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- Solar radiation management would seek to enhance and manage the atmosphere's natural reflective qualities.
- In contrast to greenhouse gas control, solar radiation management may offer a cost-effective way of managing the risk of crossing climate tipping points.
- If climate change is a significant problem, then solar radiation management could be part of a significant solution.
- Effective greenhouse gas control would require a hefty willingness to pay for it in Beijing, Delhi, Moscow, and Washington.
Measures to reduce greenhouse gas (GHG) emissions have long dominated public discourse about responses to man-made climate change. However, major institutional and political hurdles dim future prospects for controlling emissions. While adaptation to climate change can accomplish much, flawed institutions are likely to limit its efficacy.
Solar radiation management (SRM) appears to promise at least some capacity to offset the warming caused by the rising atmospheric GHG concentrations. SRM would seek to enhance and manage physical processes that currently reflect sunlight back into space. For example, most researchers have envisioned implementing this concept by adding to the layer of sulfuric acid that is already present in the lower stratosphere. All else remaining equal, global mean temperatures would fall even though GHG levels would not; the Intergovernmental Panel on Climate Change estimates that physical processes such as these already offset about 40 percent of global warming. By lessening the rise in temperature, SRM might lessen some of the risks of global warming.
Recent technical developments have advanced our understanding of important aspects of SRM. First, the regional impacts of SRM will be variable and these differences are likely to become a source of disagreement regarding SRM deployment. Second, given the uncertainties about SRM technologies, there is a pressing need for research and development funding. Third, in contrast to GHG control, SRM may offer a cost-effective way of managing the risk of crossing climate tipping points.
The debate over SRM continues to evolve slowly. Two trends are visible. First, climate change as an issue has lost political salience. Second, SRM’s visibility has been rising. The greater focus on SRM has led to a growing debate about its proper governance. So far, only a very narrow range of experts and interests have joined this debate. Even so, no consensus seems to be at hand. Disagreement exists even among environmental advocacy groups.
The economic benefits of a successful SRM program would flow from a reduction in climate damages owing to warming, and a reduction in economic damage caused by GHG controls. Determining the optimal amount of GHG controls to implement in the presence of SRM is an ongoing research effort. Some argue (1) that SRM should be held in reserve and only used in the case of an “emergency,” which is never precisely defined, and (2) that no change should be made to plans for emissions reductions such as they are. Others suggest that SRM may augment an emissions reduction program by providing near-term benefits and risk reduction while low carbon energy sources are developed.
SRM’s precise value remains uncertain; however, it seems clear that its potential benefit is very large—on par with the damages brought by climate change itself. In other words, if climate change is a significant problem, then SRM could be part of a significant solution.
The incentives for using SRM appear to be stronger than those for GHG control. Much analysis has used this valid point to conjecture that SRM would be easy to deploy—indeed, that it would be too easy. This fear is largely misguided. Global power politics militate against any state bidding for sole control of an SRM system. In short, SRM remains a speculative option; nonetheless, a workable SRM system could offer a highly useful backup and supplement to current policy options.