging

• Unknown

• Unknown

• > 20 yr
  • Estimates range from 25 years to before end of century (Angel 2006, Ratti et al. 2022)

• > 20 yr
  • Estimates range from 25 years to before end of century (Angel 2006, Ratti et al. 2022)

Cost

• $1-$20 trillion USD
  • Studies estimate $1-$20 trillion USD for research, development, and initial deployment (Angel 2006, Kosugi 2010, Baum et al. 2022).
  • Costs could go down over time as costs of launching material in space has already decreased over time (Roy 2022)

• Unknown but likely high

Impact on

• Unknown

• Global
  • Decrease of 1.5-6.3°C (to counteract current CO₂ levels or up to quadruple CO₂ levels)
    • Most studies have a temperature goal, generally for counteracting effects of a doubling of CO₂ concentrations (Sanchez and McInnes 2015), then discuss the space-based approach for achieving that temperature goal.
      • See Table 1 in Roy 2022, and studies reviewed in Baum et al. 2022; area of sunshade spans around 2,000,000-8,000,000 km².
      • In general, larger impacts require a larger area sunshade
• Arctic region
  • Decreased temperature, but get undercooling in Arctic in solar dimming model simulations relative to the global temperature decrease (reviewed in Duffey et al. 2023)

• Global
  • Decrease of 2.19-8.17 W/m² (to counteract current CO₂ levels or up to quadruple CO₂ levels)
    • Most studies have a goal of decreasing a specific amount of radiative forcing or temperature, generally for counteracting effects of a doubling of CO₂ concentrations (Sanchez and McInnes 2015), and discuss what is needed to achieve that goal.
      • See Table 1 in Roy 2022, which provides areas of solar shield required for a given radiative forcing reduction to get to pre-industrial temperatures and evaluation in Lenton and Vaughan 2009; area of sunshade spans around 2,000,000-8,000,000 km².
      • In general, larger impacts require a larger area sunshade
• Arctic region
  • Unknown

• Direct or indirect impact on sea ice?
  • Indirect via temperature change
• New or old ice?
  • Both
    • Could slow melting of existing ice and allow growth of new ice
• Impact on sea ice
  • Increased sea ice, potential to maintain sea ice
    • Models show increased sea ice area (Govindasamy and Caldeira 2000) and provide evidence that sea ice extent could be held close to present day values (reviewed in Duffey et al. 2023). However, could require substantial amounts of solar dimming (Tilmes et al. 2014).

Scalability

• Challenging

• Unknown

• Unknown

• > 20 yr
  • Estimates range from 25 years to before end of century (Angel 2006, Ratti et al. 2022)

• > 20 yr
  • Estimates range from 25 years to before end of century (Angel 2006, Ratti et al. 2022)

Cost

• Trillions of US dollars
  • Studies estimate trillions of dollars (Angel 2006, Kosugi 2010, Baum et al. 2022).
  • Costs could go down over time as costs of launching material in space has already decreased over time (Roy 2022)

• Unknown but likely high

Impact on

• Unknown

• Global
  • Decrease of 1.5-6.3°C (to counteract current CO₂ levels or up to quadruple CO₂ levels)
    • Most studies have a temperature goal, generally for counteracting effects of a doubling of CO₂ concentrations (Sanchez and McInnes 2015), then discuss the space-based approach for achieving that temperature goal.
      • See Table 1 in Roy 2022, and studies reviewed in Baum et al. 2022; area of sunshade spans around 2,000,000-8,000,000 km².
      • In general, larger impacts require a larger area sunshade
• Arctic region
  • Decreased temperature, but get undercooling in Arctic in solar dimming model simulations relative to the global temperature decrease (reviewed in Duffey et al. 2023)

• Global
  • Decrease of 2.19-8.17 W/m² (to counteract current CO₂ levels or up to quadruple CO₂ levels)
    • Most studies have a goal of decreasing a specific amount of radiative forcing or temperature, generally for counteracting effects of a doubling of CO₂ concentrations (Sanchez and McInnes 2015), and discuss what is needed to achieve that goal.
      • See Table 1 in Roy 2022, which provides areas of solar shield required for a given radiative forcing reduction to get to pre-industrial temperatures and evaluation in Lenton and Vaughan 2009; area of sunshade spans around 2,000,000-8,000,000 km².
      • In general, larger impacts require a larger area sunshade
• Arctic region
  • Unknown

• Direct or indirect impact on sea ice?
  • Indirect via temperature change
• New or old ice?
  • Both
    • Could slow melting of existing ice and allow growth of new ice
• Impact on sea ice
  • Increased sea ice, potential to maintain sea ice
    • Models show increased sea ice area (Govindasamy and Caldeira 2000) and provide evidence that sea ice extent could be held close to present day values (reviewed in Duffey et al. 2023). However, could require substantial amounts of solar dimming (Tilmes et al. 2014).

Scalability

• Challenging

• Unknown

• Unknown

• > 20 yr
  • Estimates range from 25 years to before end of century (Angel 2006, Ratti et al. 2022)

• > 20 yr
  • Estimates range from 25 years to before end of century (Angel 2006, Ratti et al. 2022)

Cost

• Trillions of US dollars
  • Studies estimate trillions of dollars (Angel 2006, Kosugi 2010, Baum et al. 2022).
  • Costs could go down over time as costs of launching material in space has already decreased over time (Roy 2022)

• Unknown but likely high

Impact on

• Unknown

• Global
  • Decrease of 1.5-6.3°C (to counteract current CO₂ levels or up to quadruple CO₂ levels)
    • Most studies have a temperature goal, generally for counteracting effects of a doubling of CO₂ concentrations (Sanchez and McInnes 2015), then discuss the space-based approach for achieving that temperature goal.
      • See Table 1 in Roy 2022, and studies reviewed in Baum et al. 2022; area of sunshade spans around 2,000,000-8,000,000 km².
      • In general, larger impacts require a larger area sunshade
• Arctic region
  • Decreased temperature, but get undercooling in Arctic in solar dimming model simulations relative to the global temperature decrease (reviewed in Duffey et al. 2023)

• Global
  • Decrease of 2.19-8.17 W/m² (to counteract current CO₂ levels or up to quadruple CO₂ levels)
    • Most studies have a goal of decreasing a specific amount of radiative forcing or temperature, generally for counteracting effects of a doubling of CO₂ concentrations (Sanchez and McInnes 2015), and discuss what is needed to achieve that goal.
      • See Table 1 in Roy 2022, which provides areas of solar shield required for a given radiative forcing reduction to get to pre-industrial temperatures and evaluation in Lenton and Vaughan 2009; area of sunshade spans around 2,000,000-8,000,000 km².
      • In general, larger impacts require a larger area sunshade
• Arctic region
  • Unknown

• Direct or indirect impact on sea ice?
  • Indirect via temperature change
• New or old ice?
  • Both
    • Could slow melting of existing ice and allow growth of new ice
• Impact on sea ice
  • Increased sea ice, potential to maintain sea ice
    • Models show increased sea ice area (Govindasamy and Caldeira 2000) and provide evidence that sea ice extent could be held close to present day values (reviewed in Duffey et al. 2023). However, could require substantial amounts of solar dimming (Tilmes et al. 2014).

Scalability

• Challenging

• Unknown

• Unknown

• > 20 yr
  • Estimates range from 25 years to before end of century (Angel 2006, Ratti et al. 2022)

• > 20 yr
  • Estimates range from 25 years to before end of century (Angel 2006, Ratti et al. 2022)

Cost

• Trillions of US dollars
  • Studies estimate trillions of dollars (Angel 2006, Kosugi 2010, Baum et al. 2022).
  • Costs could go down over time as costs of launching material in space has already decreased over time (Roy 2022)

• Unknown but likely high

Impact on

• Unknown

• Global
  • Decrease of 1.5-6.3°C (to counteract current CO₂ levels or up to quadruple CO₂ levels)
    • Most studies have a temperature goal, generally for counteracting effects of a doubling of CO₂ concentrations (Sanchez and McInnes 2015), then discuss the space-based approach for achieving that temperature goal.
      • See Table 1 in Roy 2022, and studies reviewed in Baum et al. 2022; area of sunshade spans around 2,000,000-8,000,000 km².
      • In general, larger impacts require a larger area sunshade
• Arctic region
  • Decreased temperature, but get undercooling in Arctic in solar dimming model simulations relative to the global temperature decrease (reviewed in Duffey et al. 2023)

• Global
  • Decrease of 2.19-8.17 W/m² (to counteract current CO₂ levels or up to quadruple CO₂ levels)
    • Most studies have a goal of decreasing a specific amount of radiative forcing or temperature, generally for counteracting effects of a doubling of CO₂ concentrations (Sanchez and McInnes 2015), and discuss what is needed to achieve that goal.
      • See Table 1 in Roy 2022, which provides areas of solar shield required for a given radiative forcing reduction to get to pre-industrial temperatures and evaluation in Lenton and Vaughan 2009; area of sunshade spans around 2,000,000-8,000,000 km².
      • In general, larger impacts require a larger area sunshade
• Arctic region
  • Unknown

• Direct or indirect impact on sea ice?
  • Indirect via temperature change
• New or old ice?
  • Both
    • Could slow melting of existing ice and allow growth of new ice
• Impact on sea ice
  • Increased sea ice, potential to maintain sea ice
    • Models show increased sea ice area (Govindasamy and Caldeira 2000) and provide evidence that sea ice extent could be held close to present day values (reviewed in Duffey et al. 2023). However, could require substantial amounts of solar dimming (Tilmes et al. 2014).

Scalability

• Challenging

• Unknown

• Unknown

• > 20 yr
  • Estimates range from 25 years to before end of century (Angel 2006, Ratti et al. 2022)

• > 20 yr
  • Estimates range from 25 years to before end of century (Angel 2006, Ratti et al. 2022)

Cost

• $ Trillion
  • Studies estimate trillions of dollars (Angel 2006, Kosugi 2010, Baum et al. 2022).
  • Costs could go down over time as costs of launching material in space has already decreased over time (Roy 2022)

• Unknown but likely high

Impact on

• Global
  • No impact
• Arctic region
  • No impact

• Global
  • Decrease of 1.5-6.3°C (to counteract current CO₂ levels or up to quadruple CO₂ levels)
    • Most studies have a temperature goal, generally for counteracting effects of a doubling of CO₂ concentrations (Sanchez and McInnes 2015), then discuss the space-based approach for achieving that temperature goal.
      • See Table 1 in Roy 2022, and studies reviewed in Baum et al. 2022; area of sunshade spans around 2,000,000-8,000,000 km².
      • In general, larger impacts require a larger area sunshade
• Arctic region
  • Decreased temperature, but get undercooling in Arctic in solar dimming model simulations relative to the global temperature decrease (reviewed in Duffey et al. 2023)

• Global
  • Decrease of 2.19-8.17 W/m² (to counteract current CO₂ levels or up to quadruple CO₂ levels)
    • Most studies have a goal of decreasing a specific amount of radiative forcing or temperature, generally for counteracting effects of a doubling of CO₂ concentrations (Sanchez and McInnes 2015), and discuss what is needed to achieve that goal.
      • See Table 1 in Roy 2022, which provides areas of solar shield required for a given radiative forcing reduction to get to pre-industrial temperatures and evaluation in Lenton and Vaughan 2009; area of sunshade spans around 2,000,000-8,000,000 km².
      • In general, larger impacts require a larger area sunshade
• Arctic region
  • Unknown

• Direct or indirect impact on sea ice?
  • Indirect via temperature change
• New or old ice?
  • Both
    • Could slow melting of existing ice and allow growth of new ice
• Impact on sea ice
  • Increased sea ice, potential to maintain sea ice
    • Models show increased sea ice area (Govindasamy and Caldeira 2000) and provide evidence that sea ice extent could be held close to present day values (reviewed in Duffey et al. 2023). However, could require substantial amounts of solar dimming (Tilmes et al. 2014).

Scalability

• Challenging

• Unknown

• Unknown

• > 20 yr
  • Estimates range from 25 years to before end of century (Angel 2006, Ratti et al. 2022)

• > 20 yr
  • Estimates range from 25 years to before end of century (Angel 2006, Ratti et al. 2022)

Cost

• $ Trillion
  • Studies estimate trillions of dollars (Angel 2006, Kosugi 2010, Baum et al. 2022).
  • Costs could go down over time as costs of launching material in space has already decreased over time (Roy 2022)

• Unknown but likely high

Impact on

• Global
  • No impact
• Arctic region
  • No impact

• Global
  • Decrease of 1.5-6.3°C (to counteract current CO₂ levels or up to quadruple CO₂ levels)
    • Most studies have a temperature goal, generally for counteracting effects of a doubling of CO₂ concentrations (Sanchez and McInnes 2015), then discuss the space-based approach for achieving that temperature goal.
      • See Table 1 in Roy 2022, and studies reviewed in Baum et al. 2022; area of sunshade spans around 2,000,000-8,000,000 km².
      • In general, larger impacts require a larger area sunshade
• Arctic region
  • Decreased temperature, but get undercooling in Arctic in solar dimming model simulations relative to the global temperature decrease (reviewed in Duffey et al. 2023)

• Global
  • Decrease of 2.19-8.17 W/m² (to counteract current CO₂ levels or up to quadruple CO₂ levels)
    • Most studies have a goal of decreasing a specific amount of radiative forcing or temperature, generally for counteracting effects of a doubling of CO₂ concentrations (Sanchez and McInnes 2015), and discuss what is needed to achieve that goal.
      • See Table 1 in Roy 2022, which provides areas of solar shield required for a given radiative forcing reduction to get to pre-industrial temperatures and evaluation in Lenton and Vaughan 2009; area of sunshade spans around 2,000,000-8,000,000 km².
      • In general, larger impacts require a larger area sunshade
• Arctic region
  • Unknown

• Direct or indirect impact on sea ice?
  • Indirect via temperature change
• New or old ice?
  • Both
    • Could slow melting of existing ice and allow growth of new ice

• Increased sea ice, potential to maintain sea ice
  • Models show increased sea ice area (Govindasamy and Caldeira 2000) and provide evidence that sea ice extent could be held close to present day values (reviewed in Duffey et al. 2023). However, could require substantial amounts of solar dimming (Tilmes et al. 2014).

Scalability

• Challenging

• Unknown

• Unknown

• > 20 yr
  • Estimates range from 25 years to before end of century (Angel 2006, Ratti et al. 2022)

• > 20 yr
  • Estimates range from 25 years to before end of century (Angel 2006, Ratti et al. 2022)

Cost

• $ Trillion
  • Studies estimate trillions of dollars (Angel 2006, Kosugi 2010, Baum et al. 2022).
  • Costs could go down over time as costs of launching material in space has already decreased over time (Roy 2022)

• Unknown but likely high

Impact on

• Global
  • No impact
• Arctic region
  • No impact

• Global
  • Decrease of 1.5-6.3°C (to counteract current CO₂ levels or up to quadruple CO₂ levels)
    • Most studies have a temperature goal, generally for counteracting effects of a doubling of CO₂ concentrations (Sanchez and McInnes 2015), then discuss the space-based approach for achieving that temperature goal.
      • See Table 1 in Roy 2022, and studies reviewed in Baum et al. 2022; area of sunshade spans around 2,000,000-8,000,000 km².
      • In general, larger impacts require a larger area sunshade
    • Arctic region
      • Decreased temperature, but get undercooling in Arctic in solar dimming model simulations relative to the global temperature decrease (reviewed in Duffey et al. 2023)

• Global
  • Decrease of 2.19-8.17 W/m² (to counteract current CO₂ levels or up to quadruple CO₂ levels)
    • Most studies have a goal of decreasing a specific amount of radiative forcing or temperature, generally for counteracting effects of a doubling of CO₂ concentrations (Sanchez and McInnes 2015), and discuss what is needed to achieve that goal.
      • See Table 1 in Roy 2022, which provides areas of solar shield required for a given radiative forcing reduction to get to pre-industrial temperatures and evaluation in Lenton and Vaughan 2009; area of sunshade spans around 2,000,000-8,000,000 km².
      • In general, larger impacts require a larger area sunshade
    • Arctic region
      • Unknown

• Direct or indirect impact on sea ice?
  • Indirect via temperature change
• New or old ice?
  • Both
    • Could slow melting of existing ice and allow growth of new ice

• Increased sea ice, potential to maintain sea ice
  • Models show increased sea ice area (Govindasamy and Caldeira 2000) and provide evidence that sea ice extent could be held close to present day values (reviewed in Duffey et al. 2023). However, could require substantial amounts of solar dimming (Tilmes et al. 2014).

Scalability

• Challenging

• Unknown

• Unknown

• > 20 yr
  • Estimates range from 25 years to before end of century (Angel 2006, Ratti et al. 2022)

• > 20 yr
  • Estimates range from 25 years to before end of century (Angel 2006, Ratti et al. 2022)

Cost

• $ Trillion
  • Studies estimate trillions of dollars (Angel 2006, Kosugi 2010, Baum et al. 2022).
  • Costs could go down over time as costs of launching material in space has already decreased over time (Roy 2022)

• Unknown but likely high

• 3 – Conceptual, modeling, and feasibility studies.
• Summary of existing literature and studies:
  • Conceptual studies and technology plans (Angel 2006, Maheswaran et al. 2023), feasibility study (Roy 2022)
  • Modeling studies (reviewed in Irvine et al. 2016 and Baum et al. 2022)
    • Most modeling studies use the Geoengineering Model Intercomparison Project (GeoMIP) with idealized sunshade geoengineering experiment G1 that reduces solar insolation by a certain percentage depending on scenario (Irvine et al. 2016).
  • Laboratory studies at the Massachusetts Institute of Technology (MIT) tested bubbles in experimental setting mimicking conditions of outer space.
  • If deployed via fleet of spacecraft, some of the technologies required for solar shield elements have been demonstrated, with more studies planned in the coming years (Roy 2022).

• Not feasible

• • 3 – Conceptual, modeling, and feasibility studies.
  • Summary of existing literature and studies:
    • Conceptual studies and technology plans (Angel 2006, Maheswaran et al. 2023), feasibility study (Roy 2022)
    • Modeling studies (reviewed in Irvine et al. 2016 and Baum et al. 2022)
      • Most modeling studies use the Geoengineering Model Intercomparison Project (GeoMIP) with idealized sunshade geoengineering experiment G1 that reduces solar insolation by a certain percentage depending on scenario (Irvine et al. 2016).
    • Laboratory studies at the Massachusetts Institute of Technology (MIT) tested bubbles in experimental setting mimicking conditions of outer space.
    • If deployed via fleet of spacecraft, some of the technologies required for solar shield elements have been demonstrated, with more studies planned in the coming years (Roy 2022).

