Geoengineering: A Revolutionary Approach to Climate Change
About This Event

For more than twenty years, policymakers have struggled to find ways to reduce greenhouse gas emissions enough to stop global climate change. Congress is likely to enact federal climate legislation in 2009, but many scientists fear that emissions reductions may not occur quickly enough to prevent significant warming. Some scientists Listen to Audio

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also fear that potentially catastrophic effects, such as the melting of the polar ice caps, could happen unexpectedly quickly. If warming proves to be uncontrollable and dangerous, what could we do?

A growing number of climate scientists believe that there may be only one possible answer to that question: change features of the earth’s environment in ways that would offset the warming effect of greenhouse gases, a concept known as “geoengineering” (or “climate engineering”). The most plausible way of doing this would be to use very fine particles in (or above) the stratosphere to block a small fraction (roughly 2 percent) of sunlight. While geoengineering science is in its infancy, most scientists who have studied the idea believe it is likely to be feasible and cost-effective.

Is geoengineering feasible? What do scientists know about it--and what do they need to learn if we want to have the option of deploying these technologies in an emergency? If geoengineering proves to be feasible, would it be desirable? What are the policy implications of this revolutionary idea? What should it mean for the current debate over climate policy in Congress and for international climate negotiations? Who would benefit from geoengineering? Which countries might object--and how should their concerns be addressed?

To explore these and other questions, Lee Lane and Samuel Thernstrom will host a series of AEI conferences that will present the findings of original commissioned research papers on the policy implications of geoengineering. Speakers at this event will provide a broad overview of the state of the science of geoengineering and the range of public policy questions raised by this revolutionary concept. Tom Wigley, senior scientist at the National Center for Atmospheric Research, will examine the state of the science; Kerry Emanuel of the Massachusetts Institute of Technology and Vaughan Turekian of the American Association for the Advancement of Science will comment. Subsequently, Johns Hopkins University professor Scott Barrett will explore the policy implications of geoengineering, followed by commentary from Fred Iklé of the Center for Strategic and International Studies.

12:45 p.m.
Panel I: The Science of Geoengineering
Tom Wigley, National Center for Atmospheric Research
Kerry Emanuel, Massachusetts Institute of Technology
Vaughan Turekian, American Association for the Advancement of Science
Samuel Thernstrom, AEI
Panel II: The Implications of Geoengineering for Climate Policy
Scott Barrett, Johns Hopkins University
Fred Iklé, Center for Strategic and International Studies
Lee Lane, AEI
Event Summary

Is Geoengineering a Revolutionary Approach to Climate Change?

WASHINGTON, JUNE 5, 2008 -- As Congress debates legislation to mandate reductions in greenhouse gas emissions, another type of intervention to reduce global warming--geoengineering--has gone largely unexamined by lawmakers. On June 3, the American Enterprise Institute held the first in a set of conferences to examine the science and policy implications of geoengineering, hosted by AEI scholars Lee Lane and Samuel Thernstrom. As AEI president Christopher DeMuth noted in his introduction, mitigating greenhouse gases is very expensive, but while scientists and engineers have been discussing geoengineering for years, it has not made its way into policy discussions.

There was general agreement among both the scientists and social scientists who spoke that geoengineering is not a panacea, but that it does have potential for slowing down or halting climate change without some of the problems and costs of greenhouse gas mitigation.

If mitigating climate change through reductions in greenhouse gas emissions were cheap, or if the benefits of doing so were large, Scott Barrett of John Hopkins University noted, it would already have been done. In fact, while current technology would allow us to make small emissions cuts relatively cheaply, major reductions would be extremely expensive and require major economic sacrifices. In addition, global climate change may be, as Barrett declared, "the world's greatest collective action problem," since no country acting alone can reduce greenhouse gases enough to slow climate change. Lane agreed, saying that no mitigation-based solution is possible without China's participation. He said that the United States has very little ability to persuade China to act to reduce its fast-growing emissions.

Geoengineering may be a way to solve this collection action problem. Several different types of interventions have been discussed and modeled. Tom Wigley, a scientist at the National Center for Atmospheric Research, discussed how injecting ultra-fine sulfur particles into the stratosphere or spraying clouds with saltwater to increase their reflectivity could reduce climate change. Estimates for how much a solution like this would cost are not definitive, since research has been limited and no field testing has been done, but if geoengineering proves feasible, it is likely that it would be far less expensive--and would require less extensive global cooperation--than mitigation.
Geoengineering has its limits, though: some of the problems associated with carbon dioxide emissions, such as ocean acidification and its possible impacts on marine life, would require other solutions. Wigley presented geoengineering as a possible way to buy more time to create new ways to produce low-cost clean energy, which would make mitigation cheaper. As Thernstrom noted, the Intergovernmental Panel on Climate Change's estimates of future technological progress may be excessively optimistic: its predictions assume that, even without policy changes, new technologies will significantly reduce carbon intensity. In fact, Thernstrom added, even with drastic policy changes, we will probably not reach the low emissions levels that many scientists recommend. Wigley and Massachusetts Institute of Technology professor Kerry Emanuel agreed, however, that mitigation will in the long run have to be a central feature of how people deal with climate change.

Barrett cited a recent report from the Peter G. Peterson Institute for International Economics finding that although agricultural productivity in some countries is likely to suffer from gradual global warming, other countries would actually see their agricultural output increase. Abrupt climate change will not help any countries, Barrett said, so geoengineering is particularly likely to be attempted if the probability of abrupt climate change rises.

The conference participants widely agreed that more research needs to be done into geoengineering. For instance, very little modeling has been done on the regional effects of technical solutions to global warming: climate systems are complex, and an intervention that brings down the average global temperature might also change regional weather patterns, such as the length or intensity of the monsoon season.

Geoengineering is gaining acceptance in mainstream climate science, but funding is still very limited and only a few of scientists are studying the concept. Eventually, geoengineering experiments will have to done in the real world, outside the realm of computer simulations. This will present a major policy challenge for world leaders--and a different kind of collective action problem than mitigating greenhouse gases. Nevertheless, Fred Iklé of the Center for Strategic and International Studies remarked, it is important for governments--especially that of the United States--to act on proposals for serious research and development on geoengineering.


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AEI sponsors research into climate change and environmental policy.

For more information about environmental policy studies at AEI, visit or contact Abigail Haddad at [email protected] or 202.862.7165.

For media inquiries, contact Véronique Rodman at [email protected] or 202.862.4870.


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  • Samuel Thernstrom has studied and written about environmental issues for twenty years, with a particular emphasis on global climate change. He served on the White House Council on Environmental Quality prior to joining AEI in 2003. As codirector of the AEI Geoengineering Project, Mr. Thernstrom studied the policy implications of geoengineering, or climate engineering. This groundbreaking field of climate science involves changing features of the earth's environment to offset the warming effect of greenhouse gases. He has been published on and in the Los Angeles Times and the Washington Post, and he has appeared on BBC News, ABC News, CNN, FOX News, NPR, and The NewsHour with Jim Lehrer on PBS.
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