Climate intervention: what we need to know to respond to a climate emergency

Laxenburg, Austria – 03 August 2009. Even with aggressive global efforts to reduce greenhouse gas (GHG) emissions, scientists cannot rule out the possibility of rapid changes in the climate system, with potentially catastrophic consequences for society and the environment. The risk of such “climate emergencies” increases with higher GHG concentrations, emphasizing the urgency of global mitigation as the priority response to climate change. But what if a climate emergency develops despite the world’s best mitigation efforts?

In a report released today, an international team of scientists examine whether large-scale “geoengineering” could provide a rapid, if temporary, insurance response to avert the most severe consequences if such an extreme scenario does emerge. The report’s conclusion: it might be possible—but a lot more scientific research would be needed first.

The report authors—assembled and sponsored by Californian non-profit Novim—focus their scientific review and evaluation on one specific geoengineering proposal: the injection of tiny particles into the stratosphere, where they would reflect sunlight back into space and produce a global cooling, akin to that caused by the sulfur particles released during the eruption of large volcanoes. 

According to the report, while it appears technically feasible to produce rapid global cooling using such a technique, there is little understanding about what the regional impacts and risks might be, or what climate change impacts this ‘cooling’ may limit or avert.  

The report, “Climate engineering responses to climate emergencies,” is the first attempt to articulate the range of scientific questions that must be answered before such responses could be considered as a serious option.

“Cooling the planet by reflecting sunlight away from the Earth has been proposed by highly regarded scientists as a potential, short-term option for limiting some consequences of climate change”, says Dr. Jason Blackstock, from the International Institute for Applied Systems Analysis (IIASA) and one of the lead authors of the report. “But before any decision is taken about using such a technique, much better scientific understanding of the likely impacts is necessary. The aim of this study was to identify the research needed to reduce the large uncertainty surrounding these ideas.”

The questions identified in the report include: the many approaches on how to loft and disperse the particles into the stratosphere; to the potentially dangerous impacts on the climate system, including changes to stratospheric chemistry, and temperature and precipitation patterns; to the new observation systems that would be needed to monitor these climate impacts.

The report outlines a multi-stage, decade-long research and development (R&D) agenda that could begin to address the scientific questions identified by the authors. The later stages of this agenda would include field-tests of the techniques, which would be necessary to address many of the outstanding scientific and other questions. However the authors also highlight that such field-testing would involve risks and challenges that first need to be carefully studied.

Figure 1 Caption: The reduction of carbon emissions to limit the heat trapped by greenhouse gasses in the atmosphere is depicted to the left as the priority response for limiting the impacts of climate change. Increasing the amount of sunlight reflected by the Earth’s atmosphere by injecting tiny particles into the stratosphere is depicted to the right as a potential additional response—along with decreasing carbon emissions—to avert or limit severe consequences of climate change in the event of a climate emergency. ©NOVIM See greyscale image

“As we focused on the specifics of the R&D that would be required to determine the environmental risks of injecting particles into the stratosphere, we confronted a novel question regarding the scale of the experiment that would need to be conducted: Is there a scale that is large enough to determine the risks we are running but small enough not to bring on the possible negative outcomes we are concerned about?" said co-author Prof. Rob Socolow from Princeton University.

“The report does not advocate for geoengineering, but emphasizes the type of research that is needed to help us understand whether these rather extreme proposals could help, or even exacerbate a climate crisis," said co-author Dr. Ken Caldeira of the Carnegie Institution.

“Reducing GHG emissions must be our priority for limiting the impacts of climate change,” Dr. Blackstock emphasized. “However, if severe climate change impacts begin to appear, then governments may feel pressured to take extreme action—and extreme action may be warranted at some stage. But before there is any serious political consideration of these options, we need much better scientific understanding of the risks and benefits of geoengineering for our climate and global society.”

The full report J. J. Blackstock et al., Climate Engineering Responses to Climate Emergencies (Novim, 2009), is available online

For interviews please contact:

• Leane Regan, IIASA Communications Department, Tel: +43 2236 807 316 or +43 664 443 0368, E-mail: regan@iiasa.ac.at
• Michael Ditmore, Novim, Tel: +1 805 886 8887, E-mail: ditmore@novim.org

More information:

• Jason Blackstock, IIASA, Tel: +1 617 401 8232, E-mail: jjb@iiasa.ac.at
• Rob Socolow, Princeton, Tel: +1 609 258 5467, E-mail: socolow@princeton.edu
• Ken Caldeira, Carnegie Institution, Tel: +1 650 704 7212, E-mail: kcaldeira@carnegie.stanford.edu

About Novim
Novim, based in Santa Barbara, California is a non-profit scientific corporation that convenes small collaborative groups of the world’s leading experts to identify and analyze scientific and technological issues of global importance.

Its findings are published online at its Web site and uploaded to scientific archives. Results will also be made available in the form of classroom study guides, videos and perspective summaries aimed at policy makers and the public in general.

“Climate engineering responses to climate emergencies” is Novim’s first report.

About IIASA:
IIASA is an international scientific institute that conducts research into the critical issues of global environmental, economic, technological, and social change that we face in the twenty-first century. Our findings provide valuable options to policy makers to shape the future of our changing world.

IIASA is independent and funded by scientific institutions in Africa, the Americas, Asia and Europe.

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Last updated: 03 Sep 2009