• • Not feasible

• • 3 – Conceptual, modeling, and feasibility studies.
  • Summary of existing literature and studies:
    • Conceptual studies and technology plans (Angel 2006, Maheswaran et al. 2023), feasibility study (Roy 2022)
    • Modeling studies (reviewed in Irvine et al. 2016 and Baum et al. 2022)
      • Most modeling studies use the Geoengineering Model Intercomparison Project (GeoMIP) with idealized sunshade geoengineering experiment G1 that reduces solar insolation by a certain percentage depending on scenario. (Irvine et al. 2016)
    • Laboratory studies at the Massachusetts Institute of Technology (MIT) tested bubbles in experimental setting mimicking conditions of outer space
    • If deployed via fleet of spacecraft, some of the technologies required for solar shield elements have been demonstrated, with more studies planned in the coming years (Roy 2022)

• • Not feasible

• TRL
  • 3 – Conceptual, modeling, and feasibility studies.
  • Summary of existing literature and studies:
    • Conceptual studies and technology plans (Angel 2006, Maheswaran et al. 2023), feasibility study (Roy 2022)
    • Modeling studies (reviewed in Irvine et al. 2016 and Baum et al. 2022)
      • Most modeling studies use the Geoengineering Model Intercomparison Project (GeoMIP) with idealized sunshade geoengineering experiment G1 that reduces solar insolation by a certain percentage depending on scenario. (Irvine et al. 2016)
    • Laboratory studies at the Massachusetts Institute of Technology (MIT) tested bubbles in experimental setting mimicking conditions of outer space
    • If deployed via fleet of spacecraft, some of the technologies required for solar shield elements have been demonstrated, with more studies planned in the coming years (Roy 2022)
• Technical feasibility within 10 yrs
  • Not feasible

Physical and chemical changes

• Co-benefits
  • Compared to some other interventions, space shading does not impact the composition of the atmosphere or ocean (Angel 2006).
  • Less impact on hydrological cycle / precipitation than SAI (reviewed in Irvine et al. 2016).
• Risks
  • Increased stratospheric cooling which could decrease stratospheric ozone (Govindasamy and Caldeira 2000).
  • Some impact on hydrological cycle / precipitation possible, but less than with SAI (reviewed in Irvine et al. 2016).
  • Launching a fleet of spacecraft will release water vapor, a greenhouse gas, which may be retained in the stratosphere (Roy 2022).
  • During reentry of launching devices nitrous oxide is generated in the stratosphere which may deplete ozone (Roy 2022).
  • Risk of space debris and subsequent collisions.

Impacts on species

• Co-benefits
  • Unknown
• Risks
  • Unknown

Impacts on ecosystems

• Co-benefits
  • Unlike SAI, would not directly impact biosphere (Baum et al. 2022).
• Risks
  • Unknown

Impacts on society

• Co-benefits
  • Advances in knowledge and technologies related to space.
  • Researchers are exploring the possibility for generating power in space that is transmitted back to Earth, and such a system could be deployed on the space shields or be used to power a laser array (Roy 2022). The amount of power generated could fulfill energy production needs on Earth (Baum et al. 2022).
• Risks
  • Risk of non-functional spacecraft colliding with Earth-orbiting spacecraft (Angel 2006), this would depend on what type of sunshade is used and how deployed.

Ease of reversibility

• Medium
  • Seen as more reversible than SAI (Baum et al. 2022).
  • For sunshades, if needed to be terminated the device could be released into deep space (Baum et al. 2022).
  • Space bubbles could be intentionally destroyed with minimal debris (Ratti et al. 2022).

Risk of termination shock

• High
  • The lifetime of a fleet of stationary spacecraft is estimated to be about 50 years (Angel 2006). Once the spacecraft were no longer operational the sunshade effect would be gone, and the Earth would warm. Phaseout approaches could be designed to avoid termination shock (Ratti et al. 2022).

Physical and chemical changes

• Co-benefits
  • Compared to some other interventions, space shading does not impact the composition of the atmosphere or ocean (Angel 2006).
  • Less impact on hydrological cycle / precipitation than SAI (reviewed in Irvine et al. 2016).
• Risks
  • Increased stratospheric cooling which could decrease stratospheric ozone (Govindasamy and Caldeira 2000).
  • Some impact on hydrological cycle / precipitation possible, but less than with SAI (reviewed in Irvine et al. 2016).
  • Launching a fleet of spacecraft will release water vapor, a greenhouse gas, which may be retained in the stratosphere (Roy 2022).
  • During reentry of launching devices nitrous oxide is generated in the stratosphere which may deplete ozone (Roy 2022).
  • Risk of space debris and subsequent collisions.

Impacts on species

• Co-benefits
  • Unknown
• Risks
  • Unknown

Impacts on ecosystems

• Co-benefits
  • Unlike SAI, would not directly impact biosphere (Baum et al. 2022).
• Risks
  • Unknown

Impacts on society

• Co-benefits
  • Advances in knowledge and technologies related to space.
  • Researchers are exploring the possibility for generating power in space that is transmitted back to Earth, and such a system could be deployed on the space shields or be used to power a laser array (Roy 2022). The amount of power generated could fulfill energy production needs on Earth (Baum et al. 2022).
• Risks
  • Risk of non-functional spacecraft colliding with Earth-orbiting spacecraft (Angel 2006), this would depend on what type of sunshade is used and how deployed.

Ease of reversibility

• Seen as more reversible than SAI (Baum et al. 2022).
• For sunshades, if needed to be terminated the device could be released into deep space (Baum et al. 2022).
• Space bubbles could be intentionally destroyed with minimal debris (Ratti et al. 2022).

Risk of termination shock

• The lifetime of a fleet of stationary spacecraft is estimated to be about 50 years (Angel 2006). Once the spacecraft were no longer operational the sunshade effect would be gone, and the Earth would warm. Phaseout approaches could be designed to avoid termination shock (Ratti et al. 2022).

• Co-benefits
  • Compared to some other interventions, space shading does not impact the composition of the atmosphere or ocean (Angel 2006).
  • Less impact on hydrological cycle / precipitation than SAI (reviewed in Irvine et al. 2016).
• Risks
  • Increased stratospheric cooling which could decrease stratospheric ozone (Govindasamy and Caldeira 2000).
  • Some impact on hydrological cycle / precipitation possible, but less than with SAI (reviewed in Irvine et al. 2016).
  • Launching a fleet of spacecraft will release water vapor, a greenhouse gas, which may be retained in the stratosphere (Roy 2022).
  • During reentry of launching devices nitrous oxide is generated in the stratosphere which may deplete ozone (Roy 2022).
  • Risk of space debris and subsequent collisions.

• Co-benefits
  • Unknown
• Risks
  • Unknown

• Co-benefits
  • Unlike SAI, would not directly impact biosphere (Baum et al. 2022).
• Risks
  • Unknown

• Co-benefits
  • Advances in knowledge and technologies related to space.
  • Researchers are exploring the possibility for generating power in space that is transmitted back to Earth, and such a system could be deployed on the space shields or be used to power a laser array (Roy 2022). The amount of power generated could fulfill energy production needs on Earth (Baum et al. 2022).
• Risks
  • Risk of non-functional spacecraft colliding with Earth-orbiting spacecraft (Angel 2006), this would depend on what type of sunshade is used and how deployed.

• Seen as more reversible than SAI (Baum et al. 2022).
• For sunshades, if needed to be terminated the device could be released into deep space (Baum et al. 2022).
• Space bubbles could be intentionally destroyed with minimal debris (Ratti et al. 2022).

• The lifetime of a fleet of stationary spacecraft is estimated to be about 50 years (Angel 2006). Once the spacecraft were no longer operational the sunshade effect would be gone, and the Earth would warm. Phaseout approaches could be designed to avoid termination shock (Ratti et al. 2022).

• Co-benefits
  • Compared to some other interventions, space shading does not impact the composition of the atmosphere or ocean (Angel 2006)
  • Less impact on hydrological cycle / precipitation than SAI (reviewed in Irvine et al. 2016)
• Risks
  • Increased stratospheric cooling which could decrease stratospheric ozone (Govindasamy and Caldeira 2000)
  • Some impact on hydrological cycle / precipitation possible, but less than with SAI (reviewed in Irvine et al. 2016)
  • Launching a fleet of spacecraft will release water vapor, a greenhouse gas, which may be retained in the stratosphere (Roy 2022)
  • During reentry of launching devices nitrous oxide is generated in the stratosphere which may deplete ozone (Roy 2022)
  • Risk of space debris and subsequent collisions

• Co-benefits
  • Unknown
• Risks
  • Unknown

• Co-benefits
  • Unlike SAI, would not directly impact biosphere (Baum et al. 2022)
• Risks
  • Unknown

• Co-benefits
  • Advances in knowledge and technologies related to space
  • Researchers are exploring the possibility for generating power in space that is transmitted back to Earth, and such a system could be deployed on the space shields or be used to power a laser array (Roy 2022). The amount of power generated could fulfill energy production needs on Earth (Baum et al. 2022).
• Risks
  • Risk of non-functional spacecraft colliding with Earth-orbiting spacecraft (Angel 2006), this would depend on what type of sunshade is used and how deployed

• Seen as more reversible than SAI (Baum et al. 2022).
• For sunshades, if needed to be terminated the device could be released into deep space (Baum et al. 2022).
• Space bubbles could be intentionally destroyed with minimal debris (Ratti et al. 2022).

• The lifetime of a fleet of stationary spacecraft is estimated to be about 50 years (Angel 2006). Once the spacecraft were no longer operational the sunshade effect would be gone, and the Earth would warm. Phaseout approaches could be designed to avoid termination shock (Ratti et al. 2022).

• Applicable to all approaches within Solar Radiation Modification:
  • International regulations would likely need to be considered for all Solar Radiation Modification approaches as transboundary effects are likely, especially for larger field experiments and deployment, dependent on scale and area of application. Some research activities may fall under national jurisdiction.
• Specific to Sunshades:
  • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There is no formal governance framework for this approach (UNEP 2023). Governance efforts to date have been scattered and ad hoc (NASEM 2021). Governance is needed for at least two different levels: research and deployment (DSG).
    • The National Academy of Sciences’ (2021) report “Reflecting Sunlight: Recommendations for solar geoengineering research and research governance landscape” provides an overview of laws and international treaties that might apply to SRM. These include:
      • Domestic Law
        • US National Environmental Policy Act and state analogs
        • US Weather Modification Reporting Act and state analogs
        • Regulatory statutes
        • Tort Liability
        • Intellectual property law
      • International Environmental Law
        • Treaty Law
          • UN Convention on Biological Diversity
          • London Convention/London Protocol
          • UN Framework Convention on Climate Change
          • Vienna Convention and Montreal Protocol
          • Convention on Long-Range Transboundary Air Pollution (CLRTAP)
          • Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques (ENMOD)
          • UN Convention on the Law of the Sea
        • Customary International Law and Principles
          • Prevention of transboundary harm principle
          • Principle of intergenerational equity
          • The precautionary principle
          • Sustainable development goals
  • It will be important to distinguish small-scale perturbation experiments without climate relevance versus larger-scale testing that may be indistinguishable from deployment.
  • NASEM (2021) provides a proposed framework and approach for SRM research and governance, which emphasis engagement, input, and assessment. This includes exit ramps – “criteria and protocols for terminating research programs or areas” (NASEM 2021).
  • A report by the Climate Overshoot Commission (2023) calls for research on SRM and governance discussions as well as moratorium on SRM deployment and large-scale outdoor experiments.
  • UNESCO World Commission on the Ethics of Scientific Knowledge and Technology’s (COMEST) 2023 Report on the ethics of climate engineering has a slate of recommendations related to SRM covering governance, participation and inclusion, role of scientific knowledge and research strengthening capacity, and education, awareness, and advocacy.
  • In the absence of a governance framework there have been calls for governments to prohibit the development and deployment of SRM (Gupta et al. 2024). There is a need for governments to discuss coordination of research governance (Jinnah et al. 2024b).
  • An independent advisory committee for Harvard University’s Stratospheric Controlled Perturbation Experiment (SCoPEX) applied a research governance framework to the SCoPEx proposal detailed in the advisory committee’s final report (Jinnah et al. 2024a), which may inform future governance of outdoor experiments; this framework could potentially be applied to other atmospheric SRM approaches.
• Specific to Sunshades:
  • There is currently no legal prohibition for climate intervention projects in space (Bodansky 1996). There are some frameworks that provide some guidance for space activities, but they are likely insufficient (Baum et al. 2022). These include:
  • The Outer Space Treaty of 1967 establishes outer space as “the province of all mankind” and establishes open access; any state is free to use space (Bodansky 1996, Baum et al. 2022)
    • Under this treaty, “the exploration and use of outer space … shall be carried out for the benefit and in the interests of all countries, irrespective of their degree of economic or scientific development”.
    • States are to avoid “adverse changes in the environment of the Earth” and are expected to consult with other states about whether an activity might have adverse effects (Bodansky 1996). However, there are no mechanisms for decision-making or resolving disputes (Bodansky 1996).
  • The UN Commission on Peaceful Uses of Outer Space, established by the UN General Assembly in 1959, aims for benefits of space technologies to apply to all countries (Baum et al. 2022).
  • The Environmental Modification Convention is a 1978 UN treaty that “prohibits military or hostile use of environmental modification techniques with widespread, long-lasting, or severe effects” (Baum et al. 2022).
  • See Goguichvili et al. (2021) for an overview on space governance (not specific to climate intervention).

• See DSG (2023), A justice-based analysis of solar geoengineering and capacity building
• Here we define justice related to approaches to slow the loss of Arctic sea ice through distributive justice, procedural justice, and restorative justice. Following COMEST (2023), we consider questions of ethics through a justice lens. Note that this is not an exhaustive list of justice dimensions and as the field advances, so will the related considerations and dimensions.
• General comment on justice: “A well-designed mission-driven research program that aims to evaluate solar geoengineering could promote justice and legitimacy, among other valuable ends. Specifically, an international, mission-driven research program that aims to produce knowledge to enable well-informed decision-making about solar geoengineering could (1) provide a more effective way to identify and answer the questions that policymakers would need to answer; and (2) provide a venue for more efficient, effective, just, and legitimate governance of solar geoengineering research; while (3) reducing the tendency for solar geoengineering research to exacerbate international domination” (Morrow 2019).
• Distributive justice
  • Applicable to all approaches within Solar Radiation Modification:
    • Impacts from solar geoengineering have potential to cause disproportionate harm to those least responsible for climate change (DSG 2023). It is also possible that communities most exposed or vulnerable to climate hazards receive the most benefit, depending on the deployment. There is concern from vulnerable populations that research will overlook local needs and worsen global inequities (C2G 2021 Evidence Brief). There is an urgent need for justice-based recommendations (DSG 2023).
  • Specific to Sunshades:
    • Climate intervention in space would have global effects. Recent statements by United States officials claim that space is not a global commons or public good (Sutch and Roberts 2019). The assertion of individual states to rights to space and a race for dominion exacerbates unequal power relations and threatens distributive justice (Sutch and Roberts 2019). Hobe (2007) states that ideas of distributive justice included in Outer Space Treaty are not in practice. Claims about common interest in humanity and environment could be used in international law to reassert commons values in space and to challenge unilateralism (Sutch and Roberts 2019). Deplano (2023) proposes adoption of a proportionality test to guide benefit sharing under the Outer Space Treaty.
• Procedural justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If procedural justice is considered, people affected by research would have an opportunity to participate and have a say in how the approach will be researched, deployed, and governed. Because these approaches have global ramifications, procedural justice will be challenging (Preston 2013).
    • Efforts to support procedural justice for SRM in general to date have been inadequate (DSG 2023). Because of uncertainty in outcomes, variable interests, and the potential for wide-ranging effects, procedural justice is critical (DSG 2023).
    • Diversity within the SRM research community has generally been lacking (NASEM 2021). To address this, some organizations have supported participation in research for the Global South, but there has been a lack of attention on support for participation in governance (DSG 2023). Therefore, organizations and people may understand the science of an approach but not know how to translate their interests around the issue into policy, which is a significant justice gap (DSG 2023).
    • Bennett et al. (2022) suggests an inclusive governance approach that incorporates stakeholder concerns in the design and deployment of approaches and effectively communicates risk. Within the development of such a framework there is an opportunity to prioritize procedural justice (Morrow 2019) and Indigenous self-determination (Chuffart et al. 2023). Note, however, that stakeholders may also include non-local people.
  • Specific to Sunshades:
    • No additional information
• Restorative justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If restorative justice is considered, plans would be developed for those who could be harmed by the approach to be compensated, rehabilitated, or restored (Preston 2013).
    • Horton and Keith (2019) proposed an international climate risk insurance pool where states supporting SRM deployment support the pool and opposing states would be insured against SRM risks.
  • Specific to Sunshades:
    • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There have been a series of open letters from academics and others that reject (Call for Non-Use Agreement) or support (Importance of Research on SRM, Call for Balance) solar radiation modification research, showing the current varying opinions that are shaping public perception.
  • The SCoPEx independent advisory committee offered four core principles for societal engagement related to solar radiation modification:
    • Start engagement efforts as early as possible.
    • Include social scientists with engagement expertise on research teams during the research design process.
    • Don’t presuppose what communities will be concerned about.
    • Develop a plan to be responsive to community concern.
  • A recent study on public perceptions found that people surveyed in the Global South were generally more supportive of research and development into SRM technologies compared to those from the Global North (Baum et al. 2024). Those from the Global South also expressed concern about unequal distribution of risks between rich and poor countries (Baum et al. 2024).
• Specific to Sunshades:
  • The public has not really been engaged in this topic (Baum et al. 2022).
  • No assessments of public perception, but one study conducted interviews with experts (Baum et al. 2022).
    • Among experts interviewed by Baum et al. (2022), space-based proposals have several advantages compared to other SRM techniques, such as:
      • not directly interfering with Earth’s biosphere
      • not needing to be redeployed every year (more likely every few decades)
    • The main concerns from experts interviewed by (Baum et al. 2022) included:
      • Concern that space geoengineering is too speculative, therefore resources would be better spent on other activities.
      • The moral hazard argument, as space-based techniques do not address the cause of climate change.
      • Concern that space-based methods won’t be ready for deployment when they would be needed.

• Applicable to all approaches within Solar Radiation Modification:
  • The principle of free, prior, and informed consent (FPIC) in the United Nations Declaration on the Rights of Indigenous Peoples (UNDRIP) is the foundation for engagement with Indigenous Peoples.
  • Particular to any potential Arctic research or deployment, The Inuit Circumpolar Council (2022) has published Circumpolar Inuit Protocols for Equitable and Ethical Engagement, which include eight protocols:
    • ‘Nothing About Us Without Us’ – Always Engage with Inuit
    • Recognize Indigenous Knowledge in its Own Right
    • Practice Good Governance
    • Communication with Intent
    • Exercising Accountability – Building Trust
    • Building Meaningful Partnerships
    • Information, Data Sharing, Ownership, and Permissions
    • Equitably Fund Inuit Representation and Knowledge
  • Any meaningful engagement with Indigenous peoples needs to consider context. Whyte (2018) states, “Indigenous voices should be involved in scientific and policy discussions of different types of geoengineering. But, context matters. Geoengineering discourses cannot just be associated with geoengineering to the exclusion of topics and solutions that Indigenous peoples value.”
• Specific to Sunshades:
  • Unknown
    • It is likely that Indigenous communities have not been engaged in this topic. Article 25 of the UN Declaration on the Rights of Indigenous Peoples (UNDRIP) protects Indigenous lands, specifically those traditionally occupied or used by Indigenous peoples, and does not directly protect any spiritual relationship of Indigenous peoples with outer space (Finnegan 2022). Finnegan (2022) calls for inclusion of Indigenous voices into conversations around international space plans and proposes several avenues.

