Ignorance is not an option

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Science  20 Mar 2015:
Vol. 347, Issue 6228, pp. 1293
DOI: 10.1126/science.aab1102

Suppose future governments of the world discover that a single nation is taking the unprecedented action of spraying sulfur dioxide into the stratosphere to cool Earth's surface temperature by a few degrees celsius? The move is intended to increase the fraction of solar energy that is reflected from Earth back into space—a measure known as modifying Earth's albedo. The nation was prompted by a failed harvest the previous year, the result of greenhouse gas buildup in the atmosphere that boosted average summer temperatures above 32°C. National leaders turn to the science community for answers: What does this action mean for any individual country? Will it make the drought in Saõ Paolo better or worse? If the wheat yield falls in northern Russia, could it be due to the albedo modification? Can science apportion damage caused by such an intervention? Should the United Nations block such action?

“leaders…must be equipped with an understanding of the risks… that an albedo modification action might present.”


For the moment, this scenario remains hypothetical. However, the impacts of climate change are indeed real. Before long, they may well provoke citizens to demand that their leaders take more drastic actions for the sake of the economy and public health, and to avoid civil unrest and international conflict. If world leaders are to respond effectively, they must be equipped with an understanding of the risks in all dimensions, including environmental, political, social, and economic, that an albedo modification action might present.

As demonstrated by the effects of large volcanic eruptions that inject particles into the stratosphere, albedo modification is the only option on the table that is known to cool Earth's surface quickly. Given that greenhouse gas emissions continue to rise globally, the risks of not knowing more about the effects, hazards, and intended and unintended consequences of this procedure are starting to outweigh the risks of conducting research to learn more about it. For this reason, a recent U.S. National Research Council (NRC) report,* written by a committee that I chaired, says that more research is needed on albedo modification so that the scientific community can answer questions such as those posed in the scenario above. The committee also advocates the need for improved capacity to detect and measure changes in radiative forcing (the difference between solar energy absorbed by Earth and radiated back to space) that are associated with changes in albedo, and the resulting effects on climate. In particular, the committee prioritizes research directed at poorly constrained climate parameters, such as Earth's radiation balance, as well as studies that address the human dimensions of albedo modification, such as the ethical, economic, and legal aspects. Some very smallscale field research might be justified, but only under governance that involves civil society in decisions on what should be allowed in order to advance understanding while reducing risk.

A few scientists and members of the general community have responded to the report's recommendations with the concern that it is dangerous to discuss albedo modification openly and to propose research. The committee considered very carefully the “double moral hazard” that conducting research could lead society to regard albedo modification as an easy “backup plan” to needed mitigation and adaptation measures, whereas forgoing research could lead to irresponsible deployment of albedo modification without appropriate information on its likely consequences. Both communities expressed fear that research will lead to inevitable deployment. The committee hopes that the NRC report will stir widespread concern about the prospect of albedo modification as a response to climate change. While very strongly recommending against deployment of this measure at climate-altering scales at this time, the report's first recommendation is to implement climate change mitigation and adaptation strategies: the lowest-risk options. Although we hope that a scenario like the one above will not present itself, society is no longer at the point where ignorance about albedo modification is acceptable.

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