Knowledge Gaps
Physical science / mechanism
Version published:
September 5, 2024 - 1:16am
- Microphysical processes in the atmosphere – studies are suggested to use models and compare results to studies of volcanoes (NASEM 2021). However, dynamics within a volcanic plume (extreme temperatures, ash, other chemicals) may be very unrepresentative of aircraft injection, so there is also a need for other in-situ observations.
- Need agreement on what baseline data, relevant processes, and uncertainty estimations should be used for SAI studies (Russell et al. 2012, Irvine et al. 2016, NASEM 2021).
- NASEM (2021) detail open research questions related to the aerosol microphysics of SAI and the impact of SAI forcing on stratospheric and upper tropospheric composition. These questions can be addressed through a combination of laboratory measurements, modeling, observations, and potentially controlled experiments.
- Regional and Arctic impacts on climate (NASEM 2021)
- SRM simultaneously alters top of atmosphere (TOA) and surface radiation. Global cooling or warming is mostly based on TOA effects, but Arctic/regional effects will depend a lot on the surface forcing, including sea ice melting. How can we better estimate the impacts on sea ice?
- Microphysical processes in the atmosphere – studies are suggested to use models and compare results to studies of volcanoes (NASEM 2021). However, dynamics within a volcanic plume (extreme temperatures, ash, other chemicals) may be very unrepresentative of aircraft injection, so there is also a need for other in-situ observations.
- Need agreement on what baseline data, relevant processes, and uncertainty estimations should be used for SAI studies (Russell et al. 2012, Irvine et al. 2016, NASEM 2021).
- NASEM (2021) detail open research questions related to the aerosol microphysics of SAI and the impact of SAI forcing on stratospheric and upper tropospheric composition. These questions can be addressed through a combination of laboratory measurements, modeling, observations, and potentially controlled experiments.
- Regional and Arctic impacts on climate (NASEM 2021)
- SRM simultaneously alters top of atmosphere (TOA) and surface radiation. Global cooling or warming is mostly based on TOA effects, but Arctic/regional effects will depend a lot on the surface forcing, including sea ice melting. How can we better estimate the impacts on sea ice?
Engineering needs (technical feasibility)
Version published:
September 9, 2024 - 7:42pm
- Delivery mechanisms
- Higher altitudes increase efficiency and reduce amount of material needed, which might decrease some of the risks, however, it is not known how to get sufficient material to sufficient altitude, higher than 20 km (NASEM 2021). Challenges still exist to have appropriate aircraft to go to high altitudes (NASEM 2021); other options include rockets or ‘ballistic payloads’ from ground or balloons. Could result in more widely distributed deployment. See Smith et al. 2022a for discussion about possibilities for high altitude deployment. There is also a proposal to use soot to loft material (Gao et al. 2021).
- Subpolar deployment could be effective at cooling poles but would require developing a new fleet of aircraft (Smith et al. 2022b). Deployments at higher latitudes could use existing aircraft.
- Delivery of material by balloons could be cheaper than aircraft, but that technology is less developed (Irvine et al. 2016).
- Could deployments modeled with variable injection over space and time be achieved technically (Irvine et al. 2016)?
- Most work done on injection of SO2 gas, which is an aerosol precursor; alternate aerosols (SO4, H2SO4, and others) have been investigated less and there is more uncertainty (Irvine et al. 2016, NASEM 2021, see work by Sandro Vattioni).
- Delivery mechanisms
- Higher altitudes increase efficiency and reduce amount of material needed, which might decrease some of the risks, however, it is not known how to get sufficient material to sufficient altitude, higher than 20 km (NASEM 2021). Challenges still exist to have appropriate aircraft to go to high altitudes (NASEM 2021); other options include rockets or ‘ballistic payloads’ from ground or balloons. Could result in more widely distributed deployment. See Smith et al. 2022a for discussion about possibilities for high altitude deployment. There is also a proposal to use soot to loft material (Gao et al. 2021).