• Applicable to all approaches within Solar Radiation Modification:
  • International regulations would likely need to be considered for all Solar Radiation Modification approaches as transboundary effects are likely, especially for larger field experiments and deployment, dependent on scale and area of application. Some research activities may fall under national jurisdiction.
• Specific to Sunshades:
  • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There is no formal governance framework for this approach (UNEP 2023). Governance efforts to date have been scattered and ad hoc (NASEM 2021). Governance is needed for at least two different levels: research and deployment (DSG).
    • The National Academy of Sciences’ (2021) report “Reflecting Sunlight: Recommendations for solar geoengineering research and research governance landscape” provides an overview of laws and international treaties that might apply to SRM. These include:
      • Domestic Law
        • US National Environmental Policy Act and state analogs
        • US Weather Modification Reporting Act and state analogs
        • Regulatory statutes
        • Tort Liability
        • Intellectual property law
      • International Environmental Law
        • Treaty Law
          • UN Convention on Biological Diversity
          • London Convention/London Protocol
          • UN Framework Convention on Climate Change
          • Vienna Convention and Montreal Protocol
          • Convention on Long-Range Transboundary Air Pollution (CLRTAP)
          • Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques (ENMOD)
          • UN Convention on the Law of the Sea
        • Customary International Law and Principles
          • Prevention of transboundary harm principle
          • Principle of intergenerational equity
          • The precautionary principle
          • Sustainable development goals
  • It will be important to distinguish small-scale perturbation experiments without climate relevance versus larger-scale testing that may be indistinguishable from deployment.
  • NASEM (2021) provides a proposed framework and approach for SRM research and governance, which emphasis engagement, input, and assessment. This includes exit ramps – “criteria and protocols for terminating research programs or areas” (NASEM 2021).
  • A report by the Climate Overshoot Commission (2023) calls for research on SRM and governance discussions as well as moratorium on SRM deployment and large-scale outdoor experiments.
  • UNESCO World Commission on the Ethics of Scientific Knowledge and Technology’s (COMEST) 2023 Report on the ethics of climate engineering has a slate of recommendations related to SRM covering governance, participation and inclusion, role of scientific knowledge and research strengthening capacity, and education, awareness, and advocacy.
  • In the absence of a governance framework there have been calls for governments to prohibit the development and deployment of SRM (Gupta et al. 2024). There is a need for governments to discuss coordination of research governance (Jinnah et al. 2024b).
  • An independent advisory committee for Harvard University’s Stratospheric Controlled Perturbation Experiment (SCoPEX) applied a research governance framework to the SCoPEx proposal detailed in the advisory committee’s final report (Jinnah et al. 2024a), which may inform future governance of outdoor experiments; this framework could potentially be applied to other atmospheric SRM approaches.
• Specific to Sunshades:
  • There is currently no legal prohibition for climate intervention projects in space (Bodansky 1996). There are some frameworks that provide some guidance for space activities, but they are likely insufficient (Baum et al. 2022). These include:
  • The Outer Space Treaty of 1967 establishes outer space as “the province of all mankind” and establishes open access; any state is free to use space (Bodansky 1996, Baum et al. 2022)
    • Under this treaty, “the exploration and use of outer space … shall be carried out for the benefit and in the interests of all countries, irrespective of their degree of economic or scientific development”.
    • States are to avoid “adverse changes in the environment of the Earth” and are expected to consult with other states about whether an activity might have adverse effects (Bodansky 1996). However, there are no mechanisms for decision-making or resolving disputes (Bodansky 1996).
  • The UN Commission on Peaceful Uses of Outer Space, established by the UN General Assembly in 1959, aims for benefits of space technologies to apply to all countries (Baum et al. 2022).
  • The Environmental Modification Convention is a 1978 UN treaty that “prohibits military or hostile use of environmental modification techniques with widespread, long-lasting, or severe effects” (Baum et al. 2022).
  • See Goguichvili et al. (2021) for an overview on space governance (not specific to climate intervention).

• See DSG (2023), A justice-based analysis of solar geoengineering and capacity building
• Here we define justice related to approaches to slow the loss of Arctic sea ice through distributive justice, procedural justice, and restorative justice. Following COMEST (2023), we consider questions of ethics through a justice lens. Note that this is not an exhaustive list of justice dimensions and as the field advances, so will the related considerations and dimensions.
• Distributive justice
  • Applicable to all approaches within Solar Radiation Modification:
    • Impacts from solar geoengineering have potential to cause disproportionate harm to those least responsible for climate change (DSG 2023). It is also possible that communities most exposed or vulnerable to climate hazards receive the most benefit, depending on the deployment. There is concern from vulnerable populations that research will overlook local needs and worsen global inequities (C2G 2021 Evidence Brief). There is an urgent need for justice-based recommendations (DSG 2023).
  • Specific to Sunshades:
    • Climate intervention in space would have global effects. Recent statements by United States officials claim that space is not a global commons or public good (Sutch and Roberts 2019). The assertion of individual states to rights to space and a race for dominion exacerbates unequal power relations and threatens distributive justice (Sutch and Roberts 2019). Hobe (2007) states that ideas of distributive justice included in Outer Space Treaty are not in practice. Claims about common interest in humanity and environment could be used in international law to reassert commons values in space and to challenge unilateralism (Sutch and Roberts 2019). Deplano (2023) proposes adoption of a proportionality test to guide benefit sharing under the Outer Space Treaty.
• Procedural justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If procedural justice is considered, people affected by research would have an opportunity to participate and have a say in how the approach will be researched, deployed, and governed. Because these approaches have global ramifications, procedural justice will be challenging (Preston 2013).
    • Efforts to support procedural justice for SRM in general to date have been inadequate (DSG 2023). Because of uncertainty in outcomes, variable interests, and the potential for wide-ranging effects, procedural justice is critical (DSG 2023).
    • Diversity within the SRM research community has generally been lacking (NASEM 2021). To address this, some organizations have supported participation in research for the Global South, but there has been a lack of attention on support for participation in governance (DSG 2023). Therefore, organizations and people may understand the science of an approach but not know how to translate their interests around the issue into policy, which is a significant justice gap (DSG 2023).
    • Bennett et al. (2022) suggests an inclusive governance approach that incorporates stakeholder concerns in the design and deployment of approaches and effectively communicates risk. Within the development of such a framework there is an opportunity to prioritize procedural justice (Morrow 2019) and Indigenous self-determination (Chuffart et al. 2023). Note, however, that stakeholders may also include non-local people.
  • Specific to Sunshades:
    • No additional information
• Restorative justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If restorative justice is considered, plans would be developed for those who could be harmed by the approach to be compensated, rehabilitated, or restored (Preston 2013).
    • Horton and Keith (2019) proposed an international climate risk insurance pool where states supporting SRM deployment support the pool and opposing states would be insured against SRM risks.
  • Specific to Sunshades:
    • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There have been a series of open letters from academics and others that reject (Call for Non-Use Agreement) or support (Importance of Research on SRM, Call for Balance) solar radiation modification research, showing the current varying opinions that are shaping public perception.
  • The SCoPEx independent advisory committee offered four core principles for societal engagement related to solar radiation modification:
    • Start engagement efforts as early as possible.
    • Include social scientists with engagement expertise on research teams during the research design process.
    • Don’t presuppose what communities will be concerned about.
    • Develop a plan to be responsive to community concern.
  • A recent study on public perceptions found that people surveyed in the Global South were generally more supportive of research and development into SRM technologies compared to those from the Global North (Baum et al. 2024). Those from the Global South also expressed concern about unequal distribution of risks between rich and poor countries (Baum et al. 2024).
• Specific to Sunshades:
  • The public has not really been engaged in this topic (Baum et al. 2022).
  • No assessments of public perception, but one study conducted interviews with experts (Baum et al. 2022).
    • Among experts interviewed by Baum et al. (2022), space-based proposals have several advantages compared to other SRM techniques, such as:
      • not directly interfering with Earth’s biosphere
      • not needing to be redeployed every year (more likely every few decades)
    • The main concerns from experts interviewed by (Baum et al. 2022) included:
      • Concern that space geoengineering is too speculative, therefore resources would be better spent on other activities.
      • The moral hazard argument, as space-based techniques do not address the cause of climate change.
      • Concern that space-based methods won’t be ready for deployment when they would be needed.

• Applicable to all approaches within Solar Radiation Modification:
  • The principle of free, prior, and informed consent (FPIC) in the United Nations Declaration on the Rights of Indigenous Peoples (UNDRIP) is the foundation for engagement with Indigenous Peoples.
  • Particular to any potential Arctic research or deployment, The Inuit Circumpolar Council (2022) has published Circumpolar Inuit Protocols for Equitable and Ethical Engagement, which include eight protocols:
    • ‘Nothing About Us Without Us’ – Always Engage with Inuit
    • Recognize Indigenous Knowledge in its Own Right
    • Practice Good Governance
    • Communication with Intent
    • Exercising Accountability – Building Trust
    • Building Meaningful Partnerships
    • Information, Data Sharing, Ownership, and Permissions
    • Equitably Fund Inuit Representation and Knowledge
  • Any meaningful engagement with Indigenous peoples needs to consider context. Whyte (2018) states, “Indigenous voices should be involved in scientific and policy discussions of different types of geoengineering. But, context matters. Geoengineering discourses cannot just be associated with geoengineering to the exclusion of topics and solutions that Indigenous peoples value.”
• Specific to Sunshades:
  • Unknown
    • It is likely that Indigenous communities have not been engaged in this topic. Article 25 of the UN Declaration on the Rights of Indigenous Peoples (UNDRIP) protects Indigenous lands, specifically those traditionally occupied or used by Indigenous peoples, and does not directly protect any spiritual relationship of Indigenous peoples with outer space (Finnegan 2022). Finnegan (2022) calls for inclusion of Indigenous voices into conversations around international space plans and proposes several avenues.

• Applicable to all approaches within Solar Radiation Modification:
  • International regulations would likely need to be considered for all Solar Radiation Modification approaches as transboundary effects are likely, especially for larger field experiments and deployment, dependent on scale and area of application. Some research activities may fall under national jurisdiction.
• Specific to Sunshades:
  • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There is no formal governance framework for this approach (UNEP 2023). Governance efforts to date have been scattered and ad hoc (NASEM 2021). Governance is needed for at least two different levels: research and deployment (DSG).
    • The National Academy of Sciences’ (2021) report “Reflecting Sunlight: Recommendations for solar geoengineering research and research governance landscape” provides an overview of laws and international treaties that might apply to SRM. These include:
      • Domestic Law
        • US National Environmental Policy Act and state analogs
        • US Weather Modification Reporting Act and state analogs
        • Regulatory statutes
        • Tort Liability
        • Intellectual property law
      • International Environmental Law
        • Treaty Law
          • UN Convention on Biological Diversity
          • London Convention/London Protocol
          • UN Framework Convention on Climate Change
          • Vienna Convention and Montreal Protocol
          • Convention on Long-Range Transboundary Air Pollution (CLRTAP)
          • Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques (ENMOD)
          • UN Convention on the Law of the Sea
        • Customary International Law and Principles
          • Prevention of transboundary harm principle
          • Principle of intergenerational equity
          • The precautionary principle
          • Sustainable development goals
        • It will be important to distinguish small-scale perturbation experiments without climate relevance versus larger-scale testing that may be indistinguishable from deployment.
        • NASEM (2021) provides a proposed framework and approach for SRM research and governance, which emphasis engagement, input, and assessment. This includes exit ramps – “criteria and protocols for terminating research programs or areas” (NASEM 2021).
        • A report by the Climate Overshoot Commission (2023) calls for research on SRM and governance discussions as well as moratorium on SRM deployment and large-scale outdoor experiments.
        • UNESCO World Commission on the Ethics of Scientific Knowledge and Technology’s (COMEST) 2023 Report on the ethics of climate engineering has a slate of recommendations related to SRM covering governance, participation and inclusion, role of scientific knowledge and research strengthening capacity, and education, awareness, and advocacy.
        • In the absence of a governance framework there have been calls for governments to prohibit the development and deployment of SRM (Gupta et al. 2024). There is a need for governments to discuss coordination of research governance (Jinnah et al. 2024b).
        • An independent advisory committee for Harvard University’s Stratospheric Controlled Perturbation Experiment (SCoPEX) applied a research governance framework to the SCoPEx proposal detailed in the advisory committee’s final report (Jinnah et al. 2024a), which may inform future governance of outdoor experiments; this framework could potentially be applied to other atmospheric SRM approaches.
      • Specific to Sunshades:
        • There is currently no legal prohibition for climate intervention projects in space (Bodansky 1996). There are some frameworks that provide some guidance for space activities, but they are likely insufficient (Baum et al. 2022). These include:
        • The Outer Space Treaty of 1967 establishes outer space as “the province of all mankind” and establishes open access; any state is free to use space (Bodansky 1996, Baum et al. 2022)
          • Under this treaty, “the exploration and use of outer space … shall be carried out for the benefit and in the interests of all countries, irrespective of their degree of economic or scientific development”.
          • States are to avoid “adverse changes in the environment of the Earth” and are expected to consult with other states about whether an activity might have adverse effects (Bodansky 1996). However, there are no mechanisms for decision-making or resolving disputes (Bodansky 1996).
        • The UN Commission on Peaceful Uses of Outer Space, established by the UN General Assembly in 1959, aims for benefits of space technologies to apply to all countries (Baum et al. 2022).
        • The Environmental Modification Convention is a 1978 UN treaty that “prohibits military or hostile use of environmental modification techniques with widespread, long-lasting, or severe effects” (Baum et al. 2022).
        • See Goguichvili et al. (2021) for an overview on space governance (not specific to climate intervention).

• See DSG (2023), A justice-based analysis of solar geoengineering and capacity building
• Here we define justice related to approaches to slow the loss of Arctic sea ice through distributive justice, procedural justice, and restorative justice. Following COMEST (2023), we consider questions of ethics through a justice lens. Note that this is not an exhaustive list of justice dimensions and as the field advances, so will the related considerations and dimensions.
• Distributive justice
  • Applicable to all approaches within Solar Radiation Modification:
    • Impacts from solar geoengineering have potential to cause disproportionate harm to those least responsible for climate change (DSG 2023). It is also possible that communities most exposed or vulnerable to climate hazards receive the most benefit, depending on the deployment. There is concern from vulnerable populations that research will overlook local needs and worsen global inequities (C2G 2021 Evidence Brief). There is an urgent need for justice-based recommendations (DSG 2023).
  • Specific to Sunshades:
    • Climate intervention in space would have global effects. Recent statements by United States officials claim that space is not a global commons or public good (Sutch and Roberts 2019). The assertion of individual states to rights to space and a race for dominion exacerbates unequal power relations and threatens distributive justice (Sutch and Roberts 2019). Hobe (2007) states that ideas of distributive justice included in Outer Space Treaty are not in practice. Claims about common interest in humanity and environment could be used in international law to reassert commons values in space and to challenge unilateralism (Sutch and Roberts 2019). Deplano (2023) proposes adoption of a proportionality test to guide benefit sharing under the Outer Space Treaty.
• Procedural justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If procedural justice is considered, people affected by research would have an opportunity to participate and have a say in how the approach will be researched, deployed, and governed. Because these approaches have global ramifications, procedural justice will be challenging (Preston 2013).
    • Efforts to support procedural justice for SRM in general to date have been inadequate (DSG 2023). Because of uncertainty in outcomes, variable interests, and the potential for wide-ranging effects, procedural justice is critical (DSG 2023).
    • Diversity within the SRM research community has generally been lacking (NASEM 2021). To address this, some organizations have supported participation in research for the Global South, but there has been a lack of attention on support for participation in governance (DSG 2023). Therefore, organizations and people may understand the science of an approach but not know how to translate their interests around the issue into policy, which is a significant justice gap (DSG 2023).
    • Bennett et al. (2022) suggests an inclusive governance approach that incorporates stakeholder concerns in the design and deployment of approaches and effectively communicates risk. Within the development of such a framework there is an opportunity to prioritize procedural justice (Morrow 2019) and Indigenous self-determination (Chuffart et al. 2023). Note, however, that stakeholders may also include non-local people.
  • Specific to Sunshades:
    • No additional information
• Restorative justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If restorative justice is considered, plans would be developed for those who could be harmed by the approach to be compensated, rehabilitated, or restored (Preston 2013).
    • Horton and Keith (2019) proposed an international climate risk insurance pool where states supporting SRM deployment support the pool and opposing states would be insured against SRM risks.
  • Specific to Sunshades:
    • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There have been a series of open letters from academics and others that reject (Call for Non-Use Agreement) or support (Importance of Research on SRM, Call for Balance) solar radiation modification research, showing the current varying opinions that are shaping public perception.
  • The SCoPEx independent advisory committee offered four core principles for societal engagement related to solar radiation modification:
    • Start engagement efforts as early as possible
    • Include social scientists with engagement expertise on research teams during the research design process
    • Don’t presuppose what communities will be concerned about
    • Develop a plan to be responsive to community concern
  • A recent study on public perceptions found that people surveyed in the Global South were generally more supportive of research and development into SRM technologies compared to those from the Global North (Baum et al. 2024). Those from the Global South also expressed concern about unequal distribution of risks between rich and poor countries (Baum et al. 2024).
• Specific to Sunshades:
  • The public has not really been engaged in this topic (Baum et al. 2022).
  • No assessments of public perception, but one study conducted interviews with experts (Baum et al. 2022).
    • Among experts interviewed by Baum et al. (2022), space-based proposals have several advantages compared to other SRM techniques, such as:
      • not directly interfering with Earth’s biosphere
      • not needing to be redeployed every year (more likely every few decades)
    • The main concerns from experts interviewed by (Baum et al. 2022) included:
      • Concern that space geoengineering is too speculative, therefore resources would be better spent on other activities.
      • The moral hazard argument, as space-based techniques do not address the cause of climate change.
      • Concern that space-based methods won’t be ready for deployment when they would be needed.

• Applicable to all approaches within Solar Radiation Modification:
  • The principle of free, prior, and informed consent (FPIC) in the United Nations Declaration on the Rights of Indigenous Peoples (UNDRIP) is the foundation for engagement with Indigenous Peoples.
  • Particular to any potential Arctic research or deployment, The Inuit Circumpolar Council (2022) has published Circumpolar Inuit Protocols for Equitable and Ethical Engagement, which include eight protocols:
    • ‘Nothing About Us Without Us’ – Always Engage with Inuit
    • Recognize Indigenous Knowledge in its Own Right
    • Practice Good Governance
    • Communication with Intent
    • Exercising Accountability – Building Trust
    • Building Meaningful Partnerships
    • Information, Data Sharing, Ownership, and Permissions
    • Equitably Fund Inuit Representation and Knowledge
  • Any meaningful engagement with Indigenous peoples needs to consider context. Whyte (2018) states, “Indigenous voices should be involved in scientific and policy discussions of different types of geoengineering. But, context matters. Geoengineering discourses cannot just be associated with geoengineering to the exclusion of topics and solutions that Indigenous peoples value.”
• Specific to Sunshades:
  • Unknown
    • It is likely that Indigenous communities have not been engaged in this topic. Article 25 of the UN Declaration on the Rights of Indigenous Peoples (UNDRIP) protects Indigenous lands, specifically those traditionally occupied or used by Indigenous peoples, and does not directly protect any spiritual relationship of Indigenous peoples with outer space (Finnegan 2022). Finnegan (2022) calls for inclusion of Indigenous voices into conversations around international space plans and proposes several avenues.

