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Solar Radiation Management

Last updated in October 2024.


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Executive summary

  • What is solar radiation management (SRM)? Solar radiation management (SRM) encompasses a range of techniques aimed at reflecting sunlight to reduce global temperatures. The most studied and acknowledged for its potential to achieve global cooling is Stratospheric Aerosol Injection (SAI).

  • How could stratospheric aerosol injection (SAI) temporarily reduce radiative forcing? SAI is not a trade-off to climate mitigation, nor does it address the root causes of climate change, i.e., increasing greenhouse gas emissions. SAI could act as a temporary measure to reduce radiative forcing by injecting reflective aerosols into the stratosphere to increase Earth's albedo. This method reflects a portion of incoming solar radiation back into space, thereby reducing the amount of energy absorbed by the Earth. The cooling effect achieved through SAI would be temporary, as the aerosols typically remain in the stratosphere for one to three years, requiring continual injections to maintain the effect.

  • What are the potential co-benefits and risks of SRM? We recognize the significant uncertainties surrounding SRM and believe it should only be considered in extreme circumstances due to its potential risks. We do not know how SAI deployment would affect human and natural ecosystems and existing studies provide divergent results. Research indicates that SAI could cause heterogeneous regional impacts. SAI co-benefits could include slowing permafrost degradation or reducing the rate of sea-level rise, while adverse effects could encompass changes to precipitation patterns, degradation of the ozone layer, shifts in ocean circulation, biodiversity degradation or the “termination effect” (rapid warming if SRM deployment is abruptly halted).

  • Nonprofit capacity building and public engagement in Low and Middle-Income Countries (LMICs), policy advocacy in High-Income Countries (HICs) and international governance needs support: Nonprofits work in the SRM field by conducting research, building research capacity, policy advocacy for research, engaging with the public and civil societies, and advancing international governance frameworks. Based on our analysis, we prioritized civil society engagement in Low and Middle-Income Countries (LMICs), policy advocacy in High-Income Countries (HICs) and advancing an international governance framework. We think that pushing forward with research, particularly outdoor experiments, without proper governance or stakeholder engagement could lead to undesirable outputs, such as a premature deployment by unilateral actors or a premature moratorium due to unregulated research.

  • Theory of change for philanthropic engagement: Research capacity building in LMICs and conducting research can lead to a better understanding of SRM's benefits and risks, thereby informing decision-making. Equipping civil society with knowledge around SRM, policy advocacy for research, and international cooperation could foster inclusive governance frameworks and evidence-based decision-making. It is not clear whether governance structures and informed decision-making would result either in a higher or lower likelihood of SRM deployment; however, we think it is the best way to ensure science-based and equitable considerations are forefront, avoid moral hazard, and reduce the possibility of unilateral or rogue actors.

  • Is there room for more funding? Even with an increase in government and philanthropic funding of SRM in recent years, we think the sector would be capable of absorbing more funding. We believe that nonprofit capacity building in LMICs, policy advocacy for research in HICs, and advancing international governance frameworks are important and receive less funding than conducting research and research capacity building.

  • Key uncertainties and open questions: Several uncertainties and open questions remain, including the high-level topic of whether work on SRM increases the risk of improper deployment (causing unexpected suffering), and whether exploring SRM would cause a moral hazard, slowing down mitigation efforts. We are additionally uncertain of how efforts to build SRM governance structures and advance research might influence each other and the level of consensus that should be required for decision-making on SRM.

  • Bottom line / next steps: Our understanding of the likelihood of SRM as a feasible and desirable way of limiting the rise in temperatures remains limited. Based on the scope for impact, feasibility and funding assessment, we think that nonprofit capacity building and public engagement and advancing governance frameworks are productive pathways to advance informed decision-making about SRM.

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