Knowledge Gaps
Physical science / mechanism
Version published: 
September 13, 2024 - 7:26pm
- For the variety of altitudes and thicknesses of MPCs, the maximum and effective amount of cooling possible from glaciation is variable and not quantified.
- Feedbacks of MPCs on cloud liquid water path are not known and require quantification to quantify the duration of cooling.
- Ice nucleation in clouds is highly uncertain both for primary ice nucleation (ice that forms on dust and other ice nucleating particles) and for secondary ice nucleation (ice particles that shed small fragments of ice due to various processes like collisions with other crystals and water droplets).
- Effective distribution of INP or dry ice to susceptible clouds requires careful planning and optimization in light of MPC distribution patterns.
- Model outputs are highly uncertain because MPCs are less understood compared to warm clouds (Villanueva et al. 2022). Therefore, more knowledge is needed about MPCs in general to have higher confidence in models.
- Models cannot resolve the various microscale processes that determine the response of MPCs to seeding. This is also a problem for model predictions of aerosol effects on warm clouds, and that challenge is multiplied for MPCs because of the tremendous complexity of also having the ice phase.
- The potential impacts on hydrological cycle and precipitation need further study (Villanueva et al. 2022).
- The effects of cloud seeding and MPCT on sea ice surface area need further study (Zapalac 2023).
- Field experiments in a relevant range of seasonal and geographically diverse conditions are needed to evaluate MPCT and for comparison to model simulations (Zapalac 2023). Experiments need to be able to measure relevant parameters in perturbed and unperturbed conditions for 12-48 hr.
- Observational studies are needed to determine the cooling from MPCT separately from model simulations. This could be from dedicated field experiments as well as from analyzing the variability in MPCs and how that is linked to naturally occurring variability in aerosols.
- For the variety of altitudes and thicknesses of MPCs, the maximum and effective amount of cooling possible from glaciation is variable and not quantified.
- Feedbacks of MPCs on cloud liquid water path are not known and require quantification to quantify the duration of cooling.
- Ice nucleation in clouds is highly uncertain both for primary ice nucleation (ice that forms on dust and other ice nucleating particles) and for secondary ice nucleation (ice particles that shed small fragments of ice due to various processes like collisions with other crystals and water droplets).
- Effective distribution of INP or dry ice to susceptible clouds requires careful planning and optimization in light of MPC distribution patterns.
- Model outputs are highly uncertain because MPCs are less understood compared to warm clouds (Villanueva et al. 2022). Therefore, more knowledge is needed about MPCs in general to have higher confidence in models.
- Models cannot resolve the various microscale processes that determine the response of MPCs to seeding. This is also a problem for model predictions of aerosol effects on warm clouds, and that challenge is multiplied for MPCs because of the tremendous complexity of also having the ice phase.
- The potential impacts on hydrological cycle and precipitation need further study (Villanueva et al. 2022).
- The effects of cloud seeding and MPCT on sea ice surface area need further study (Zapalac 2023).
- Field experiments in a relevant range of seasonal and geographically diverse conditions are needed to evaluate MPCT and for comparison to model simulations (Zapalac 2023). Experiments need to be able to measure relevant parameters in perturbed and unperturbed conditions for 12-48 hr.
- Observational studies are needed to determine the cooling from MPCT separately from model simulations. This could be from dedicated field experiments as well as from analyzing the variability in MPCs and how that is linked to naturally occurring variability in aerosols.
- For the variety of altitudes and thicknesses of MPCs, the maximum and effective amount of cooling possible from glaciation is variable and not quantified.
- Feedbacks of MPCs on cloud liquid water path are not known and require quantification to quantify the duration of cooling.
- Ice nucleation in clouds is highly uncertain both for primary ice nucleation (ice that forms on dust and other ice nucleating particles) and for secondary ice nucleation (ice particles that shed small fragments of ice due to various processes like collisions with other crystals and water droplets)
- Effective distribution of INP or dry ice to susceptible clouds requires careful planning and optimization in light of MPC distribution patterns.