• Applicable to all approaches within Solar Radiation Modification:
  • International regulations would likely need to be considered for all Solar Radiation Modification approaches as transboundary effects are likely, especially for larger field experiments and deployment, dependent on scale and area of application. Some research activities may fall under national jurisdiction.
• Specific to Sunshades:
  • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There is no formal governance framework for this approach (UNEP 2023). Governance efforts to date have been scattered and ad hoc (NASEM 2021). Governance is needed for at least two different levels: research and deployment (DSG).
    • The National Academy of Sciences’ (2021) report “Reflecting Sunlight: Recommendations for solar geoengineering research and research governance landscape” provides an overview of laws and international treaties that might apply to SRM. These include:
      • Domestic Law
        • US National Environmental Policy Act and state analogs
        • US Weather Modification Reporting Act and state analogs
        • Regulatory statutes
        • Tort Liability
        • Intellectual property law
      • International Environmental Law
        • Treaty Law
          • UN Convention on Biological Diversity
          • London Convention/London Protocol
          • UN Framework Convention on Climate Change
          • Vienna Convention and Montreal Protocol
          • Convention on Long-Range Transboundary Air Pollution (CLRTAP)
          • Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques (ENMOD)
          • UN Convention on the Law of the Sea
        • Customary International Law and Principles
          • Prevention of transboundary harm principle
          • Principle of intergenerational equity
          • The precautionary principle
          • Sustainable development goals
        • It will be important to distinguish small-scale perturbation experiments without climate relevance versus larger-scale testing that may be indistinguishable from deployment.
        • NASEM (2021) provides a proposed framework and approach for SRM research and governance, which emphasis engagement, input, and assessment. This includes exit ramps – “criteria and protocols for terminating research programs or areas” (NASEM 2021).
        • A report by the Climate Overshoot Commission (2023) calls for research on SRM and governance discussions as well as moratorium on SRM deployment and large-scale outdoor experiments.
        • UNESCO World Commission on the Ethics of Scientific Knowledge and Technology’s (COMEST) 2023 Report on the ethics of climate engineering has a slate of recommendations related to SRM covering governance, participation and inclusion, role of scientific knowledge and research strengthening capacity, and education, awareness, and advocacy.
        • In the absence of a governance framework there have been calls for governments to prohibit the development and deployment of SRM (Gupta et al. 2024). There is a need for governments to discuss coordination of research governance (Jinnah et al. 2024b).
        • An independent advisory committee for Harvard University’s Stratospheric Controlled Perturbation Experiment (SCoPEX) applied a research governance framework to the SCoPEx proposal detailed in the advisory committee’s final report (Jinnah et al. 2024a), which may inform future governance of outdoor experiments; this framework could potentially be applied to other atmospheric SRM approaches.
      • Specific to Sunshades:
        • There is currently no legal prohibition for climate intervention projects in space (Bodansky 1996). There are some frameworks that provide some guidance for space activities, but they are likely insufficient (Baum et al. 2022). These include:
        • The Outer Space Treaty of 1967 establishes outer space as “the province of all mankind” and establishes open access; any state is free to use space (Bodansky 1996, Baum et al. 2022)
          • Under this treaty, “the exploration and use of outer space … shall be carried out for the benefit and in the interests of all countries, irrespective of their degree of economic or scientific development”.
          • States are to avoid “adverse changes in the environment of the Earth” and are expected to consult with other states about whether an activity might have adverse effects (Bodansky 1996). However, there are no mechanisms for decision-making or resolving disputes (Bodansky 1996).
        • The UN Commission on Peaceful Uses of Outer Space, established by the UN General Assembly in 1959, aims for benefits of space technologies to apply to all countries (Baum et al. 2022).
        • The Environmental Modification Convention is a 1978 UN treaty that “prohibits military or hostile use of environmental modification techniques with widespread, long-lasting, or severe effects” (Baum et al. 2022).
        • See Goguichvili et al. (2021) for an overview on space governance (not specific to climate intervention).

• See DSG (2023), A justice-based analysis of solar geoengineering and capacity building
• Here we define justice related to approaches to slow the loss of Arctic sea ice through distributive justice, procedural justice, and restorative justice. Following COMEST (2023), we consider questions of ethics through a justice lens. Note that this is not an exhaustive list of justice dimensions and as the field advances, so will the related considerations and dimensions.
• Distributive justice
  • Applicable to all approaches within Solar Radiation Modification:
    • Impacts from solar geoengineering have potential to cause disproportionate harm to those least responsible for climate change (DSG 2023). It is also possible that communities most exposed or vulnerable to climate hazards receive the most benefit, depending on the deployment. There is concern from vulnerable populations that research will overlook local needs and worsen global inequities (C2G 2021 Evidence Brief). There is an urgent need for justice-based recommendations (DSG 2023).
  • Specific to Sunshades:
    • Climate intervention in space would have global effects. Recent statements by United States officials claim that space is not a global commons or public good (Sutch and Roberts 2019). The assertion of individual states to rights to space and a race for dominion exacerbates unequal power relations and threatens distributive justice (Sutch and Roberts 2019). Hobe (2007) states that ideas of distributive justice included in Outer Space Treaty are not in practice. Claims about common interest in humanity and environment could be used in international law to reassert commons values in space and to challenge unilateralism (Sutch and Roberts 2019). Deplano (2023) proposes adoption of a proportionality test to guide benefit sharing under the Outer Space Treaty.
• Procedural justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If procedural justice is considered, people affected by research would have an opportunity to participate and have a say in how the approach will be researched, deployed, and governed. Because these approaches have global ramifications, procedural justice will be challenging (Preston 2013).
    • Efforts to support procedural justice for SRM in general to date have been inadequate (DSG 2023). Because of uncertainty in outcomes, variable interests, and the potential for wide-ranging effects, procedural justice is critical (DSG 2023).
    • Diversity within the SRM research community has generally been lacking (NASEM 2021). To address this, some organizations have supported participation in research for the Global South, but there has been a lack of attention on support for participation in governance (DSG 2023). Therefore, organizations and people may understand the science of an approach but not know how to translate their interests around the issue into policy, which is a significant justice gap (DSG 2023).
    • Bennett et al. (2022) suggests an inclusive governance approach that incorporates stakeholder concerns in the design and deployment of approaches and effectively communicates risk. Within the development of such a framework there is an opportunity to prioritize procedural justice (Morrow 2019) and Indigenous self-determination (Chuffart et al. 2023). Note, however, that stakeholders may also include non-local people.
  • Specific to Sunshades:
    • No additional information
• Restorative justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If restorative justice is considered, plans would be developed for those who could be harmed by the approach to be compensated, rehabilitated, or restored (Preston 2013).
    • Horton and Keith (2019) proposed an international climate risk insurance pool where states supporting SRM deployment support the pool and opposing states would be insured against SRM risks.
  • Specific to Sunshades:
    • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There have been a series of open letters from academics and others that reject (Call for Non-Use Agreement) or support (Importance of Research on SRM, Call for Balance) solar radiation modification research, showing the current varying opinions that are shaping public perception.
  • The SCoPEx independent advisory committee offered four core principles for societal engagement related to solar radiation modification:
    • Start engagement efforts as early as possible
    • Include social scientists with engagement expertise on research teams during the research design process
    • Don’t presuppose what communities will be concerned about
    • Develop a plan to be responsive to community concern
  • A recent study on public perceptions found that people surveyed in the Global South were generally more supportive of research and development into SRM technologies compared to those from the Global North (Baum et al. 2024). Those from the Global South also expressed concern about unequal distribution of risks between rich and poor countries (Baum et al. 2024).
• Specific to Sunshades:
  • The public has not really been engaged in this topic (Baum et al. 2022).
  • No assessments of public perception, but one study conducted interviews with experts (Baum et al. 2022).
    • Among experts interviewed by Baum et al. (2022), space-based proposals have several advantages compared to other SRM techniques, such as:
      • not directly interfering with Earth’s biosphere
      • not needing to be redeployed every year (more likely every few decades)
    • The main concerns from experts interviewed by (Baum et al. 2022) included:
      • Concern that space geoengineering is too speculative, therefore resources would be better spent on other activities.
      • The moral hazard argument, as space-based techniques do not address the cause of climate change.
      • Concern that space-based methods won’t be ready for deployment when they would be needed.

• Applicable to all approaches within Solar Radiation Modification:
  • The principle of free, prior, and informed consent (FPIC) in the United Nations Declaration on the Rights of Indigenous Peoples (UNDRIP) is the foundation for engagement with Indigenous Peoples.
  • Particular to any potential Arctic research or deployment, The Inuit Circumpolar Council (2022) has published Circumpolar Inuit Protocols for Equitable and Ethical Engagement, which include eight protocols:
    • ‘Nothing About Us Without Us’ – Always Engage with Inuit
    • Recognize Indigenous Knowledge in its Own Right
    • Practice Good Governance
    • Communication with Intent
    • Exercising Accountability – Building Trust
    • Building Meaningful Partnerships
    • Information, Data Sharing, Ownership, and Permissions
    • Equitably Fund Inuit Representation and Knowledge
  • Any meaningful engagement with Indigenous peoples needs to consider context. Whyte (2018) states, “Indigenous voices should be involved in scientific and policy discussions of different types of geoengineering. But, context matters. Geoengineering discourses cannot just be associated with geoengineering to the exclusion of topics and solutions that Indigenous peoples value.”
• Specific to Sunshades:
  • Unknown
    • It is likely that Indigenous communities have not been engaged in this topic. Article 25 of the UN Declaration on the Rights of Indigenous Peoples (UNDRIP) protects Indigenous lands, specifically those traditionally occupied or used by Indigenous peoples, and does not directly protect any spiritual relationship of Indigenous peoples with outer space (Finnegan 2022). Finnegan (2022) calls for inclusion of Indigenous voices into conversations around international space plans and proposes several avenues.

• Applicable to all approaches within Solar Radiation Modification:
  • International regulations would likely need to be considered for all Solar Radiation Modification approaches as transboundary effects are likely, especially for larger field experiments and deployment, dependent on scale and area of application. Some research activities may fall under national jurisdiction.
• Specific to Sunshades:
  • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There is no formal governance framework for this approach (UNEP 2023). Governance efforts to date have been scattered and ad hoc (NASEM 2021). Governance is needed for at least two different levels: research and deployment (DSG).
    • The National Academy of Sciences’ (2021) report “Reflecting Sunlight: Recommendations for solar geoengineering research and research governance landscape” provides an overview of laws and international treaties that might apply to SRM. These include:
      • Domestic Law
        • US National Environmental Policy Act and state analogs
        • US Weather Modification Reporting Act and state analogs
        • Regulatory statutes
        • Tort Liability
        • Intellectual property law
      • International Environmental Law
        • Treaty Law
          • UN Convention on Biological Diversity
          • London Convention/London Protocol
          • UN Framework Convention on Climate Change
          • Vienna Convention and Montreal Protocol
          • Convention on Long-Range Transboundary Air Pollution (CLRTAP)
          • Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques (ENMOD)
          • UN Convention on the Law of the Sea
        • Customary International Law and Principles
          • Prevention of transboundary harm principle
          • Principle of intergenerational equity
          • The precautionary principle
          • Sustainable development goals
        • It will be important to distinguish small-scale perturbation experiments without climate relevance versus larger-scale testing that may be indistinguishable from deployment.
        • NASEM (2021) provides a proposed framework and approach for SRM research and governance, which emphasis engagement, input, and assessment. This includes exit ramps – “criteria and protocols for terminating research programs or areas” (NASEM 2021).
        • A report by the Climate Overshoot Commission (2023) calls for research on SRM and governance discussions as well as moratorium on SRM deployment and large-scale outdoor experiments.
        • UNESCO World Commission on the Ethics of Scientific Knowledge and Technology’s (COMEST) 2023 Report on the ethics of climate engineering has a slate of recommendations related to SRM covering governance, participation and inclusion, role of scientific knowledge and research strengthening capacity, and education, awareness, and advocacy.
        • In the absence of a governance framework there have been calls for governments to prohibit the development and deployment of SRM (Gupta et al. 2024). There is a need for governments to discuss coordination of research governance (Jinnah et al. 2024b).
        • An independent advisory committee for Harvard University’s Stratospheric Controlled Perturbation Experiment (SCoPEX) applied a research governance framework to the SCoPEx proposal detailed in the advisory committee’s final report (Jinnah et al. 2024a), which may inform future governance of outdoor experiments; this framework could potentially be applied to other atmospheric SRM approaches.
      • Specific to Sunshades:
        • There is currently no legal prohibition for climate intervention projects in space (Bodansky 1996). There are some frameworks that provide some guidance for space activities, but they are likely insufficient (Baum et al. 2022). These include:
        • The Outer Space Treaty of 1967 establishes outer space as “the province of all mankind” and establishes open access; any state is free to use space (Bodansky 1996, Baum et al. 2022)
          • Under this treaty, “the exploration and use of outer space … shall be carried out for the benefit and in the interests of all countries, irrespective of their degree of economic or scientific development”.
          • States are to avoid “adverse changes in the environment of the Earth” and are expected to consult with other states about whether an activity might have adverse effects (Bodansky 1996). However, there are no mechanisms for decision-making or resolving disputes (Bodansky 1996).
        • The UN Commission on Peaceful Uses of Outer Space, established by the UN General Assembly in 1959, aims for benefits of space technologies to apply to all countries (Baum et al. 2022).
        • The Environmental Modification Convention is a 1978 UN treaty that “prohibits military or hostile use of environmental modification techniques with widespread, long-lasting, or severe effects” (Baum et al. 2022).
        • See Goguichvili et al. (2021) for an overview on space governance (not specific to climate intervention).

• See DSG (2023), A justice-based analysis of solar geoengineering and capacity building
• Here we define justice related to approaches to slow the loss of Arctic sea ice through distributive justice, procedural justice, and restorative justice. Following COMEST (2023), we consider questions of ethics through a justice lens. Note that this is not an exhaustive list of justice dimensions and as the field advances, so will the related considerations and dimensions.
• Distributive justice
  • Applicable to all approaches within Solar Radiation Modification:
    • Impacts from solar geoengineering have potential to cause disproportionate harm to those least responsible for climate change (DSG 2023). It is also possible that communities most exposed or vulnerable to climate hazards receive the most benefit, depending on the deployment. There is concern from vulnerable populations that research will overlook local needs and worsen global inequities (C2G 2021 Evidence Brief). There is an urgent need for justice-based recommendations (DSG 2023).
  • Specific to Sunshades:
    • Climate intervention in space would have global effects. Recent statements by United States officials claim that space is not a global commons or public good (Sutch and Roberts 2019). The assertion of individual states to rights to space and a race for dominion exacerbates unequal power relations and threatens distributive justice (Sutch and Roberts 2019). Hobe (2007) states that ideas of distributive justice included in Outer Space Treaty are not in practice. Claims about common interest in humanity and environment could be used in international law to reassert commons values in space and to challenge unilateralism (Sutch and Roberts 2019). Deplano (2023) proposes adoption of a proportionality test to guide benefit sharing under the Outer Space Treaty.
• Procedural justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If procedural justice is considered, people affected by research would have an opportunity to participate and have a say in how the approach will be researched, deployed, and governed. Because these approaches have global ramifications, procedural justice will be challenging (Preston 2013).
    • Efforts to support procedural justice for SRM in general to date have been inadequate (DSG 2023). Because of uncertainty in outcomes, variable interests, and the potential for wide-ranging effects, procedural justice is critical (DSG 2023).
    • Diversity within the SRM research community has generally been lacking (NASEM 2021). To address this, some organizations have supported participation in research for the Global South, but there has been a lack of attention on support for participation in governance (DSG 2023). Therefore, organizations and people may understand the science of an approach but not know how to translate their interests around the issue into policy, which is a significant justice gap (DSG 2023).
    • Bennett et al. (2022) suggests an inclusive governance approach that incorporates stakeholder concerns in the design and deployment of approaches and effectively communicates risk. Within the development of such a framework there is an opportunity to prioritize procedural justice (Morrow 2019) and Indigenous self-determination (Chuffart et al. 2023). Note, however, that stakeholders may also include non-local people.
  • Specific to Sunshades:
    • No additional information
• Restorative justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If restorative justice is considered, plans would be developed for those who could be harmed by the approach to be compensated, rehabilitated, or restored (Preston 2013).
    • Horton and Keith (2019) proposed an international climate risk insurance pool where states supporting SRM deployment support the pool and opposing states would be insured against SRM risks.
  • Specific to Sunshades:
    • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There have been a series of open letters from academics and others that reject (Call for Non-Use Agreement) or support (Importance of Research on SRM, Call for Balance) solar radiation modification research, showing the current varying opinions that are shaping public perception.
  • The SCoPEx independent advisory committee offered four core principles for societal engagement related to solar radiation modification:
    • Start engagement efforts as early as possible
    • Include social scientists with engagement expertise on research teams during the research design process
    • Don’t presuppose what communities will be concerned about
    • Develop a plan to be responsive to community concern
  • A recent study on public perceptions found that people surveyed in the Global South were generally more supportive of research and development into SRM technologies compared to those from the Global North (Baum et al. 2024). Those from the Global South also expressed concern about unequal distribution of risks between rich and poor countries (Baum et al. 2024).
• Specific to Sunshades:
  • The public has not really been engaged in this topic (Baum et al. 2022).
  • No assessments of public perception, but one study conducted interviews with experts (Baum et al. 2022)
    • Among experts interviewed by Baum et al. (2022), space-based proposals have several advantages compared to other SRM techniques, such as:
      • not directly interfering with Earth’s biosphere
      • not needing to be redeployed every year (more likely every few decades)
    • The main concerns from experts interviewed by (Baum et al. 2022) included:
      • Concern that space geoengineering is too speculative, therefore resources would be better spent on other activities
      • The moral hazard argument, as space-based techniques do not address the cause of climate change
      • Concern that space-based methods won’t be ready for deployment when they would be needed.

• Applicable to all approaches within Solar Radiation Modification:
  • The principle of free, prior, and informed consent (FPIC) in the United Nations Declaration on the Rights of Indigenous Peoples (UNDRIP) is the foundation for engagement with Indigenous Peoples.
  • Particular to any potential Arctic research or deployment, The Inuit Circumpolar Council (2022) has published Circumpolar Inuit Protocols for Equitable and Ethical Engagement, which include eight protocols:
    • ‘Nothing About Us Without Us’ – Always Engage with Inuit
    • Recognize Indigenous Knowledge in its Own Right
    • Practice Good Governance
    • Communication with Intent
    • Exercising Accountability – Building Trust
    • Building Meaningful Partnerships
    • Information, Data Sharing, Ownership, and Permissions
    • Equitably Fund Inuit Representation and Knowledge
  • Any meaningful engagement with Indigenous peoples needs to consider context. Whyte (2018) states, “Indigenous voices should be involved in scientific and policy discussions of different types of geoengineering. But, context matters. Geoengineering discourses cannot just be associated with geoengineering to the exclusion of topics and solutions that Indigenous peoples value.”
• Specific to Sunshades:
  • Unknown
    • It is likely that Indigenous communities have not been engaged in this topic. Article 25 of the UN Declaration on the Rights of Indigenous Peoples (UNDRIP) protects Indigenous lands, specifically those traditionally occupied or used by Indigenous peoples, and does not directly protect any spiritual relationship of Indigenous peoples with outer space (Finnegan 2022). Finnegan (2022) calls for inclusion of Indigenous voices into conversations around international space plans and proposes several avenues.

