Policy ForumClimate Change

The Politics of Geoengineering

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Science  29 Jan 2010:
Vol. 327, Issue 5965, pp. 527
DOI: 10.1126/science.1183877

Despite mounting evidence that severe climate change could emerge rapidly, the global reduction of carbon emissions remains alarmingly elusive (1, 2). As a result, concerned scientists are now asking whether geoengineering—the intentional, large-scale alteration of the climate system—might be able to limit climate change impacts. Recent prominent reviews have emphasized that such schemes are fraught with uncertainties and potential negative effects and, thus, cannot be a substitute for comprehensive mitigation (3, 4). But as unabated climate change could itself prove extremely risky, these reviews also recommend expanding geoengineering research. As such research is considered (57), a process for ensuring global transparency and cooperation is needed.

Geoengineering schemes can be divided into two very different categories: carbon dioxide removal (CDR) and solar radiation management (SRM) (4). CDR schemes such as direct air capture (8) or ocean fertilization (9) would remove the cause of climate change. However, technical challenges and large uncertainties surrounding large-scale CDR deployment, along with long delays in the climatic response to carbon forcing, mean that it would take decades to have notable effect (4).

Conversely, SRM could substantially influence the climate in months, but with much greater uncertainty about the net effects. SRM schemes such as stratospheric aerosols and cloud brightening aim to cool the planet by reflecting a fraction of the incoming sunlight away from Earth. “Natural experiments” caused by volcanoes have demonstrated the rapid impact potential of SRM, and such schemes should be technically simple to deploy at low cost, relative to mitigation (3, 4). But SRM would at best unevenly ameliorate regional climatic change and may have serious unintended consequences. For example, SRM could produce droughts and delay the recovery of the ozone layer by decades, while doing almost nothing to address ocean acidification. SRM is thus not a substitute for mitigation (3, 4).

Despite the limitations and risks, banning responsible SRM research would be a mistake. The ability to rapidly influence the climate means SRM might be the only recourse should a climate crisis materialize. Moreover, the rapid impact, simple deployment, and low cost of SRM schemes make unilateral deployment a very real concern (10). More knowledge will help us craft good international governance and avoid rash unilateral actions.

Until recently, SRM research was largely politically benign, as it consisted only of model studies published in the open literature (3). In contrast, emerging laboratory-based development of SRM technologies raises the prospect that national or corporate interests might try (or appear to try) to control or profit from these schemes. Such a perception would be particularly likely if SRM research were framed in terms of national security, especially if the results were classified (11).

Field tests of such technologies can exacerbate these issues. Subscale field experiments designed to have demonstrably negligible environmental and transboundary impacts, such as those recently conducted in Russia (12), can be valuable for testing technologies and identifying the environmental risks of scaling up. But the controversy surrounding a 2009 Indo-German ocean fertilization experiment highlights both the difficulty of proving that the risks of any geoengineering field test are in fact demonstrably negligible, and the political sensitivities such tests can evoke (13).

As such, nations must carefully consider the signals that any unilateral field test sends to the international community. If conducted without international approval, a test perceived (even just politically) to present transboundary risks could spark international tensions, creating a global “crisis of legitimacy” (10). For subscale testing, we need politically acceptable scientific standards and oversight mechanisms for ensuring demonstrably negligible impacts.

Eventually, confirming the effectiveness of an SRM scheme would require large-scale tests with demonstrable climatic impacts—essentially low-level deployment. But because of the complexity and variability of the climate, it will be extremely difficult to attribute impacts and unintended consequences to any test (3, 14). This means liability for damages, real or perceived, would become a political challenge. For example, if the Asian or African monsoon were to weaken in a year following an SRM test—at the edge of natural variability, but still causing droughts and food shortages—uncertainty about causation could fuel accusations of responsibility.

As a first step to addressing some of these issues, scientists should propose international norms and best practices for research (10). The upcoming Asilomar conference on Climate Intervention Technologies in March 2010 will bring together ∼150 scientists to begin this process. However, although necessary, such norms are not sufficient.

Issues of acceptable risk for subscale testing; if, when, and where climatic impacts testing should begin; or how SRM technologies should be managed are not just scientific. Such questions require a broadly accessible, transparent, and international political process. Vulnerable developing countries so far absent from SRM discussions must be engaged, and all stakeholders need to consider whether existing frameworks can facilitate this process, or whether new forums, treaties, and organizations are required.

Emerging national research programs—and even individual scientists—must forswear climatic impacts testing and carefully restrict subscale field-testing until approved by a broad, legitimate international process. All SRM research should be in the public domain and should be integrated into any subsequent international research framework. Programs should include international collaboration, communicate with developing nations, and prioritize research that has global versus national benefits. These steps will limit the new problems geoengineering research heaps on an already strained global climate agenda, preserving options for future international cooperation.

References and Notes

  1. U.S. Congressional and U.K. parliamentary hearings on geoengineering have recently been convened; see science.house.gov/press/PRArticle.aspx?NewsID=2676.
  2. In 2009, the European Union began the IMPLICC geoengineering research project (http://implicc.zmaw.de/).
  3. The U.K. Research Councils Energy Programme announced support for new geoengineering research; see www.epsrc.ac.uk/Content/News/geoengineering.htm.

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