- Subpolar deployment could be effective at cooling poles but would require developing a new fleet of aircraft (Smith et al. 2022b). Deployments at higher latitudes could use existing aircraft.
- Delivery of material by balloons could be cheaper than aircraft, but that technology is less developed (Irvine et al. 2016).
- Could deployments modeled with variable injection over space and time be achieved technically (Irvine et al. 2016)?
- Most work done on injection of SO2 gas, which is an aerosol precursor; alternate aerosols (SO4, H2SO4, and others) have been investigated less and there is more uncertainty (Irvine et al. 2016, NASEM 2021, see work by Sandro Vattioni).
- Delivery mechanisms
- Higher altitudes increase efficiency and reduce amount of material needed, which might decrease some of the risks, however, it is not known how to get sufficient material to sufficient altitude, higher than 20 km (NASEM 2021). Challenges still exist to have appropriate aircraft to go to high altitudes (NASEM 2021); other options include rockets or ‘ballistic payloads’ from ground or balloons. Could result in more widely distributed deployment. See Smith et al. 2022a for discussion about possibilities for high altitude deployment. There is also a proposal to use soot to loft material (Gao et al. 2021).
- Subpolar deployment could be effective at cooling poles but would require developing a new fleet of aircraft (Smith et al. 2022b). Deployments at higher latitudes could use existing aircraft.
- Delivery of material by balloons could be cheaper than aircraft, but that technology is less developed (Irvine et al. 2016)
- Could deployments modeled with variable injection over space and time be achieved technically (Irvine et al. 2016)?
- Most work done on injection of SO2 gas, which is an aerosol precursor; alternate aerosols (SO4, H2SO4, and others) have been investigated less and there is more uncertainty (Irvine et al. 2016, NASEM 2021, see work by Sandro Vattioni).
Environmental risks / benefits
Version published:
September 13, 2024 - 7:09pm
- Atmosphere
- Effects of increased aerosols in the stratosphere on atmospheric chemistry and transport (NASEM 2021, WMO 2022).
- How do risks of SAI compare with risks of continued climate change with no intervention (Russell et al. 2012)?
- For both regional and global changes
- Should we be designing SAI for a different target rather than global temperature (e.g., preserving biomes and ecoregions, preserving cold winter temperatures in temperate and polar regions) and how should they be determined (Zarnetske et al. 2021)?
- UN Sustainable Development Goals (or other biodiversity goals) could inform targets.
- How would SAI impact biodiversity hotspots?
- What are the impacts of decoupling temperature increases from GHG concentrations on ecosystems? (e.g., cooler temperatures can either reduce or increase photosynthetic carbon uptake depending on species and conditions, nutrient limitation and drought can influence CO2 dynamics, continued acidification and impacted ability of ecosystems to uptake GHGs (Zarnetske et al. 2021).
- What are potential changes to the hydrological cycle? How will those changes impact ecosystems, particularly considering how ecosystems use water and impact hydrological and nutrient cycles (Zarnetske 2021)?
- Ocean impacts
- How does SAI impact ocean biogeochemistry (Zarnetske et al. 2021)?
- How do SRM methods alter important climate features in the ocean (e.g. location of intertropical convergence zone or oceanic upwelling) and how would this affect ecosystems and biodiversity?
- How do changes in freshwater input impact the ocean (acidification, circulation, biodiversity)?
- Some models report significant impacts to features like AMOC and upwelling, but they are not reproducible in other models. Further study of SAI impacts is needed (Duffey et al. 2023).
- It is difficult to attribute effects of SAI to deployment with the current state of climate science (C2G 2021 Evidence Brief).
- Atmosphere
- Effects of increased aerosols in the stratosphere on atmospheric chemistry and transport (NASEM 2021, WMO 2022).
- How do risks of SAI compare with risks of continued climate change with no intervention (Russell et al. 2012)?
- For both regional and global changes
- Should we be designing SAI for a different target rather than global temperature (e.g., preserving biomes and ecoregions, preserving cold winter temperatures in temperate and polar regions) and how should they be determined (Zarnetske et al. 2021)?