• Applicable to all approaches within Solar Radiation Modification:
  • International regulations would likely need to be considered for all Solar Radiation Modification approaches as transboundary effects are likely, especially for larger field experiments and deployment, dependent on scale and area of application. Some research activities may fall under national jurisdiction.
• Specific to Sunshades:
  • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There is no formal governance framework for this approach (UNEP 2023). Governance efforts to date have been scattered and ad hoc (NASEM 2021). Governance is needed for at least two different levels: research and deployment (DSG).
    • The National Academy of Sciences’ (2021) report “Reflecting Sunlight: Recommendations for solar geoengineering research and research governance landscape” provides an overview of laws and international treaties that might apply to SRM. These include:
      • Domestic Law
        • US National Environmental Policy Act and state analogs
        • US Weather Modification Reporting Act and state analogs
        • Regulatory statutes
        • Tort Liability
        • Intellectual property law
      • International Environmental Law
        • Treaty Law
          • UN Convention on Biological Diversity
          • London Convention/London Protocol
          • UN Framework Convention on Climate Change
          • Vienna Convention and Montreal Protocol
          • Convention on Long-Range Transboundary Air Pollution (CLRTAP)
          • Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques (ENMOD)
          • UN Convention on the Law of the Sea
        • Customary International Law and Principles
          • Prevention of transboundary harm principle
          • Principle of intergenerational equity
          • The precautionary principle
          • Sustainable development goals
        • It will be important to distinguish small-scale perturbation experiments without climate relevance versus larger-scale testing that may be indistinguishable from deployment.
        • NASEM (2021) provides a proposed framework and approach for SRM research and governance, which emphasis engagement, input, and assessment. This includes exit ramps – “criteria and protocols for terminating research programs or areas” (NASEM 2021).
        • A report by the Climate Overshoot Commission (2023) calls for research on SRM and governance discussions as well as moratorium on SRM deployment and large-scale outdoor experiments.
        • UNESCO World Commission on the Ethics of Scientific Knowledge and Technology’s (COMEST) 2023 Report on the ethics of climate engineering has a slate of recommendations related to SRM covering governance, participation and inclusion, role of scientific knowledge and research strengthening capacity, and education, awareness, and advocacy.
        • In the absence of a governance framework there have been calls for governments to prohibit the development and deployment of SRM (Gupta et al. 2024). There is a need for governments to discuss coordination of research governance (Jinnah et al. 2024b).
        • An independent advisory committee for Harvard University’s Stratospheric Controlled Perturbation Experiment (SCoPEX) applied a research governance framework to the SCoPEx proposal detailed in the advisory committee’s final report (Jinnah et al. 2024a), which may inform future governance of outdoor experiments; this framework could potentially be applied to other atmospheric SRM approaches.
      • Specific to Sunshades:
        • There is currently no legal prohibition for climate intervention projects in space (Bodansky 1996). There are some frameworks that provide some guidance for space activities, but they are likely insufficient (Baum et al. 2022). These include:
        • The Outer Space Treaty of 1967 establishes outer space as “the province of all mankind” and establishes open access; any state is free to use space (Bodansky 1996, Baum et al. 2022)
          • Under this treaty, “the exploration and use of outer space … shall be carried out for the benefit and in the interests of all countries, irrespective of their degree of economic or scientific development”.
          • States are to avoid “adverse changes in the environment of the Earth” and are expected to consult with other states about whether an activity might have adverse effects (Bodansky 1996). However, there are no mechanisms for decision-making or resolving disputes (Bodansky 1996).
        • The UN Commission on Peaceful Uses of Outer Space, established by the UN General Assembly in 1959, aims for benefits of space technologies to apply to all countries (Baum et al. 2022).
        • The Environmental Modification Convention is a 1978 UN treaty that “prohibits military or hostile use of environmental modification techniques with widespread, long-lasting, or severe effects” (Baum et al. 2022).
        • See Goguichvili et al. (2021) for an overview on space governance (not specific to climate intervention).

• See DSG (2023), A justice-based analysis of solar geoengineering and capacity building
• Here we define justice related to approaches to slow the loss of Arctic sea ice through distributive justice, procedural justice, and restorative justice. Following COMEST (2023), we consider questions of ethics through a justice lens. Note that this is not an exhaustive list of justice dimensions and as the field advances, so will the related considerations and dimensions.
• Distributive justice
  • Applicable to all approaches within Solar Radiation Modification:
    • Impacts from solar geoengineering have potential to cause disproportionate harm to those least responsible for climate change (DSG 2023). It is also possible that communities most exposed or vulnerable to climate hazards receive the most benefit, depending on the deployment. There is concern from vulnerable populations that research will overlook local needs and worsen global inequities (C2G 2021 Evidence Brief). There is an urgent need for justice-based recommendations (DSG 2023).
  • Specific to Sunshades:
    • Climate intervention in space would have global effects. Recent statements by United States officials claim that space is not a global commons or public good (Sutch and Roberts 2019). The assertion of individual states to rights to space and a race for dominion exacerbates unequal power relations and threatens distributive justice (Sutch and Roberts 2019). Hobe (2007) states that ideas of distributive justice included in Outer Space Treaty are not in practice. Claims about common interest in humanity and environment could be used in international law to reassert commons values in space and to challenge unilateralism (Sutch and Roberts 2019). Deplano (2023) proposes adoption of a proportionality test to guide benefit sharing under the Outer Space Treaty.
• Procedural justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If procedural justice is considered, people affected by research would have an opportunity to participate and have a say in how the approach will be researched, deployed, and governed. Because these approaches have global ramifications, procedural justice will be challenging (Preston 2013).
    • Efforts to support procedural justice for SRM in general to date have been inadequate (DSG 2023). Because of uncertainty in outcomes, variable interests, and the potential for wide-ranging effects, procedural justice is critical (DSG 2023).
    • Diversity within the SRM research community has generally been lacking (NASEM 2021). To address this, some organizations have supported participation in research for the Global South, but there has been a lack of attention on support for participation in governance (DSG 2023). Therefore, organizations and people may understand the science of an approach but not know how to translate their interests around the issue into policy, which is a significant justice gap (DSG 2023).
    • Bennett et al. (2022) suggests an inclusive governance approach that incorporates stakeholder concerns in the design and deployment of approaches and effectively communicates risk. Within the development of such a framework there is an opportunity to prioritize Indigenous self-determination and procedural justice (Chuffart et al. 2023). Note, however, that stakeholders may also include non-local people.
  • Specific to Sunshades:
    • No additional information
• Restorative justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If restorative justice is considered, plans would be developed for those who could be harmed by the approach to be compensated, rehabilitated, or restored (Preston 2013).
    • Horton and Keith (2019) proposed an international climate risk insurance pool where states supporting SRM deployment support the pool and opposing states would be insured against SRM risks.
  • Specific to Sunshades:
    • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There have been a series of open letters from academics and others that reject (Call for Non-Use Agreement) or support (Importance of Research on SRM, Call for Balance) solar radiation modification research, showing the current varying opinions that are shaping public perception.
  • The SCoPEx independent advisory committee offered four core principles for societal engagement related to solar radiation modification:
    • Start engagement efforts as early as possible
    • Include social scientists with engagement expertise on research teams during the research design process
    • Don’t presuppose what communities will be concerned about
    • Develop a plan to be responsive to community concern
  • A recent study on public perceptions found that people surveyed in the Global South were generally more supportive of research and development into SRM technologies compared to those from the Global North (Baum et al. 2024). Those from the Global South also expressed concern about unequal distribution of risks between rich and poor countries (Baum et al. 2024).
• Specific to Sunshades:
  • The public has not really been engaged in this topic (Baum et al. 2022).
  • No assessments of public perception, but one study conducted interviews with experts (Baum et al. 2022)
    • Among experts interviewed by Baum et al. (2022), space-based proposals have several advantages compared to other SRM techniques, such as:
      • not directly interfering with Earth’s biosphere
      • not needing to be redeployed every year (more likely every few decades)
    • The main concerns from experts interviewed by (Baum et al. 2022) included:
      • Concern that space geoengineering is too speculative, therefore resources would be better spent on other activities
      • The moral hazard argument, as space-based techniques do not address the cause of climate change
      • Concern that space-based methods won’t be ready for deployment when they would be needed.

• Applicable to all approaches within Solar Radiation Modification:
  • The principle of free, prior, and informed consent (FPIC) in the United Nations Declaration on the Rights of Indigenous Peoples (UNDRIP) is the foundation for engagement with Indigenous Peoples.
  • Particular to any potential Arctic research or deployment, The Inuit Circumpolar Council (2022) has published Circumpolar Inuit Protocols for Equitable and Ethical Engagement, which include eight protocols:
    • ‘Nothing About Us Without Us’ – Always Engage with Inuit
    • Recognize Indigenous Knowledge in its Own Right
    • Practice Good Governance
    • Communication with Intent
    • Exercising Accountability – Building Trust
    • Building Meaningful Partnerships
    • Information, Data Sharing, Ownership, and Permissions
    • Equitably Fund Inuit Representation and Knowledge
  • Any meaningful engagement with Indigenous peoples needs to consider context. Whyte (2018) states, “Indigenous voices should be involved in scientific and policy discussions of different types of geoengineering. But, context matters. Geoengineering discourses cannot just be associated with geoengineering to the exclusion of topics and solutions that Indigenous peoples value.”
• Specific to Sunshades:
  • Unknown
    • It is likely that Indigenous communities have not been engaged in this topic. Article 25 of the UN Declaration on the Rights of Indigenous Peoples (UNDRIP) protects Indigenous lands, specifically those traditionally occupied or used by Indigenous peoples, and does not directly protect any spiritual relationship of Indigenous peoples with outer space (Finnegan 2022). Finnegan (2022) calls for inclusion of Indigenous voices into conversations around international space plans and proposes several avenues.

• Applicable to all approaches within Solar Radiation Modification:
  • International regulations would likely need to be considered for all Solar Radiation Modification approaches as transboundary effects are likely, especially for larger field experiments and deployment, dependent on scale and area of application. Some research activities may fall under national jurisdiction.
• Specific to Sunshades:
  • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There is no formal governance framework for this approach (UNEP 2023). Governance efforts to date have been scattered and ad hoc (NASEM 2021). Governance is needed for at least two different levels: research and deployment (DSG).
    • The National Academy of Sciences’ (2021) report “Reflecting Sunlight: Recommendations for solar geoengineering research and research governance landscape” provides an overview of laws and international treaties that might apply to SRM. These include:
      • Domestic Law
        • US National Environmental Policy Act and state analogs
        • US Weather Modification Reporting Act and state analogs
        • Regulatory statutes
        • Tort Liability
        • Intellectual property law
      • International Environmental Law
        • Treaty Law
          • UN Convention on Biological Diversity
          • London Convention/London Protocol
          • UN Framework Convention on Climate Change
          • Vienna Convention and Montreal Protocol
          • Convention on Long-Range Transboundary Air Pollution (CLRTAP)
          • Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques (ENMOD)
          • UN Convention on the Law of the Sea
        • Customary International Law and Principles
          • Prevention of transboundary harm principle
          • Principle of intergenerational equity
          • The precautionary principle
          • Sustainable development goals
        • It will be important to distinguish small-scale perturbation experiments without climate relevance versus larger-scale testing that may be indistinguishable from deployment.
        • NASEM (2021) provides a proposed framework and approach for SRM research and governance, which emphasis engagement, input, and assessment. This includes exit ramps – “criteria and protocols for terminating research programs or areas” (NASEM 2021).
        • A report by the Climate Overshoot Commission (2023) calls for research on SRM and governance discussions as well as moratorium on SRM deployment and large-scale outdoor experiments.
        • UNESCO World Commission on the Ethics of Scientific Knowledge and Technology’s (COMEST) 2023 Report on the ethics of climate engineering has a slate of recommendations related to SRM covering governance, participation and inclusion, role of scientific knowledge and research strengthening capacity, and education, awareness, and advocacy.
        • In the absence of a governance framework there have been calls for governments to prohibit the development and deployment of SRM (Gupta et al. 2024). There is a need for governments to discuss coordination of research governance (Jinnah et al. 2024b).
        • An independent advisory committee for Harvard University’s Stratospheric Controlled Perturbation Experiment (SCoPEX) applied a research governance framework to the SCoPEx proposal detailed in the advisory committee’s final report (Jinnah et al. 2024a), which may inform future governance of outdoor experiments; this framework could potentially be applied to other atmospheric SRM approaches.
      • Specific to Sunshades:
        • There is currently no legal prohibition for climate intervention projects in space (Bodansky 1996). There are some frameworks that provide some guidance for space activities, but they are likely insufficient (Baum et al. 2022). These include:
        • The Outer Space Treaty of 1967 establishes outer space as “the province of all mankind” and establishes open access; any state is free to use space (Bodansky 1996, Baum et al. 2022)
          • Under this treaty, “the exploration and use of outer space … shall be carried out for the benefit and in the interests of all countries, irrespective of their degree of economic or scientific development”.
          • States are to avoid “adverse changes in the environment of the Earth” and are expected to consult with other states about whether an activity might have adverse effects (Bodansky 1996). However, there are no mechanisms for decision-making or resolving disputes (Bodansky 1996).
        • The UN Commission on Peaceful Uses of Outer Space, established by the UN General Assembly in 1959, aims for benefits of space technologies to apply to all countries (Baum et al. 2022).
        • The Environmental Modification Convention is a 1978 UN treaty that “prohibits military or hostile use of environmental modification techniques with widespread, long-lasting, or severe effects” (Baum et al. 2022).
        • See Goguichvili et al. (2021) for an overview on space governance (not specific to climate intervention).

• See DSG (2023), A justice-based analysis of solar geoengineering and capacity building
• Here we define justice related to approaches to slow the loss of Arctic sea ice through distributive justice, procedural justice, and restorative justice. Following COMEST (2023), we consider questions of ethics through a justice lens. Note that this is not an exhaustive list of justice dimensions and as the field advances, so will the related considerations and dimensions.
• Distributive justice
  • Applicable to all approaches within Solar Radiation Modification:
    • Impacts from solar geoengineering have potential to cause disproportionate harm to those least responsible for climate change (DSG 2023). It is also possible that communities most exposed or vulnerable to climate hazards receive the most benefit, depending on the deployment. There is concern from vulnerable populations that research will overlook local needs and worsen global inequities (C2G 2021 Evidence Brief). There is an urgent need for justice-based recommendations (DSG 2023).
  • Specific to Sunshades:
    • Climate intervention in space would have global effects. Recent statements by United States officials claim that space is not a global commons or public good (Sutch and Roberts 2019). The assertion of individual states to rights to space and a race for dominion exacerbates unequal power relations and threatens distributive justice (Sutch and Roberts 2019). Hobe (2007) states that ideas of distributive justice included in Outer Space Treaty are not in practice. Claims about common interest in humanity and environment could be used in international law to reassert commons values in space and to challenge unilateralism (Sutch and Roberts 2019). Deplano (2023) proposes adoption of a proportionality test to guide benefit sharing under the Outer Space Treaty.
• Procedural justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If procedural justice is considered, people affected by research would have an opportunity to participate and have a say in how the approach will be researched, deployed, and governed. Because these approaches have global ramifications, procedural justice will be challenging (Preston 2013).
    • Efforts to support procedural justice for SRM in general to date have been inadequate (DSG 2023). Because of uncertainty in outcomes, variable interests, and the potential for wide-ranging effects, procedural justice is critical (DSG 2023).
    • Diversity within the SRM research community has generally been lacking (NASEM 2021). To address this, some organizations have supported participation in research for the Global South, but there has been a lack of attention on support for participation in governance (DSG 2023). Therefore, organizations and people may understand the science of an approach but not know how to translate their interests around the issue into policy, which is a significant justice gap (DSG 2023).
    • Bennett et al. (2022) suggests an inclusive governance approach that incorporates stakeholder concerns in the design and deployment of approaches and effectively communicates risk. Within the development of such a framework there is an opportunity to prioritize Indigenous self-determination and procedural justice (Chuffart et al. 2023). Note, however, that stakeholders may also include non-local people.
  • Specific to Sunshades:
    • No additional information
• Restorative justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If restorative justice is considered, plans would be developed for those who could be harmed by the approach to be compensated, rehabilitated, or restored (Preston 2013).
    • Horton and Keith (2019) proposed an international climate risk insurance pool where states supporting SRM deployment support the pool and opposing states would be insured against SRM risks.
  • Specific to Sunshades:
    • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There have been a series of open letters from academics and others that reject (Call for Non-Use Agreement) or support (Importance of Research on SRM, Call for Balance) solar radiation modification research, showing the current varying opinions that are shaping public perception.
  • The SCoPEx independent advisory committee offered four core principles for societal engagement related to solar radiation modification:
    • Start engagement efforts as early as possible
    • Include social scientists with engagement expertise on research teams during the research design process
    • Don’t presuppose what communities will be concerned about
    • Develop a plan to be responsive to community concern
  • A recent study on public perceptions found that people surveyed in the Global South were generally more supportive of research and development into SRM technologies compared to those from the Global North (Baum et al. 2024). Those from the Global South also expressed concern about unequal distribution of risks between rich and poor countries (Baum et al. 2024).
• Specific to Sunshades:
  • The public has not really been engaged in this topic (Baum et al. 2022).
  • No assessments of public perception, but one study conducted interviews with experts (Baum et al. 2022)
    • Among experts interviewed by Baum et al. (2022), space-based proposals have several advantages compared to other SRM techniques, such as:
      • not directly interfering with Earth’s biosphere
      • not needing to be redeployed every year (more likely every few decades)
    • The main concerns from experts interviewed by (Baum et al. 2022) included:
      • Concern that space geoengineering is too speculative, therefore resources would be better spent on other activities
      • The moral hazard argument, as space-based techniques do not address the cause of climate change
      • Concern that space-based methods won’t be ready for deployment when they would be needed.

• Applicable to all approaches within Solar Radiation Modification:
  • The principle of free, prior, and informed consent (FPIC) in the United Nations Declaration on the Rights of Indigenous Peoples (UNDRIP) is the foundation for engagement with Indigenous Peoples.
  • Particular to any potential Arctic research or deployment, The Inuit Circumpolar Council (2022) has published Circumpolar Inuit Protocols for Equitable and Ethical Engagement, which include eight protocols:
    • ‘Nothing About Us Without Us’ – Always Engage with Inuit
    • Recognize Indigenous Knowledge in its Own Right
    • Practice Good Governance
    • Communication with Intent
    • Exercising Accountability – Building Trust
    • Building Meaningful Partnerships
    • Information, Data Sharing, Ownership, and Permissions
    • Equitably Fund Inuit Representation and Knowledge
  • Any meaningful engagement with Indigenous peoples needs to consider context. Whyte (2018) states, “Indigenous voices should be involved in scientific and policy discussions of different types of geoengineering. But, context matters. Geoengineering discourses cannot just be associated with geoengineering to the exclusion of topics and solutions that Indigenous peoples value.”
• Specific to Sunshades:
  • Unknown
    • It is likely that Indigenous communities have not been engaged in this topic. Article 25 of the UN Declaration on the Rights of Indigenous Peoples (UNDRIP) protects Indigenous lands, specifically those traditionally occupied or used by Indigenous peoples, and does not directly protect any spiritual relationship of Indigenous peoples with outer space (Finnegan 2022). Finnegan (2022) calls for inclusion of Indigenous voices into conversations around international space plans and proposes several avenues.