- Model outputs are highly uncertain because MPCs are less understood compared to warm clouds (Villanueva et al. 2022). Therefore, more knowledge is needed about MPCs in general to have higher confidence in models.
- Models cannot resolve the various microscale processes that determine the response of MPCs to seeding. This is also a problem for model predictions of aerosol effects on warm clouds, and that challenge is multiplied for MPCs because of the tremendous complexity of also having the ice phase.
- The potential impacts on hydrological cycle and precipitation need further study (Villanueva et al. 2022).
- The effects of cloud seeding and MPCT on sea ice surface area need further study (Zapalac 2023).
- Field experiments in a relevant range of seasonal and geographically diverse conditions are needed to evaluate MPCT and for comparison to model simulations (Zapalac 2023). Experiments need to be able to measure relevant parameters in perturbed and unperturbed conditions for 12-48 hr.
- Observational studies are needed to determine the cooling from MPCT separately from model simulations. This could be from dedicated field experiments as well as from analyzing the variability in MPCs and how that is linked to naturally occurring variability in aerosols.
Engineering needs (technical feasibility)
Version published: 
September 9, 2024 - 4:33pm
- Need to do field experiments and further study to determine appropriate frequency for re-seeding clouds (Zapalac 2023).
- Further study of potential INPs.
- How would materials used for an Arctic deployment impact Arctic ecosystems, especially INPs?
- Need to do field experiments and further study to determine appropriate frequency for re-seeding clouds (Zapalac 2023).
- Further study of potential INPs.
- How would materials used for an Arctic deployment impact Arctic ecosystems, especially INPs?
- Need to do field experiments and further study to determine appropriate frequency for re-seeding clouds (Zapalac 2023)
- Further study of potential INPs
- How would materials used for an Arctic deployment impact Arctic ecosystems, especially INPs?
Scalability
Version published: 
September 4, 2024 - 11:21pm
- Would only work in winter so would likely need another strategy to prevent sea ice melting in summer, although thicker sea ice should take longer to melt. Need exploration of what options might be complementary.
- Would only work in winter so would likely need another strategy to prevent sea ice melting in summer, although thicker sea ice should take longer to melt. Need exploration of what options might be complementary.
Environmental risks / benefits
Version published: 
September 13, 2024 - 7:26pm
- Need to assess impact on ecosystem (Villanueva et al. 2022), especially for the Arctic.
- Should we be designing MPCT for a different target rather than global temperature (e.g., preserving biomes and ecoregions, preserving cold winter temperatures in temperate and polar regions)? See Zarnetske et al. (2021) for the same question raised about stratospheric aerosol injection.
- UN Sustainable Development Goals (or other biodiversity goals) could inform targets.
- Need to assess impact on ecosystem (Villanueva et al. 2022), especially for the Arctic.
- Should we be designing MPCT for a different target rather than global temperature (e.g., preserving biomes and ecoregions, preserving cold winter temperatures in temperate and polar regions)? See Zarnetske et al. (2021) for the same question raised about stratospheric aerosol injection.
- UN Sustainable Development Goals (or other biodiversity goals) could inform targets.
- Need to assess impact on ecosystem (Villanueva et al. 2022), especially for the Arctic.
- Should we be designing MPCT for a different target rather than global temperature (e.g., preserving biomes and ecoregions, preserving cold winter temperatures in temperate and polar regions)? See Zarnetske et al. (2021) for the same question raised about stratospheric aerosol injection.
- UN Sustainable Development Goals (or other biodiversity goals) could inform targets
Governance
Version published: 
September 13, 2024 - 7:28pm
- Need research to identify viable structure for implementation.
- 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)?
- Need research to identify viable structure for implementation.
- 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)?
- Need research to identify viable structure for implementation.
- 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)
- Need research to identify viable structure for implementation.
- 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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