- UN Sustainable Development Goals (or other biodiversity goals) could inform targets.
- How would SAI impact biodiversity hotspots?
- What are the impacts of decoupling temperature increases from GHG concentrations on ecosystems? (e.g., cooler temperatures can either reduce or increase photosynthetic carbon uptake depending on species and conditions, nutrient limitation and drought can influence CO2 dynamics, continued acidification and impacted ability of ecosystems to uptake GHGs (Zarnetske et al. 2021).
- What are potential changes to the hydrological cycle? How will those changes impact ecosystems, particularly considering how ecosystems use water and impact hydrological and nutrient cycles (Zarnetske 2021)?
- Ocean impacts
- How does SAI impact ocean biogeochemistry (Zarnetske et al. 2021)?
- How do SRM methods alter important climate features in the ocean (e.g. location of intertropical convergence zone or oceanic upwelling) and how would this affect ecosystems and biodiversity?
- How do changes in freshwater input impact the ocean (acidification, circulation, biodiversity)?
- Some models report significant impacts to features like AMOC and upwelling, but they are not reproducible in other models. Further study of SAI impacts is needed (Duffey et al. 2023).
- It is difficult to attribute effects of SAI to deployment with the current state of climate science (C2G 2021 Evidence Brief).
- Atmosphere
- Effects of increased aerosols in the stratosphere on atmospheric chemistry and transport (NASEM 2021, WMO 2022)
- How do risks of SAI compare with risks of continued climate change with no intervention? (Russell et al. 2012)
- For both regional and global changes
- Should we be designing SAI for a different target rather than global temperature (e.g., preserving biomes and ecoregions, preserving cold winter temperatures in temperate and polar regions) and how should they be determined? (Zarnetske et al. 2021)
- UN Sustainable Development Goals (or other biodiversity goals) could inform targets
- How would SAI impact biodiversity hotspots?
- What are the impacts of decoupling temperature increases from GHG concentrations on ecosystems? (e.g., cooler temperatures can either reduce or increase photosynthetic carbon uptake depending on species and conditions, nutrient limitation and drought can influence CO2 dynamics, continued acidification and impacted ability of ecosystems to uptake GHGs (Zarnetske et al. 2021).
- What are potential changes to the hydrological cycle? How will those changes impact ecosystems, particularly considering how ecosystems use water and impact hydrological and nutrient cycles (Zarnetske 2021)?
- Ocean impacts
- How does SAI impact ocean biogeochemistry (Zarnetske et al. 2021)?
- How do SRM methods alter important climate features in the ocean (e.g. location of intertropical convergence zone or oceanic upwelling) and how would this affect ecosystems and biodiversity?
- How do changes in freshwater input impact the ocean (acidification, circulation, biodiversity)?
- Some models report significant impacts to features like AMOC and upwelling, but they are not reproducible in other models. Further study of SAI impacts is needed (Duffey et al. 2023).
- It is difficult to attribute effects of SAI to deployment with the current state of climate science (C2G 2021 Evidence Brief).
- Atmosphere
- Effects of increased aerosols in the stratosphere on atmospheric chemistry and transport (NASEM 2021, WMO 2022)
- How do risks of SAI compare with risks of continued climate change with no intervention? (Russell et al. 2012)
- For both regional and global changes
- Should we be designing SAI for a different target rather than global temperature (e.g., preserving biomes and ecoregions, preserving cold winter temperatures in temperate and polar regions) and how should they be determined? (Zarnetske et al. 2021)
- UN Sustainable Development Goals (or other biodiversity goals) could inform targets
- How would SAI impact biodiversity hotspots?
- What are the impacts of decoupling temperature increases from GHG concentrations on ecosystems? (e.g., cooler temperatures can either reduce or increase photosynthetic carbon uptake depending on species and conditions, nutrient limitation and drought can influence CO2 dynamics, continued acidification and impacted ability of ecosystems to uptake GHGs (Zarnetske et al. 2021).