• Applicable to all approaches within Solar Radiation Modification:
  • International regulations would likely need to be considered for all Solar Radiation Modification approaches as transboundary effects are likely, especially for larger field experiments and deployment, dependent on scale and area of application. Some research activities may fall under national jurisdiction.
• Specific to Sunshades:
  • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There is no formal governance framework for this approach (UNEP 2023). Governance efforts to date have been scattered and ad hoc (NASEM 2021). Governance is needed for at least two different levels: research and deployment (DSG).
    • The National Academy of Sciences’ (2021) report “Reflecting Sunlight: Recommendations for solar geoengineering research and research governance landscape” provides an overview of laws and international treaties that might apply to SRM. These include:
      • Domestic Law
        • US National Environmental Policy Act and state analogs
        • US Weather Modification Reporting Act and state analogs
        • Regulatory statutes
        • Tort Liability
        • Intellectual property law
      • International Environmental Law
        • Treaty Law
          • UN Convention on Biological Diversity
          • London Convention/London Protocol
          • UN Framework Convention on Climate Change
          • Vienna Convention and Montreal Protocol
          • Convention on Long-Range Transboundary Air Pollution (CLRTAP)
          • Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques (ENMOD)
          • UN Convention on the Law of the Sea
        • Customary International Law and Principles
          • Prevention of transboundary harm principle
          • Principle of intergenerational equity
          • The precautionary principle
          • Sustainable development goals
        • It will be important to distinguish small-scale perturbation experiments without climate relevance versus larger-scale testing that may be indistinguishable from deployment.
        • NASEM (2021) provides a proposed framework and approach for SRM research and governance, which emphasis engagement, input, and assessment. This includes exit ramps – “criteria and protocols for terminating research programs or areas” (NASEM 2021).
        • A report by the Climate Overshoot Commission (2023) calls for research on SRM and governance discussions as well as moratorium on SRM deployment and large-scale outdoor experiments.
        • UNESCO World Commission on the Ethics of Scientific Knowledge and Technology’s (COMEST) 2023 Report on the ethics of climate engineering has a slate of recommendations related to SRM covering governance, participation and inclusion, role of scientific knowledge and research strengthening capacity, and education, awareness, and advocacy.
        • In the absence of a governance framework there have been calls for governments to prohibit the development and deployment of SRM (Gupta et al. 2024). There is a need for governments to discuss coordination of research governance (Jinnah et al. 2024b).
        • An independent advisory committee for Harvard University’s Stratospheric Controlled Perturbation Experiment (SCoPEX) applied a research governance framework to the SCoPEx proposal detailed in the advisory committee’s final report (Jinnah et al. 2024a), which may inform future governance of outdoor experiments; this framework could potentially be applied to other atmospheric SRM approaches.
      • Specific to Sunshades:
        • There is currently no legal prohibition for climate intervention projects in space (Bodansky 1996). There are some frameworks that provide some guidance for space activities, but they are likely insufficient (Baum et al. 2022). These include:
        • The Outer Space Treaty of 1967 establishes outer space as “the province of all mankind” and establishes open access; any state is free to use space (Bodansky 1996, Baum et al. 2022)
          • Under this treaty, “the exploration and use of outer space … shall be carried out for the benefit and in the interests of all countries, irrespective of their degree of economic or scientific development”.
          • States are to avoid “adverse changes in the environment of the Earth” and are expected to consult with other states about whether an activity might have adverse effects (Bodansky 1996). However, there are no mechanisms for decision-making or resolving disputes (Bodansky 1996).
        • The UN Commission on Peaceful Uses of Outer Space, established by the UN General Assembly in 1959, aims for benefits of space technologies to apply to all countries (Baum et al. 2022).
        • The Environmental Modification Convention is a 1978 UN treaty that “prohibits military or hostile use of environmental modification techniques with widespread, long-lasting, or severe effects” (Baum et al. 2022).
        • See Goguichvili et al. (2021) for an overview on space governance (not specific to climate intervention).

• Distributive justice
  • Applicable to all approaches within Solar Radiation Modification:
    • Impacts from solar geoengineering have potential to cause disproportionate harm to those least responsible for climate change (DSG 2023). It is also possible that communities most exposed or vulnerable to climate hazards receive the most benefit, depending on the deployment. There is concern from vulnerable populations that research will overlook local needs and worsen global inequities (C2G 2021 Evidence Brief). There is an urgent need for justice-based recommendations (DSG 2023).
  • Specific to Sunshades:
    • Climate intervention in space would have global effects. Recent statements by United States officials claim that space is not a global commons or public good (Sutch and Roberts 2019). The assertion of individual states to rights to space and a race for dominion exacerbates unequal power relations and threatens distributive justice (Sutch and Roberts 2019). Hobe (2007) states that ideas of distributive justice included in Outer Space Treaty are not in practice. Claims about common interest in humanity and environment could be used in international law to reassert commons values in space and to challenge unilateralism (Sutch and Roberts 2019). Deplano (2023) proposes adoption of a proportionality test to guide benefit sharing under the Outer Space Treaty.
• Procedural justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If procedural justice is considered, people affected by research would have an opportunity to participate and have a say in how the approach will be researched, deployed, and governed. Because these approaches have global ramifications, procedural justice will be challenging (Preston 2013).
    • Efforts to support procedural justice for SRM in general to date have been inadequate (DSG 2023). Because of uncertainty in outcomes, variable interests, and the potential for wide-ranging effects, procedural justice is critical (DSG 2023).
    • Diversity within the SRM research community has generally been lacking (NASEM 2021). To address this, some organizations have supported participation in research for the Global South, but there has been a lack of attention on support for participation in governance (DSG 2023). Therefore, organizations and people may understand the science of an approach but not know how to translate their interests around the issue into policy, which is a significant justice gap (DSG 2023).
    • Bennett et al. (2022) suggests an inclusive governance approach that incorporates stakeholder concerns in the design and deployment of approaches and effectively communicates risk. Within the development of such a framework there is an opportunity to prioritize Indigenous self-determination and procedural justice (Chuffart et al. 2023). Note, however, that stakeholders may also include non-local people.
  • Specific to Sunshades:
    • No additional information
• Restorative justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If restorative justice is considered, plans would be developed for those who could be harmed by the approach to be compensated, rehabilitated, or restored (Preston 2013).
    • Horton and Keith (2019) proposed an international climate risk insurance pool where states supporting SRM deployment support the pool and opposing states would be insured against SRM risks.
  • Specific to Sunshades:
    • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There have been a series of open letters from academics and others that reject (Call for Non-Use Agreement) or support (Importance of Research on SRM, Call for Balance) solar radiation modification research, showing the current varying opinions that are shaping public perception.
  • The SCoPEx independent advisory committee offered four core principles for societal engagement related to solar radiation modification:
    • Start engagement efforts as early as possible
    • Include social scientists with engagement expertise on research teams during the research design process
    • Don’t presuppose what communities will be concerned about
    • Develop a plan to be responsive to community concern
  • A recent study on public perceptions found that people surveyed in the Global South were generally more supportive of research and development into SRM technologies compared to those from the Global North (Baum et al. 2024). Those from the Global South also expressed concern about unequal distribution of risks between rich and poor countries (Baum et al. 2024).
• Specific to Sunshades:
  • The public has not really been engaged in this topic (Baum et al. 2022).
  • No assessments of public perception, but one study conducted interviews with experts (Baum et al. 2022)
    • Among experts interviewed by Baum et al. (2022), space-based proposals have several advantages compared to other SRM techniques, such as:
      • not directly interfering with Earth’s biosphere
      • not needing to be redeployed every year (more likely every few decades)
    • The main concerns from experts interviewed by (Baum et al. 2022) included:
      • Concern that space geoengineering is too speculative, therefore resources would be better spent on other activities
      • The moral hazard argument, as space-based techniques do not address the cause of climate change
      • Concern that space-based methods won’t be ready for deployment when they would be needed.

• Applicable to all approaches within Solar Radiation Modification:
  • The principle of free, prior, and informed consent (FPIC) in the United Nations Declaration on the Rights of Indigenous Peoples (UNDRIP) is the foundation for engagement with Indigenous Peoples.
  • Particular to any potential Arctic research or deployment, The Inuit Circumpolar Council (2022) has published Circumpolar Inuit Protocols for Equitable and Ethical Engagement, which include eight protocols:
    • ‘Nothing About Us Without Us’ – Always Engage with Inuit
    • Recognize Indigenous Knowledge in its Own Right
    • Practice Good Governance
    • Communication with Intent
    • Exercising Accountability – Building Trust
    • Building Meaningful Partnerships
    • Information, Data Sharing, Ownership, and Permissions
    • Equitably Fund Inuit Representation and Knowledge
  • Any meaningful engagement with Indigenous peoples needs to consider context. Whyte (2018) states, “Indigenous voices should be involved in scientific and policy discussions of different types of geoengineering. But, context matters. Geoengineering discourses cannot just be associated with geoengineering to the exclusion of topics and solutions that Indigenous peoples value.”
• Specific to Sunshades:
  • Unknown
    • It is likely that Indigenous communities have not been engaged in this topic. Article 25 of the UN Declaration on the Rights of Indigenous Peoples (UNDRIP) protects Indigenous lands, specifically those traditionally occupied or used by Indigenous peoples, and does not directly protect any spiritual relationship of Indigenous peoples with outer space (Finnegan 2022). Finnegan (2022) calls for inclusion of Indigenous voices into conversations around international space plans and proposes several avenues.

• Applicable to all approaches within Solar Radiation Modification:
  • International regulations would likely need to be considered for all Solar Radiation Modification approaches as transboundary effects are likely, especially for larger field experiments and deployment, dependent on scale and area of application. Some research activities may fall under national jurisdiction.
• Specific to Sunshades:
  • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There is no formal governance framework for this approach (UNEP 2023). Governance efforts to date have been scattered and ad hoc (NASEM 2021). Governance is needed for at least two different levels: research and deployment (DSG).
    • The National Academy of Sciences’ (2021) report “Reflecting Sunlight: Recommendations for solar geoengineering research and research governance landscape” provides an overview of laws and international treaties that might apply to SRM. These include:
      • Domestic Law
        • US National Environmental Policy Act and state analogs
        • US Weather Modification Reporting Act and state analogs
        • Regulatory statutes
        • Tort Liability
        • Intellectual property law
      • International Environmental Law
        • Treaty Law
          • UN Convention on Biological Diversity
          • London Convention/London Protocol
          • UN Framework Convention on Climate Change
          • Vienna Convention and Montreal Protocol
          • Convention on Long-Range Transboundary Air Pollution (CLRTAP)
          • Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques (ENMOD)
          • UN Convention on the Law of the Sea
        • Customary International Law and Principles
          • Prevention of transboundary harm principle
          • Principle of intergenerational equity
          • The precautionary principle
          • Sustainable development goals
        • It will be important to distinguish small-scale perturbation experiments without climate relevance versus larger-scale testing that may be indistinguishable from deployment.
        • NASEM (2021) provides a proposed framework and approach for SRM research and governance, which emphasis engagement, input, and assessment. This includes exit ramps – “criteria and protocols for terminating research programs or areas” (NASEM 2021).
        • A report by the Climate Overshoot Commission (2023) calls for research on SRM and governance discussions as well as moratorium on SRM deployment and large-scale outdoor experiments.
        • UNESCO World Commission on the Ethics of Scientific Knowledge and Technology’s (COMEST) 2023 Report on the ethics of climate engineering has a slate of recommendations related to SRM covering governance, participation and inclusion, role of scientific knowledge and research strengthening capacity, and education, awareness, and advocacy.
        • In the absence of a governance framework there have been calls for governments to prohibit the development and deployment of SRM (Gupta et al. 2024). There is a need for governments to discuss coordination of research governance (Jinnah et al. 2024b).
        • An independent advisory committee for Harvard University’s Stratospheric Controlled Perturbation Experiment (SCoPEX) applied a research governance framework to the SCoPEx proposal detailed in the advisory committee’s final report (Jinnah et al. 2024a), which may inform future governance of outdoor experiments; this framework could potentially be applied to other atmospheric SRM approaches.
      • Specific to Sunshades:
        • There is currently no legal prohibition for climate intervention projects in space (Bodansky 1996). There are some frameworks that provide some guidance for space activities, but they are likely insufficient (Baum et al. 2022). These include:
        • The Outer Space Treaty of 1967 establishes outer space as “the province of all mankind” and establishes open access; any state is free to use space (Bodansky 1996, Baum et al. 2022)
          • Under this treaty, “the exploration and use of outer space … shall be carried out for the benefit and in the interests of all countries, irrespective of their degree of economic or scientific development”.
          • States are to avoid “adverse changes in the environment of the Earth” and are expected to consult with other states about whether an activity might have adverse effects (Bodansky 1996). However, there are no mechanisms for decision-making or resolving disputes (Bodansky 1996).
        • The UN Commission on Peaceful Uses of Outer Space, established by the UN General Assembly in 1959, aims for benefits of space technologies to apply to all countries (Baum et al. 2022).
        • The Environmental Modification Convention is a 1978 UN treaty that “prohibits military or hostile use of environmental modification techniques with widespread, long-lasting, or severe effects” (Baum et al. 2022).
        • See Goguichvili et al. (2021) for an overview on space governance (not specific to climate intervention).

• Distributive justice
  • Applicable to all approaches within Solar Radiation Modification:
    • Impacts from solar geoengineering have potential to cause disproportionate harm to those least responsible for climate change (DSG 2023). It is also possible that communities most exposed or vulnerable to climate hazards receive the most benefit, depending on the deployment. There is concern from vulnerable populations that research will overlook local needs and worsen global inequities (C2G 2021 Evidence Brief). There is an urgent need for justice-based recommendations (DSG 2023).
  • Specific to Sunshades:
    • Climate intervention in space would have global effects. Recent statements by United States officials claim that space is not a global commons or public good (Sutch and Roberts 2019). The assertion of individual states to rights to space and a race for dominion exacerbates unequal power relations and threatens distributive justice (Sutch and Roberts 2019). Hobe (2007) states that ideas of distributive justice included in Outer Space Treaty are not in practice. Claims about common interest in humanity and environment could be used in international law to reassert commons values in space and to challenge unilateralism (Sutch and Roberts 2019). Deplano (2023) proposes adoption of a proportionality test to guide benefit sharing under the Outer Space Treaty.
• Procedural justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If procedural justice is considered, people affected by research would have an opportunity to participate and have a say in how the approach will be researched, deployed, and governed. Because these approaches have global ramifications, procedural justice will be challenging (Preston 2013).
    • Efforts to support procedural justice for SRM in general to date have been inadequate (DSG 2023). Because of uncertainty in outcomes, variable interests, and the potential for wide-ranging effects, procedural justice is critical (DSG 2023).
    • Diversity within the SRM research community has generally been lacking (NASEM 2021). To address this, some organizations have supported participation in research for the Global South, but there has been a lack of attention on support for participation in governance (DSG 2023). Therefore, organizations and people may understand the science of an approach but not know how to translate their interests around the issue into policy, which is a significant justice gap (DSG 2023).
    • Bennett et al. (2022) suggests an inclusive governance approach that incorporates stakeholder concerns in the design and deployment of approaches and effectively communicates risk. Within the development of such a framework there is an opportunity to prioritize Indigenous self-determination and procedural justice (Chuffart et al. 2023). Note, however, that stakeholders may also include non-local people.
  • Specific to Sunshades:
    • No additional information
• Restorative justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If restorative justice is considered, plans would be developed for those who could be harmed by the approach to be compensated, rehabilitated, or restored (Preston 2013).
    • Horton and Keith (2019) proposed an international climate risk insurance pool where states supporting SRM deployment support the pool and opposing states would be insured against SRM risks.
  • Specific to Sunshades:
    • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There have been a series of open letters from academics and others that reject (Call for Non-Use Agreement) or support (Importance of Research on SRM, Call for Balance) solar radiation modification research, showing the current varying opinions that are shaping public perception.
  • The SCoPEx independent advisory committee offered four core principles for societal engagement related to solar radiation modification:
    • Start engagement efforts as early as possible
    • Include social scientists with engagement expertise on research teams during the research design process
    • Don’t presuppose what communities will be concerned about
    • Develop a plan to be responsive to community concern
  • A recent study on public perceptions found that people surveyed in the Global South were generally more supportive of research and development into SRM technologies compared to those from the Global North (Baum et al. 2024). Those from the Global South also expressed concern about unequal distribution of risks between rich and poor countries (Baum et al. 2024).
• Specific to Sunshades:
  • The public has not really been engaged in this topic (Baum et al. 2022).
  • No assessments of public perception, but one study conducted interviews with experts (Baum et al. 2022)
    • Among experts interviewed by Baum et al. (2022), space-based proposals have several advantages compared to other SRM techniques, such as:
      • not directly interfering with Earth’s biosphere
      • not needing to be redeployed every year (more likely every few decades)
    • The main concerns from experts interviewed by (Baum et al. 2022) included:
      • Concern that space geoengineering is too speculative, therefore resources would be better spent on other activities
      • The moral hazard argument, as space-based techniques do not address the cause of climate change
      • Concern that space-based methods won’t be ready for deployment when they would be needed.

• Applicable to all approaches within Solar Radiation Modification:
  • The principle of free, prior, and informed consent (FPIC) in the United Nations Declaration on the Rights of Indigenous Peoples (UNDRIP) is the foundation for engagement with Indigenous Peoples.
  • Particular to any potential Arctic research or deployment, The Inuit Circumpolar Council (2022) has published Circumpolar Inuit Protocols for Equitable and Ethical Engagement, which include eight protocols:
    • ‘Nothing About Us Without Us’ – Always Engage with Inuit
    • Recognize Indigenous Knowledge in its Own Right
    • Practice Good Governance
    • Communication with Intent
    • Exercising Accountability – Building Trust
    • Building Meaningful Partnerships
    • Information, Data Sharing, Ownership, and Permissions
    • Equitably Fund Inuit Representation and Knowledge
  • Any meaningful engagement with Indigenous peoples needs to consider context. Whyte (2018) states, “Indigenous voices should be involved in scientific and policy discussions of different types of geoengineering. But, context matters. Geoengineering discourses cannot just be associated with geoengineering to the exclusion of topics and solutions that Indigenous peoples value.”
• Specific to Sunshades:
  • Unknown
    • It is likely that Indigenous communities have not been engaged in this topic. Article 25 of the UN Declaration on the Rights of Indigenous Peoples (UNDRIP) protects Indigenous lands, specifically those traditionally occupied or used by Indigenous peoples, and does not directly protect any spiritual relationship of Indigenous peoples with outer space (Finnegan 2022). Finnegan (2022) calls for inclusion of Indigenous voices into conversations around international space plans and proposes several avenues.

