Knowledge Gaps
Physical science / mechanism
Version published:
May 15, 2025 - 12:32pm
- Atmosphere-ocean interactions
- Regional impacts
- What baseline data should be used (Russell et al. 2012)?
- Cloud microphysical knowledge gaps (Feingold et al. 2022)
- Small-scale cloud processes are currently not well understood, and they are not easy to observe/measure/quantify.
- Aerosol emissions cause changes to cloud amount through changes in precipitation and evaporation and are known to sometimes enhance and sometimes offset cloud brightening. Improved understanding of these offsets and their prevalence is essential.
- The efficiency with which aerosol particles can be delivered into clouds to enhance cloud drop number concentrations is uncertain.
- More data is needed to determine what portion of released sea salt particles are incorporated into clouds, and modeling studies need to consider processes involved in the dispersion of the sea salt aerosol plume (Hernandez-Jaramillo et al. 2025).
- The optimal aerosol composition, size, and concentration for attaining the desired cloud response is unknown (Feingold et al. 2022).
- Meteorological-aerosol co-variability knowledge gaps (Feingold et al. 2022).
- There is a need to identify and quantify the frequency of occurrence of regions that are highly susceptible to aerosol injections – typically environments supporting thin, layered clouds with low background aerosol concentrations – and to determine whether Arctic responses scale up well enough for a significant regional and global radiative effect.
- Large-scale knowledge gaps (Feingold et al. 2022)
- There is a lack of adequate tools to assess how small-scale perturbations to cloud brightness might affect larger-scale circulations, and the extent to which these might contribute to regional changes in precipitation and radiative forcing of the climate. Furthermore, the timescales of these feedbacks are poorly quantified.
- Detection-related knowledge gaps (Feingold et al. 2022)
- Given the relatively small aerosol-cloud brightening signals, there is a need to assess how long it would take to detect MCB-related brightening against the background of meteorological variability, and to ascertain whether detection times are short enough for strategies to be changed in response to changing conditions.
- The adequacy of current and planned future space-based detection systems needs to be determined.
- Need larger-scale field experiments to understand real-world plume behavior and cloud responses and to validate models (Hernandez-Jaramillo et al. 2025).
- Insufficient evaluation of impacts of mixed climate intervention scenarios and strategies, e.g. SAI and MCB (Haywood et al. 2025).
- Need to determine interactions among SRM, mitigation (e.g. renewable energy), and CDR (Haywood et al. 2025).
Engineering needs (technical feasibility)
Version published:
May 15, 2025 - 12:32pm
- Need to develop a spraying system/nozzle capable of producing seawater aerosol at the appropriate size distribution (Latham et al. 2012).
- Nozzle design and generation of particles of desired size distribution (Feingold et al. 2022).
- Delivery system would need to be able to perform for long periods of time at sea and overcome challenges from clogging and adverse weather (Latham et al. 2012).
- It’s still unknown if the delivery could be done at a large enough area to impact cloud albedo on a scale sufficient to produce cooling (Latham et al. 2012).
Environmental risks / benefits
Version published:
May 15, 2025 - 12:32pm
- More research on ecosystem impacts is needed (Russell et al. 2012, Hernandez-Jaramillo et al. 2025). This should involve collaboration with the marine biology/ecology community (Haywood et al. 2025).
- How do risks compare with risks of continued climate change with no intervention (Russell et al. 2012)?
- Determine how MCB would impact certain important climate features in the ocean, such as the location of the intertropical convergence zone and oceanic upwelling systems, and subsequent impacts on marine ecosystems and biodiversity (Russell et al. 2012).
- How do changes in freshwater input impact the ocean (acidification, circulation, biodiversity)?
- How might MCB affect regional fisheries production (Haywood et al. 2025)?
- Should we be designing MCB 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:
May 15, 2025 - 12:32pm
- 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)?
- Policy and governance frameworks need to be developed for this approach (Hernandez-Jaramillo et al. 2025).
- 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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