- What are potential changes to the hydrological cycle? How will those changes impact ecosystems, particularly considering how ecosystems use water and impact hydrological and nutrient cycles (Zarnetske 2021)?
- Ocean impacts
- How does SAI impact ocean biogeochemistry (Zarnetske et al. 2021)?
- How do SRM methods alter important climate features in the ocean (e.g. location of intertropical convergence zone or oceanic upwelling) and how would this affect ecosystems and biodiversity?
- How do changes in freshwater input impact the ocean (acidification, circulation, biodiversity)?
- Some models report significant impacts to features like AMOC and upwelling, but they are not reproducible in other models. Further study of SAI impacts is needed (Duffey et al. 2023).
- It is difficult to attribute effects of SAI to deployment with the current state of climate science (C2G 2021 Evidence Brief).
- Atmosphere
- Effects of increased aerosols in the stratosphere on atmospheric chemistry and transport (NASEM 2021, WMO 2022)
- How do risks of SAI compare with risks of continued climate change with no intervention? (Russell et al. 2012)
- For both regional and global changes
- Should we be designing SAI for a different target rather than global temperature (e.g., preserving biomes and ecoregions, preserving cold winter temperatures in temperate and polar regions) and how should they be determined? (Zarnetske et al. 2021)
- UN Sustainable Development Goals (or other biodiversity goals) could inform targets
- How would SAI impact biodiversity hotspots?
- What are the impacts of decoupling temperature increases from GHG concentrations on ecosystems? (e.g., cooler temperatures can either reduce or increase photosynthetic carbon uptake depending on species and conditions, nutrient limitation and drought can influence CO2 dynamics, continued acidification and impacted ability of ecosystems to uptake GHGs (Zarnetske et al. 2021).
- What are potential changes to the hydrological cycle? How will those changes impact ecosystems, particularly considering how ecosystems use water and impact hydrological and nutrient cycles (Zarnetske 2021)?
- Ocean impacts
- How does SAI impact ocean biogeochemistry? (Zarnetske et al. 2021)
- How do SRM methods alter key components of the climate system (e.g. location of intertropical convergence zone or oceanic upwelling) and how would this affect ecosystems and biodiversity? (
- Need to see how SAI would impact certain important climate features in the ocean
- How do changes in freshwater input impact the ocean (acidification, circulation, biodiversity)?
- Some models report significant impacts to features like AMOC and upwelling, but they are not reproducible in other models. Further study of SAI impacts is needed. (Duffey et al. 2023)
- It is difficult to attribute effects of SAI to deployment with the current state of climate science (C2G 2021 Evidence Brief)
- Atmosphere
- Effects of increased aerosols in the stratosphere on atmospheric chemistry and transport (NASEM 2021, WMO 2022)
- How do risks of SAI compare with risks of continued climate change with no intervention? (Russell et al. 2012)
- For both regional and global changes
- Should we be designing SAI for a different target rather than global temperature (e.g., preserving biomes and ecoregions, preserving cold winter temperatures in temperate and polar regions) and how should they be determined? (Zarnetske et al. 2021)
- UN Sustainable Development Goals (or other biodiversity goals) could inform targets
- How would SAI impact biodiversity hotspots?
- What are the impacts of decoupling temperature increases from GHG concentrations on ecosystems: e.g., cooler temperatures can either reduce or increase photosynthetic carbon uptake depending on species and conditions, nutrient limitation and drought can influence CO2 dynamics, continued acidification and impacted ability of ecosystems to uptake GHGs (Zarnetske et al. 2021)
- Changes in the hydrological cycle and how that impacts ecosystems and how ecosystems use water and impact hydrological and nutrient cycles (Zarnetske 2021)
- Ocean impacts
- How does SAI impact ocean biogeochemistry? (Zarnetske et al. 2021)
- How do SRM methods alter key components of the climate system (e.g. location of intertropical convergence zone or oceanic upwelling) and how would this affect ecosystems and biodiversity? (
- Need to see how SAI would impact certain important climate features in the ocean
- How do changes in freshwater input impact the ocean (acidification, circulation, biodiversity)?