• Applicable to all approaches within Solar Radiation Modification:
  • International regulations would likely need to be considered for all Solar Radiation Modification approaches as transboundary effects are likely, especially for larger field experiments and deployment, dependent on scale and area of application. Some research activities may fall under national jurisdiction.
• Specific to Sunshades:
  • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There is no formal governance framework for this approach (UNEP 2023). Governance efforts to date have been scattered and ad hoc (NASEM 2021). Governance is needed for at least two different levels: research and deployment (DSG).
    • The National Academy of Sciences’ (2021) report “Reflecting Sunlight: Recommendations for solar geoengineering research and research governance landscape” provides an overview of laws and international treaties that might apply to SRM. These include:
      • Domestic Law
        • US National Environmental Policy Act and state analogs
        • US Weather Modification Reporting Act and state analogs
        • Regulatory statutes
        • Tort Liability
        • Intellectual property law
      • International Environmental Law
        • Treaty Law
          • UN Convention on Biological Diversity
          • London Convention/London Protocol
          • UN Framework Convention on Climate Change
          • Vienna Convention and Montreal Protocol
          • Convention on Long-Range Transboundary Air Pollution (CLRTAP)
          • Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques (ENMOD)
          • UN Convention on the Law of the Sea
        • Customary International Law and Principles
          • Prevention of transboundary harm principle
          • Principle of intergenerational equity
          • The precautionary principle
          • Sustainable development goals
        • It will be important to distinguish small-scale perturbation experiments without climate relevance versus larger-scale testing that may be indistinguishable from deployment.
        • NASEM (2021) provides a proposed framework and approach for SRM research and governance, which emphasis engagement, input, and assessment. This includes exit ramps – “criteria and protocols for terminating research programs or areas” (NASEM 2021).
        • A report by the Climate Overshoot Commission (2023) calls for research on SRM and governance discussions as well as moratorium on SRM deployment and large-scale outdoor experiments.
        • UNESCO World Commission on the Ethics of Scientific Knowledge and Technology’s (COMEST) 2023 Report on the ethics of climate engineering has a slate of recommendations related to SRM covering governance, participation and inclusion, role of scientific knowledge and research strengthening capacity, and education, awareness, and advocacy.
        • In the absence of a governance framework there have been calls for governments to prohibit the development and deployment of SRM (Gupta et al. 2024). There is a need for governments to discuss coordination of research governance (Jinnah et al. 2024b).
        • An independent advisory committee for Harvard University’s Stratospheric Controlled Perturbation Experiment (SCoPEX) applied a research governance framework to the SCoPEx proposal detailed in the advisory committee’s final report (Jinnah et al. 2024a), which may inform future governance of outdoor experiments; this framework could potentially be applied to other atmospheric SRM approaches.
      • Specific to Sunshades:
        • There is currently no legal prohibition for climate intervention projects in space (Bodansky 1996). There are some frameworks that provide some guidance for space activities, but they are likely insufficient (Baum et al. 2022). These include:
        • The Outer Space Treaty of 1967 establishes outer space as “the province of all mankind” and establishes open access; any state is free to use space (Bodansky 1996, Baum et al. 2022)
          • Under this treaty, “the exploration and use of outer space … shall be carried out for the benefit and in the interests of all countries, irrespective of their degree of economic or scientific development”.
          • States are to avoid “adverse changes in the environment of the Earth” and are expected to consult with other states about whether an activity might have adverse effects (Bodansky 1996). However, there are no mechanisms for decision-making or resolving disputes (Bodansky 1996).
        • The UN Commission on Peaceful Uses of Outer Space, established by the UN General Assembly in 1959, aims for benefits of space technologies to apply to all countries (Baum et al. 2022).
        • The Environmental Modification Convention is a 1978 UN treaty that “prohibits military or hostile use of environmental modification techniques with widespread, long-lasting, or severe effects” (Baum et al. 2022).
        • See Goguichvili et al. (2021) for an overview on space governance (not specific to climate intervention).

• Here we define justice related to approaches to slow the loss of Arctic sea ice through distributive justice, procedural justice, and restorative justice. Following COMEST (2023), we consider questions of ethics through a justice lens.

• Distributive justice
  • Applicable to all approaches within Solar Radiation Modification:
    • Impacts from solar geoengineering have potential to cause disproportionate harm to those least responsible for climate change (DSG 2023). It is also possible that communities most exposed or vulnerable to climate hazards receive the most benefit, depending on the deployment. There is concern from vulnerable populations that research will overlook local needs and worsen global inequities (C2G 2021 Evidence Brief). There is an urgent need for justice-based recommendations (DSG 2023).
  • Specific to Sunshades:
    • Climate intervention in space would have global effects. Recent statements by United States officials claim that space is not a global commons or public good (Sutch and Roberts 2019). The assertion of individual states to rights to space and a race for dominion exacerbates unequal power relations and threatens distributive justice (Sutch and Roberts 2019). Hobe (2007) states that ideas of distributive justice included in Outer Space Treaty are not in practice. Claims about common interest in humanity and environment could be used in international law to reassert commons values in space and to challenge unilateralism (Sutch and Roberts 2019). Deplano (2023) proposes adoption of a proportionality test to guide benefit sharing under the Outer Space Treaty.
  • Procedural justice
    • Applicable to all approaches within Solar Radiation Modification:
      • If procedural justice is considered, people affected by research would have an opportunity to participate and have a say in how the approach will be researched, deployed, and governed. Because these approaches have global ramifications, procedural justice will be challenging (Preston 2013).
      • Efforts to support procedural justice for SRM in general to date have been inadequate (DSG 2023). Because of uncertainty in outcomes, variable interests, and the potential for wide-ranging effects, procedural justice is critical (DSG 2023).
      • Diversity within the SRM research community has generally been lacking (NASEM 2021). To address this, some organizations have supported participation in research for the Global South, but there has been a lack of attention on support for participation in governance (DSG 2023). Therefore, organizations and people may understand the science of an approach but not know how to translate their interests around the issue into policy, which is a significant justice gap (DSG 2023).
      • Bennett et al. (2022) suggests an inclusive governance approach that incorporates stakeholder concerns in the design and deployment of approaches and effectively communicates risk. Within the development of such a framework there is an opportunity to prioritize Indigenous self-determination and procedural justice (Chuffart et al. 2023). Note, however, that stakeholders may also include non-local people.
    • Specific to Sunshades:
      • No additional information
• Restorative justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If restorative justice is considered, plans would be developed for those who could be harmed by the approach to be compensated, rehabilitated, or restored (Preston 2013).
    • Horton and Keith (2019) proposed an international climate risk insurance pool where states supporting SRM deployment support the pool and opposing states would be insured against SRM risks.
  • Specific to Sunshades:
    • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There have been a series of open letters from academics and others that reject (Call for Non-Use Agreement) or support (Importance of Research on SRM, Call for Balance) solar radiation modification research, showing the current varying opinions that are shaping public perception.
  • The SCoPEx independent advisory committee offered four core principles for societal engagement related to solar radiation modification:
    • Start engagement efforts as early as possible
    • Include social scientists with engagement expertise on research teams during the research design process
    • Don’t presuppose what communities will be concerned about
    • Develop a plan to be responsive to community concern
  • A recent study on public perceptions found that people surveyed in the Global South were generally more supportive of research and development into SRM technologies compared to those from the Global North (Baum et al. 2024). Those from the Global South also expressed concern about unequal distribution of risks between rich and poor countries (Baum et al. 2024).
• Specific to Sunshades:
  • The public has not really been engaged in this topic (Baum et al. 2022).
  • No assessments of public perception, but one study conducted interviews with experts (Baum et al. 2022)
    • Among experts interviewed by Baum et al. (2022), space-based proposals have several advantages compared to other SRM techniques, such as:
      • not directly interfering with Earth’s biosphere
      • not needing to be redeployed every year (more likely every few decades)
    • The main concerns from experts interviewed by (Baum et al. 2022) included:
      • Concern that space geoengineering is too speculative, therefore resources would be better spent on other activities
      • The moral hazard argument, as space-based techniques do not address the cause of climate change
      • Concern that space-based methods won’t be ready for deployment when they would be needed.

• Applicable to all approaches within Solar Radiation Modification:
  • The principle of free, prior, and informed consent (FPIC) in the United Nations Declaration on the Rights of Indigenous Peoples (UNDRIP) is the foundation for engagement with Indigenous Peoples.
  • Particular to any potential Arctic research or deployment, The Inuit Circumpolar Council (2022) has published Circumpolar Inuit Protocols for Equitable and Ethical Engagement, which include eight protocols:
    • ‘Nothing About Us Without Us’ – Always Engage with Inuit
    • Recognize Indigenous Knowledge in its Own Right
    • Practice Good Governance
    • Communication with Intent
    • Exercising Accountability – Building Trust
    • Building Meaningful Partnerships
    • Information, Data Sharing, Ownership, and Permissions
    • Equitably Fund Inuit Representation and Knowledge
  • Any meaningful engagement with Indigenous peoples needs to consider context. Whyte (2018) states, “Indigenous voices should be involved in scientific and policy discussions of different types of geoengineering. But, context matters. Geoengineering discourses cannot just be associated with geoengineering to the exclusion of topics and solutions that Indigenous peoples value.”
• Specific to Sunshades:
  • Unknown
    • It is likely that Indigenous communities have not been engaged in this topic. Article 25 of the UN Declaration on the Rights of Indigenous Peoples (UNDRIP) protects Indigenous lands, specifically those traditionally occupied or used by Indigenous peoples, and does not directly protect any spiritual relationship of Indigenous peoples with outer space (Finnegan 2022). Finnegan (2022) calls for inclusion of Indigenous voices into conversations around international space plans and proposes several avenues.

• Applicable to all approaches within Solar Radiation Modification:
  • International regulations would likely need to be considered for all Solar Radiation Modification approaches as transboundary effects are likely, especially for larger field experiments and deployment, dependent on scale and area of application. Some research activities may fall under national jurisdiction.
• Specific to Sunshades:
  • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There is no formal governance framework for this approach (UNEP 2023). Governance efforts to date have been scattered and ad hoc (NASEM 2021). Governance is needed for at least two different levels: research and deployment (DSG).
    • The National Academy of Sciences’ (2021) report “Reflecting Sunlight: Recommendations for solar geoengineering research and research governance landscape” provides an overview of laws and international treaties that might apply to SRM. These include:
      • Domestic Law
        • US National Environmental Policy Act and state analogs
        • US Weather Modification Reporting Act and state analogs
        • Regulatory statutes
        • Tort Liability
        • Intellectual property law
      • International Environmental Law
        • Treaty Law
          • UN Convention on Biological Diversity
          • London Convention/London Protocol
          • UN Framework Convention on Climate Change
          • Vienna Convention and Montreal Protocol
          • Convention on Long-Range Transboundary Air Pollution (CLRTAP)
          • Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques (ENMOD)
          • UN Convention on the Law of the Sea
        • Customary International Law and Principles
          • Prevention of transboundary harm principle
          • Principle of intergenerational equity
          • The precautionary principle
          • Sustainable development goals
        • It will be important to distinguish small-scale perturbation experiments without climate relevance versus larger-scale testing that may be indistinguishable from deployment.
        • NASEM (2021) provides a proposed framework and approach for SRM research and governance, which emphasis engagement, input, and assessment. This includes exit ramps – “criteria and protocols for terminating research programs or areas” (NASEM 2021).
        • A report by the Climate Overshoot Commission (2023) calls for research on SRM and governance discussions as well as moratorium on SRM deployment and large-scale outdoor experiments.
        • UNESCO World Commission on the Ethics of Scientific Knowledge and Technology’s (COMEST) 2023 Report on the ethics of climate engineering has a slate of recommendations related to SRM covering governance, participation and inclusion, role of scientific knowledge and research strengthening capacity, and education, awareness, and advocacy.
        • In the absence of a governance framework there have been calls for governments to prohibit the development and deployment of SRM (Gupta et al. 2024). There is a need for governments to discuss coordination of research governance (Jinnah et al. 2024b).
        • An independent advisory committee for Harvard University’s Stratospheric Controlled Perturbation Experiment (SCoPEX) applied a research governance framework to the SCoPEx proposal detailed in the advisory committee’s final report (Jinnah et al. 2024a), which may inform future governance of outdoor experiments; this framework could potentially be applied to other atmospheric SRM approaches.
      • Specific to Sunshades:
        • There is currently no legal prohibition for climate intervention projects in space (Bodansky 1996). There are some frameworks that provide some guidance for space activities, but they are likely insufficient (Baum et al. 2022). These include:
        • The Outer Space Treaty of 1967 establishes outer space as “the province of all mankind” and establishes open access; any state is free to use space (Bodansky 1996, Baum et al. 2022)
          • Under this treaty, “the exploration and use of outer space … shall be carried out for the benefit and in the interests of all countries, irrespective of their degree of economic or scientific development”.
          • States are to avoid “adverse changes in the environment of the Earth” and are expected to consult with other states about whether an activity might have adverse effects (Bodansky 1996). However, there are no mechanisms for decision-making or resolving disputes (Bodansky 1996).
        • The UN Commission on Peaceful Uses of Outer Space, established by the UN General Assembly in 1959, aims for benefits of space technologies to apply to all countries (Baum et al. 2022).
        • The Environmental Modification Convention is a 1978 UN treaty that “prohibits military or hostile use of environmental modification techniques with widespread, long-lasting, or severe effects” (Baum et al. 2022).
        • See Goguichvili et al. (2021) for an overview on space governance (not specific to climate intervention).

• Here we define justice related to approaches to slow the loss of Arctic sea ice through distributive justice, procedural justice, and restorative justice. Following COMEST (2023), we consider questions of ethics through a justice lens.

• Distributive justice
  • Applicable to all approaches within Solar Radiation Modification:
    • Impacts from solar geoengineering have potential to cause disproportionate harm to those least responsible for climate change (DSG 2023). It is also possible that communities most exposed or vulnerable to climate hazards receive the most benefit, depending on the deployment. There is concern from vulnerable populations that research will overlook local needs and worsen global inequities (C2G 2021 Evidence Brief). There is an urgent need for justice-based recommendations (DSG 2023).
  • Specific to Sunshades:
    • Climate intervention in space would have global effects. Recent statements by United States officials claim that space is not a global commons or public good (Sutch and Roberts 2019). The assertion of individual states to rights to space and a race for dominion exacerbates unequal power relations and threatens distributive justice (Sutch and Roberts 2019). Hobe (2007) states that ideas of distributive justice included in Outer Space Treaty are not in practice. Claims about common interest in humanity and environment could be used in international law to reassert commons values in space and to challenge unilateralism (Sutch and Roberts 2019). Deplano (2023) proposes adoption of a proportionality test to guide benefit sharing under the Outer Space Treaty.
  • Procedural justice
    • Applicable to all approaches within Solar Radiation Modification:
      • If procedural justice is considered, people affected by research would have an opportunity to participate and have a say in how the approach will be researched, deployed, and governed. Because these approaches have global ramifications, procedural justice will be challenging (Preston 2013).
      • Efforts to support procedural justice for SRM in general to date have been inadequate (DSG 2023). Because of uncertainty in outcomes, variable interests, and the potential for wide-ranging effects, procedural justice is critical (DSG 2023).
      • Diversity within the SRM research community has generally been lacking (NASEM 2021). To address this, some organizations have supported participation in research for the Global South, but there has been a lack of attention on support for participation in governance (DSG 2023). Therefore, organizations and people may understand the science of an approach but not know how to translate their interests around the issue into policy, which is a significant justice gap (DSG 2023).
      • Bennett et al. (2022) suggests an inclusive governance approach that incorporates stakeholder concerns in the design and deployment of approaches and effectively communicates risk. Within the development of such a framework there is an opportunity to prioritize Indigenous self-determination and procedural justice (Chuffart et al. 2023). Note, however, that stakeholders may also include non-local people.
    • Specific to Sunshades:
      • No additional information
• Restorative justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If restorative justice is considered, plans would be developed for those who could be harmed by the approach to be compensated, rehabilitated, or restored (Preston 2013).
    • Horton and Keith (2019) proposed an international climate risk insurance pool where states supporting SRM deployment support the pool and opposing states would be insured against SRM risks.
  • Specific to Sunshades:
    • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There have been a series of open letters from academics and others that reject (Call for Non-Use Agreement) or support (Importance of Research on SRM, Call for Balance) solar radiation modification research, showing the current varying opinions that are shaping public perception.
  • The SCoPEx independent advisory committee offered four core principles for societal engagement related to solar radiation modification:
    • Start engagement efforts as early as possible
    • Include social scientists with engagement expertise on research teams during the research design process
    • Don’t presuppose what communities will be concerned about
    • Develop a plan to be responsive to community concern
  • A recent study on public perceptions found that people surveyed in the Global South were generally more supportive of research and development into SRM technologies compared to those from the Global North (Baum et al. 2024). Those from the Global South also expressed concern about unequal distribution of risks between rich and poor countries (Baum et al. 2024).
• Specific to Sunshades:
  • The public has not really been engaged in this topic (Baum et al. 2022).
  • No assessments of public perception, but one study conducted interviews with experts (Baum et al. 2022)
    • Among experts interviewed by Baum et al. (2022), space-based proposals have several advantages compared to other SRM techniques, such as:
      • not directly interfering with Earth’s biosphere
      • not needing to be redeployed every year (more likely every few decades)
    • The main concerns from experts interviewed by (Baum et al. 2022) included:
      • Concern that space geoengineering is too speculative, therefore resources would be better spent on other activities
      • The moral hazard argument, as space-based techniques do not address the cause of climate change
      • Concern that space-based methods won’t be ready for deployment when they would be needed.

• Applicable to all approaches within Solar Radiation Modification:
  • The principle of free, prior, and informed consent (FPIC) in the United Nations Declaration on the Rights of Indigenous Peoples (UNDRIP) is the foundation for engagement with Indigenous Peoples.
  • Particular to any potential Arctic research or deployment, The Inuit Circumpolar Council (2022) has published Circumpolar Inuit Protocols for Equitable and Ethical Engagement, which include eight protocols:
    • ‘Nothing About Us Without Us’ – Always Engage with Inuit
    • Recognize Indigenous Knowledge in its Own Right
    • Practice Good Governance
    • Communication with Intent
    • Exercising Accountability - Building Trust
    • Building Meaningful Partnerships
    • Information, Data Sharing, Ownership and Permissions
    • Equitably Fund Inuit Representation and Knowledge
  • Any meaningful engagement with Indigenous peoples needs to consider context. Whyte (2018) states, “Indigenous voices should be involved in scientific and policy discussions of different types of geoengineering. But, context matters. Geoengineering discourses cannot just be associated with geoengineering to the exclusion of topics and solutions that Indigenous peoples value.”
• Specific to Sunshades:
  • Unknown
    • It is likely that Indigenous communities have not been engaged in this topic. Article 25 of the UN Declaration on the Rights of Indigenous Peoples (UNDRIP) protects Indigenous lands, specifically those traditionally occupied or used by Indigenous peoples, and does not directly protect any spiritual relationship of Indigenous peoples with outer space (Finnegan 2022). Finnegan (2022) calls for inclusion of Indigenous voices into conversations around international space plans and proposes several avenues.

