In November of 1965, the Environmental Pollution Panel of the President's Science Advisory Council (PSAC) for the first time informed a president of the United States about the threats posed by increasing atmospheric CO2 concentrations. Their report stated:
The climatic changes that may be produced by the increased CO2 content could be deleterious from the point of view of human beings. The possibilities of bringing about countervailing climatic changes therefore need to be thoroughly explored. A change in the radiation balance in the opposite direction to that which might result from the increase of atmospheric CO2 could be produced by raising the albedo, or reflectivity, of the earth (PSAC, 1965).
The topic of SRM was also taken up in the National Research Council's 1992 report Policy Implications of Greenhouse Warming (NRC, 1992b). That report noted:
[W]e are at present involved in a large project of inadvertent "geoengineering" by altering atmospheric chemistry [i.e., by increasing GHG concentrations], and it does not seem inappropriate to inquire if there are countermeasures that might be implemented to address adverse impacts Our current project of "geoengineering" involves great uncertainty and risk. Engineering coun-
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FIGURE 15.1 Various geoengineering options, including both solar radiation management and carbon dioxide removal. Dashed boxes represent carbon reservoirs (e.g., soil, ocean); black arrowheads represent shortwave radiation and are associated with solar radiation management; white and gray arrowheads pointing down correspond to a variety of natural and engineered processes, respectively,for removing C02 from the atmosphere; the thicker, gray arrowhead pointing up represents enhanced ocean upwelling, which could conceivably help to remove C02 from co the atmosphere by enhancing biological activity at the ocean's surface; and the thinner gray arrowheads correspond to increased cloud conden-sation nuclei sources. SOURCE: Lenton and Vaughn (2009).
termeasures need to be evaluated but should not be implemented without broad understanding of the direct effects and potential side effects, the ethical issues, and the risks.
The PSAC (1965) and NRC (1992b) reports suggested that proposals to increase the reflectivity of the Earth (and to remove GHGs from the atmosphere) be thoroughly examined. This sentiment was echoed by many participants at the geoengineering workshop held in June 2009 as part of the suite of activities for the America's Climate Choices study (Appendix F), as long as such research does not undermine other critical climate research efforts (see the discussion of ethical issues below), including research on adapting to the impacts of climate change and on conventional strategies for limiting the magnitude of future climate change (i.e., reducing fossil fuel consumption, deforestation, and other activities that contribute to climate forcing). Critically, these evaluations should explore the intended effects of geoengineering approaches and their potential unintended side effects, as well as the ethical, institutional, social, and political aspects of intentional manipulation of the climate system.
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