- Some models report significant impacts to features like AMOC and upwelling, but they are not reproducible in other models. Further study of SAI impacts is needed. (Duffey et al. 2023)
- It is difficult to attribute effects of SAI to deployment with the current state of climate science (C2G 2021 Evidence Brief)
- Atmosphere
- Effects of increased aerosols in the stratosphere on atmospheric chemistry and transport (NASEM 2021, WMO 2022)
- How do risks of SAI compare with risks of continued climate change with no intervention? (Russell et al. 2012)
- For both regional and global changes
- Should we be designing SAI for a different target rather than global temperature (e.g., preserving biomes and ecoregions, preserving cold winter temperatures in temperate and polar regions) and how should they be determined? (Zarnetske et al. 2021)
- UN Sustainable Development Goals (or other biodiversity goals) could inform targets
- How would SAI impact biodiversity hotspots?
- What are the impacts of decoupling temperature increases from GHG concentrations on ecosystems: e.g., cooler temperatures can either reduce or increase photosynthetic carbon uptake depending on species and conditions, nutrient limitation and drought can influence CO2 dynamics, continued acidification and impacted ability of ecosystems to uptake GHGs (Zarnetske et al. 2021)
- Changes in the hydrological cycle and how that impacts ecosystems and how ecosystems use water and impact hydrological and nutrient cycles (Zarnetske 2021)
- Ocean impacts
- How does SAI impact ocean biogeochemistry? (Zarnetske et al. 2021)
- How do SRM methods alter key components of the climate system (e.g. location of intertropical convergence zone or oceanic upwelling) and how would this affect ecosystems and biodiversity? (
- Need to see how SAI would impact certain important climate features in the ocean
- How do changes in freshwater input impact the ocean (acidification, circulation, biodiversity)?
- Some models report significant impacts to features like AMOC and upwelling, but they are not reproducible in other models. Further study of SAI impacts is needed. (Duffey et al. 2023)
- It is difficult to attribute effects of SAI to deployment with the current state of climate science (C2G 2021 Evidence Brief)
Governance
Version published:
September 13, 2024 - 7:09pm
- Who would decide to deploy SRM (C2G 2021 Evidence Brief)?
- How much cooling might be appropriate (C2G 2021 Evidence Brief)?
- How would liability for (perceived) damages be dealt with and how might ‘losers’ be compensated (C2G 2021 Evidence Brief)?
- Can Indigenous rights and perspectives be incorporated in governance of climate solutions when solutions are implemented in the name of global environmental protection (Chuffart et al. 2023)?
- Who would decide to deploy SRM (C2G 2021 Evidence Brief)?
- How much cooling might be appropriate (C2G 2021 Evidence Brief)?
- How would liability for (perceived) damages be dealt with and how might ‘losers’ be compensated (C2G 2021 Evidence Brief)?
- Can Indigenous rights and perspectives be incorporated in governance of climate solutions when solutions are implemented in the name of global environmental protection (Chuffart et al. 2023)?
- Who would decide to deploy SRM? (C2G 2021 Evidence Brief)
- How much cooling might be appropriate? (C2G 2021 Evidence Brief)
- How would liability for (perceived) damages be dealt with and how might ‘losers’ be compensated? (C2G 2021 Evidence Brief)
- Can Indigenous rights and perspectives be incorporated in governance of climate solutions when solutions are implemented in the name of global environmental protection? (Chuffart et al. 2023)
- Who would decide to deploy SRM? (C2G 2021 Evidence Brief)
- How much cooling might be appropriate? (C2G 2021 Evidence Brief)
- How would liability for (perceived) damages be dealt with and how might ‘losers’ be compensated? (C2G 2021 Evidence Brief)
- Can Indigenous rights and perspectives be incorporated in governance of climate solutions when solutions are implemented in the name of global environmental protection? (Chuffart et al. 2023)
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