• Applicable to all approaches within Solar Radiation Modification:
  • International regulations would likely need to be considered for all Solar Radiation Modification approaches as transboundary effects are likely, especially for larger field experiments and deployment, dependent on scale and area of application. Some research activities may fall under national jurisdiction.
• Specific to Sunshades:
  • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There is no formal governance framework for this approach (UNEP 2023). Governance efforts to date have been scattered and ad hoc (NASEM 2021). Governance is needed for at least two different levels: research and deployment (DSG).
    • The National Academy of Sciences’ (2021) report “Reflecting Sunlight: Recommendations for solar geoengineering research and research governance landscape” provides an overview of laws and international treaties that might apply to SRM. These include:
      • Domestic Law
        • US National Environmental Policy Act and state analogs
        • US Weather Modification Reporting Act and state analogs
        • Regulatory statutes
        • Tort Liability
        • Intellectual property law
      • International Environmental Law
        • Treaty Law
          • UN Convention on Biological Diversity
          • London Convention/London Protocol
          • UN Framework Convention on Climate Change
          • Vienna Convention and Montreal Protocol
          • Convention on Long-Range Transboundary Air Pollution (CLRTAP)
          • Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques (ENMOD)
          • UN Convention on the Law of the Sea
        • Customary International Law and Principles
          • Prevention of transboundary harm principle
          • Principle of intergenerational equity
          • The precautionary principle
          • Sustainable development goals
        • It will be important to distinguish small-scale perturbation experiments without climate relevance versus larger-scale testing that may be indistinguishable from deployment.
        • NASEM (2021) provides a proposed framework and approach for SRM research and governance, which emphasis engagement, input, and assessment. This includes exit ramps – “criteria and protocols for terminating research programs or areas” (NASEM 2021).
        • A report by the Climate Overshoot Commission (2023) calls for research on SRM and governance discussions as well as moratorium on SRM deployment and large-scale outdoor experiments.
        • UNESCO World Commission on the Ethics of Scientific Knowledge and Technology’s (COMEST) 2023 Report on the ethics of climate engineering has a slate of recommendations related to SRM covering governance, participation and inclusion, role of scientific knowledge and research strengthening capacity, and education, awareness, and advocacy.
        • In the absence of a governance framework there have been calls for governments to prohibit the development and deployment of SRM (Gupta et al. 2024). There is a need for governments to discuss coordination of research governance (Jinnah et al. 2024b).
        • An independent advisory committee for Harvard University’s Stratospheric Controlled Perturbation Experiment (SCoPEX) applied a research governance framework to the SCoPEx proposal detailed in the advisory committee’s final report (Jinnah et al. 2024a), which may inform future governance of outdoor experiments; this framework could potentially be applied to other atmospheric SRM approaches.
      • Specific to Sunshades:
        • There is currently no legal prohibition for climate intervention projects in space (Bodansky 1996). There are some frameworks that provide some guidance for space activities, but they are likely insufficient (Baum et al. 2022). These include:
        • The Outer Space Treaty of 1967 establishes outer space as “the province of all mankind” and establishes open access; any state is free to use space (Bodansky 1996, Baum et al. 2022)
          • Under this treaty, “the exploration and use of outer space … shall be carried out for the benefit and in the interests of all countries, irrespective of their degree of economic or scientific development”.
          • States are to avoid “adverse changes in the environment of the Earth” and are expected to consult with other states about whether an activity might have adverse effects (Bodansky 1996). However, there are no mechanisms for decision-making or resolving disputes (Bodansky 1996).
        • The UN Commission on Peaceful Uses of Outer Space, established by the UN General Assembly in 1959, aims for benefits of space technologies to apply to all countries (Baum et al. 2022).
        • The Environmental Modification Convention is a 1978 UN treaty that “prohibits military or hostile use of environmental modification techniques with widespread, long-lasting, or severe effects” (Baum et al. 2022).
        • See Goguichvili et al. (2021) for an overview on space governance (not specific to climate intervention).

• Here we define justice related to approaches to slow the loss of Arctic sea ice through distributive justice, procedural justice, and restorative justice. Following COMEST (2023), we consider questions of ethics through a justice lens.

• Distributive justice
  • Applicable to all approaches within Solar Radiation Modification:
    • Impacts from solar geoengineering have potential to cause disproportionate harm to those least responsible for climate change (DSG 2023). It is also possible that communities most exposed or vulnerable to climate hazards receive the most benefit, depending on the deployment. There is concern from vulnerable populations that research will overlook local needs and worsen global inequities (C2G 2021 Evidence Brief). There is an urgent need for justice-based recommendations (DSG 2023).
  • Specific to Sunshades:
    • Climate intervention in space would have global effects. Recent statements by United States officials claim that space is not a global commons or public good (Sutch and Roberts 2019). The assertion of individual states to rights to space and a race for dominion exacerbates unequal power relations and threatens distributive justice (Sutch and Roberts 2019). Hobe (2007) states that ideas of distributive justice included in Outer Space Treaty are not in practice. Claims about common interest in humanity and environment could be used in international law to reassert commons values in space and to challenge unilateralism (Sutch and Roberts 2019). Deplano (2023) proposes adoption of a proportionality test to guide benefit sharing under the Outer Space Treaty.
  • Procedural justice
    • Applicable to all approaches within Solar Radiation Modification:
      • If procedural justice is considered, people affected by research would have an opportunity to participate and have a say in how the approach will be researched, deployed, and governed. Because these approaches have global ramifications, procedural justice will be challenging (Preston 2013).
      • Efforts to support procedural justice for SRM in general to date have been inadequate (DSG 2023). Because of uncertainty in outcomes, variable interests, and the potential for wide-ranging effects, procedural justice is critical (DSG 2023).
      • Diversity within the SRM research community has generally been lacking (NASEM 2021). To address this, some organizations have supported participation in research for the Global South, but there has been a lack of attention on support for participation in governance (DSG 2023). Therefore, organizations and people may understand the science of an approach but not know how to translate their interests around the issue into policy, which is a significant justice gap (DSG 2023).
      • Bennett et al. (2022) suggests an inclusive governance approach that incorporates stakeholder concerns in the design and deployment of approaches and effectively communicates risk. Within the development of such a framework there is an opportunity to prioritize Indigenous self-determination and procedural justice (Chuffart et al. 2023). Note, however, that stakeholders may also include non-local people.
    • Specific to Sunshades:
      • No additional information
• Restorative justice
  • Applicable to all approaches within Solar Radiation Modification:
    • If restorative justice is considered, plans would be developed for those who could be harmed by the approach to be compensated, rehabilitated, or restored (Preston 2013).
    • Horton and Keith (2019) proposed an international climate risk insurance pool where states supporting SRM deployment support the pool and opposing states would be insured against SRM risks.
  • Specific to Sunshades:
    • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There have been a series of open letters from academics and others that reject (Call for Non-Use Agreement) or support (Importance of Research on SRM, Call for Balance) solar radiation modification research, showing the current varying opinions that are shaping public perception.
  • The SCoPEx independent advisory committee offered four core principles for societal engagement related to solar radiation modification:
    • Start engagement efforts as early as possible
    • Include social scientists with engagement expertise on research teams during the research design process
    • Don’t presuppose what communities will be concerned about
    • Develop a plan to be responsive to community concern
  • A recent study on public perceptions found that people surveyed in the Global South were generally more supportive of research and development into SRM technologies compared to those from the Global North (Baum et al. 2024). Those from the Global South also expressed concern about unequal distribution of risks between rich and poor countries (Baum et al. 2024).
• Specific to Sunshades:
  • The public has not really been engaged in this topic (Baum et al. 2022).
  • No assessments of public perception, but one study conducted interviews with experts (Baum et al. 2022)
    • Among experts interviewed by Baum et al. (2022), space-based proposals have several advantages compared to other SRM techniques, such as:
      • not directly interfering with Earth’s biosphere
      • not needing to be redeployed every year (more likely every few decades)
    • The main concerns from experts interviewed by (Baum et al. 2022) included:
      • Concern that space geoengineering is too speculative, therefore resources would be better spent on other activities
      • The moral hazard argument, as space-based techniques do not address the cause of climate change
      • Concern that space-based methods won’t be ready for deployment when they would be needed.

• Applicable to all approaches within Solar Radiation Modification:
  • The principle of free, prior and informed consent (FPIC) in the United Nations Declaration on the Rights of Indigenous Peoples (UNDRIP) is the foundation for engagement with Indigenous Peoples.
  • Particular to any potential Arctic research or deployment, The Inuit Circumpolar Council (2022) has published Circumpolar Inuit Protocols for Equitable and Ethical Engagement, which include eight protocols:
    • ‘Nothing About Us Without Us’ – Always Engage with Inuit
    • Recognize Indigenous Knowledge in its Own Right
    • Practice Good Governance
    • Communication with Intent
    • Exercising Accountability - Building Trust
    • Building Meaningful Partnerships
    • Information, Data Sharing, Ownership and Permissions
    • Equitably Fund Inuit Representation and Knowledge
  • Any meaningful engagement with Indigenous peoples needs to consider context. Whyte (2018) states, “Indigenous voices should be involved in scientific and policy discussions of different types of geoengineering. But, context matters. Geoengineering discourses cannot just be associated with geoengineering to the exclusion of topics and solutions that Indigenous peoples value.”
• Specific to Sunshades:
  • Unknown
    • It is likely that Indigenous communities have not been engaged in this topic. Article 25 of the UN Declaration on the Rights of Indigenous Peoples (UNDRIP) protects Indigenous lands, specifically those traditionally occupied or used by Indigenous peoples, and does not directly protect any spiritual relationship of Indigenous peoples with outer space (Finnegan 2022). Finnegan (2022) calls for inclusion of Indigenous voices into conversations around international space plans and proposes several avenues.

• Applicable to all approaches within Solar Radiation Modification:
  • International regulations would likely need to be considered for all Solar Radiation Modification approaches as transboundary effects are likely, especially for larger field experiments and deployment, dependent on scale and area of application. Some research activities may fall under national jurisdiction.
• Specific to Sunshades:
  • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There is no formal governance framework for this approach (UNEP 2023). Governance efforts to date have been scattered and ad hoc (NASEM 2021). Governance is needed for at least two different levels: research and deployment (DSG).
    • The National Academy of Sciences’ (2021) report “Reflecting Sunlight: Recommendations for solar geoengineering research and research governance landscape” provides an overview of laws and international treaties that might apply to SRM. These include:
      • Domestic Law
        • US National Environmental Policy Act and state analogs
        • US Weather Modification Reporting Act and state analogs
        • Regulatory statutes
        • Tort Liability
        • Intellectual property law
      • International Environmental Law
        • Treaty Law
          • UN Convention on Biological Diversity
          • London Convention/London Protocol
          • UN Framework Convention on Climate Change
          • Vienna Convention and Montreal Protocol
          • Convention on Long-Range Transboundary Air Pollution (CLRTAP)
          • Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques (ENMOD)
          • UN Convention on the Law of the Sea
        • Customary International Law and Principles
          • Prevention of transboundary harm principle
          • Principle of intergenerational equity
          • The precautionary principle
          • Sustainable development goals
        • It will be important to distinguish small-scale perturbation experiments without climate relevance versus larger-scale testing that may be indistinguishable from deployment.
        • NASEM (2021) provides a proposed framework and approach for SRM research and governance, which emphasis engagement, input, and assessment. This includes exit ramps – “criteria and protocols for terminating research programs or areas” (NASEM 2021).
        • A report by the Climate Overshoot Commission (2023) calls for research on SRM and governance discussions as well as moratorium on SRM deployment and large-scale outdoor experiments.
        • UNESCO World Commission on the Ethics of Scientific Knowledge and Technology’s (COMEST) 2023 Report on the ethics of climate engineering has a slate of recommendations related to SRM covering governance, participation and inclusion, role of scientific knowledge and research strengthening capacity, and education, awareness, and advocacy.
        • In the absence of a governance framework there have been calls for governments to prohibit the development and deployment of SRM (Gupta et al. 2024). There is a need for governments to discuss coordination of research governance (Jinnah et al. 2024b).
        • An independent advisory committee for Harvard University’s Stratospheric Controlled Perturbation Experiment (SCoPEX) applied a research governance framework to the SCoPEx proposal detailed in the advisory committee’s final report (Jinnah et al. 2024a), which may inform future governance of outdoor experiments; this framework could potentially be applied to other atmospheric SRM approaches.
      • Specific to Sunshades:
        • There is currently no legal prohibition for climate intervention projects in space (Bodansky 1996). There are some frameworks that provide some guidance for space activities, but they are likely insufficient (Baum et al. 2022). These include:
        • The Outer Space Treaty of 1967 establishes outer space as “the province of all mankind” and establishes open access; any state is free to use space (Bodansky 1996, Baum et al. 2022)
          • Under this treaty, “the exploration and use of outer space … shall be carried out for the benefit and in the interests of all countries, irrespective of their degree of economic or scientific development”.
          • States are to avoid “adverse changes in the environment of the Earth” and are expected to consult with other states about whether an activity might have adverse effects (Bodansky 1996). However, there are no mechanisms for decision-making or resolving disputes (Bodansky 1996).
        • The UN Commission on Peaceful Uses of Outer Space, established by the UN General Assembly in 1959, aims for benefits of space technologies to apply to all countries (Baum et al. 2022).
        • The Environmental Modification Convention is a 1978 UN treaty that “prohibits military or hostile use of environmental modification techniques with widespread, long-lasting, or severe effects” (Baum et al. 2022).
        • See Goguichvili et al. (2021) for an overview on space governance (not specific to climate intervention).

• Here we define justice related to approaches to slow the loss of Arctic sea ice through distributive justice, procedural justice, and restorative justice. Following COMEST (2023), we consider questions of ethics through a justice lens.

• Distributive justice
  • Applicable to all approaches within Solar Radiation Modification:
    • Impacts from solar geoengineering have potential to cause disproportionate harm to those least responsible for climate change (DSG 2023). It is also possible that communities most exposed or vulnerable to climate hazards receive the most benefit, depending on the deployment. There is concern from vulnerable populations that research will overlook local needs and worsen global inequities (C2G 2021 Evidence Brief). There is an urgent need for justice-based recommendations (DSG 2023).
  • Specific to Sunshades:
    • Climate intervention in space would have global effects. Recent statements by United States officials claim that space is not a global commons or public good (Sutch and Roberts 2019). The assertion of individual states to rights to space and a race for dominion exacerbates unequal power relations and threatens distributive justice (Sutch and Roberts 2019). Hobe (2007) states that ideas of distributive justice included in Outer Space Treaty are not in practice. Claims about common interest in humanity and environment could be used in international law to reassert commons values in space and to challenge unilateralism (Sutch and Roberts 2019). Deplano (2023) proposes adoption of a proportionality test to guide benefit sharing under the Outer Space Treaty.
  • Procedural justice
    • Applicable to all approaches within Solar Radiation Modification:
      • If procedural justice is considered, people affected by research would have an opportunity to participate and have a say in how the approach will be researched, deployed, and governed. Because these approaches have global ramifications, procedural justice will be challenging (Preston 2013).
      • Efforts to support procedural justice for SRM in general to date have been inadequate (DSG 2023). Because of uncertainty in outcomes, variable interests, and the potential for wide-ranging effects, procedural justice is critical (DSG 2023).
      • Diversity within the SRM research community has generally been lacking (NASEM 2021). To address this, some organizations have supported participation in research for the Global South, but there has been a lack of attention on support for participation in governance (DSG 2023). Therefore, organizations and people may understand the science of an approach but not know how to translate their interests around the issue into policy, which is a significant justice gap (DSG 2023).
      • Bennett et al. (2022) suggests an inclusive governance approach that incorporates stakeholder concerns in the design and deployment of approaches and effectively communicates risk. Within the development of such a framework there is an opportunity to prioritize Indigenous self-determination and procedural justice (Chuffart et al. 2023). Note, however, that stakeholders may also include non-local people.
    • Specific to Sunshades:
      • No additional information
    • Restorative justice
      • Applicable to all approaches within Solar Radiation Modification:
        • If restorative justice is considered, plans would be developed for those who could be harmed by the approach to be compensated, rehabilitated, or restored (Preston 2013).
        • Horton and Keith (2019) proposed an international climate risk insurance pool where states supporting SRM deployment support the pool and opposing states would be insured against SRM risks.
      • Specific to Sunshades:
        • No additional information

• Applicable to all approaches within Solar Radiation Modification:
  • There have been a series of open letters from academics and others that reject (Call for Non-Use Agreement) or support (Importance of Research on SRM, Call for Balance) solar radiation modification research, showing the current varying opinions that are shaping public perception.
  • The SCoPEx independent advisory committee offered four core principles for societal engagement related to solar radiation modification:
    • Start engagement efforts as early as possible
    • Include social scientists with engagement expertise on research teams during the research design process
    • Don’t presuppose what communities will be concerned about
    • Develop a plan to be responsive to community concern
  • A recent study on public perceptions found that people surveyed in the Global South were generally more supportive of research and development into SRM technologies compared to those from the Global North (Baum et al. 2024). Those from the Global South also expressed concern about unequal distribution of risks between rich and poor countries (Baum et al. 2024).
• Specific to Sunshades:
  • The public has not really been engaged in this topic (Baum et al. 2022).
  • No assessments of public perception, but one study conducted interviews with experts (Baum et al. 2022)
    • Among experts interviewed by Baum et al. (2022), space-based proposals have several advantages compared to other SRM techniques, such as:
      • not directly interfering with Earth’s biosphere
      • not needing to be redeployed every year (more likely every few decades)
    • The main concerns from experts interviewed by (Baum et al. 2022) included:
      • Concern that space geoengineering is too speculative, therefore resources would be better spent on other activities
      • The moral hazard argument, as space-based techniques do not address the cause of climate change
      • Concern that space-based methods won’t be ready for deployment when they would be needed.

• Applicable to all approaches within Solar Radiation Modification:
  • The principle of free, prior and informed consent (FPIC) in the United Nations Declaration on the Rights of Indigenous Peoples (UNDRIP) is the foundation for engagement with Indigenous Peoples.
  • Particular to any potential Arctic research or deployment, The Inuit Circumpolar Council (2022) has published Circumpolar Inuit Protocols for Equitable and Ethical Engagement, which include eight protocols:
    • ‘Nothing About Us Without Us’ – Always Engage with Inuit
    • Recognize Indigenous Knowledge in its Own Right
    • Practice Good Governance
    • Communication with Intent
    • Exercising Accountability - Building Trust
    • Building Meaningful Partnerships
    • Information, Data Sharing, Ownership and Permissions
    • Equitably Fund Inuit Representation and Knowledge
  • Any meaningful engagement with Indigenous peoples needs to consider context. Whyte (2018) states, “Indigenous voices should be involved in scientific and policy discussions of different types of geoengineering. But, context matters. Geoengineering discourses cannot just be associated with geoengineering to the exclusion of topics and solutions that Indigenous peoples value.”
• Specific to Sunshades:
  • Unknown
    • It is likely that Indigenous communities have not been engaged in this topic. Article 25 of the UN Declaration on the Rights of Indigenous Peoples (UNDRIP) protects Indigenous lands, specifically those traditionally occupied or used by Indigenous peoples, and does not directly protect any spiritual relationship of Indigenous peoples with outer space (Finnegan 2022). Finnegan (2022) calls for inclusion of Indigenous voices into conversations around international space plans and proposes several avenues.