Climate Intervention Reflecting Sunlight to Cool Earth (2015) / Chapter Skim
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A fourth, more speculative family of approaches called albedo modification seeks to offset climate warming by greenhouse gases by increasing the amount of sunlight reflected back to space.1 Albedo modification techniques mask the effects of greenhouse warming; they do not reduce greenhouse gas concentrations (see Box S.1 for definitions of key terms)
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. Carbon Dioxide Removal -- intentional efforts to remove carbon dioxide from the atmosphere, including land management strategies, accelerated weathering, ocean iron fertilization, bioenergy with carbon capture and sequestration, and direct air capture and sequestration.
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CARBON DIOXIDE REMOVAL READY FOR INCREASED RESEARCH AND DEVELOPMENT Some CDR strategies seek to sequester carbon in the terrestrial biosphere or the ocean by accelerating processes that are already occurring as part of the natural carbon cycle and which already remove significant quantities of CO2 from the atmosphere. These approaches have challenges and risks that need to be assessed, including verifying and monitoring the amount of carbon removed, incomplete understanding 3
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NOTE: GHG stands for greenhouse gases released by human activities and natural processes and includes carbon dioxide, methane, nitrous oxide, chlorofluorocarbons, and others. The committee intends to limit discussion to proposals that raise the fewest problematic issues, thus excluding ocean iron fertilization from the CDR list.
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In the end, any actions to decrease the excess burden of atmospheric CO2 serve to decrease, or at least slow the onset of, the risks posed by climate change. Environmental risks vary among CDR approaches but are generally much lower than the risks associated with albedo modification approaches.
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ALBEDO MODIFICATION PRESENTS POORLY UNDERSTOOD RISKS Proposed albedo modification approaches introduce environmental, ethical, social, political, economic, and legal risks associated with intended and unintended consequences. However, there are both theoretical and observational reasons to believe that albedo modification has the potential to rapidly offset some of the consequences of global warming at an affordable cost.
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Direct costs of deployment of a stratospheric aerosol layer of sufficient magnitude to offset global mean radiative forcing of CO2 have been estimated to be at least an order of magnitude less than the cost of decarbonizing the world's economy. Although these cost estimates do not include an appropriate monitoring system or indemnification for damages from albedo modification actions, they are small enough that decisions are likely to be based primarily on considerations of potential benefits and risks, and not primarily on the basis of direct cost.
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The committee considers it to be irrational and irresponsible to implement sustained albedo modification without also pursuing emissions mitigation, carbon dioxide removal, or both. Climate models indicate that the combination of large-scale albedo modification with large-scale CO2 increases could lead to a climate with different characteristics than the current climate.
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For example: • despite mitigation and adaptation, the impacts of climate change still be If, come intolerable (e.g., massive crop failures throughout the tropics) , society would face very tough choices regarding whether and how to deploy albedo modification until such time as mitigation, carbon dioxide removal, and adap tation actions could significantly reduce the impacts of climate change.
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Much of the required research on albedo modification overlaps considerably with the basic scientific research that is needed to improve understanding of the climate system. Examples of such "multiple benefit research" -- research that can contribute to a better understanding of the viability of albedo modification techniques and also a better understanding of basic climate science -- include conducting research on clouds and aerosols, maintaining the continuity of measurement of the top-ofatmosphere radiation budget, and monitoring ocean-atmosphere energy exchange through programs such as the Argo float system.
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should be well-enough under tood to be s benign to the larger environment, should be conducted at the smallest practi cal scales, should be designed so as to pose no significant risk, and should be planned subject to the deliberative process outlined in Recommendation 6. Recommendation 5: The committee recommends that the United States improve its capacity to detect and measure changes in radiative forcing and associated changes in climate.
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However, such research is not specifically addressed by any federal laws or regulations. Given the perceived and real risks associated with some types of albedo modification research, open conversations about the governance of such research, beyond the more general research governance requirements, could encourage civil society engagement in the process of deciding the appropriateness of any research efforts undertaken.
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CONCLUDING THOUGHTS Addressing the challenges of climate change requires a portfolio of actions that carry varying degrees of risk and efficacy. CDR strategies and other technologies and approaches that reduce net emissions (e.g., carbon capture and sequestration, noncarbon-based energy, and energy efficiency improvements)
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In contrast, even the best albedo modification strategies are currently limited by unfamiliar and unquantifiable risks and governance issues rather than direct costs. The committee reiterates that it is opposed to climate-altering deployment of lbedo a modification techniques, but it does recommend further research, particularly m ultiple-benefit research that furthers the basic understanding of the climate system and seeks to quantify the potential costs, consequences (intended and unintended)
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