Feature articles

Climate Change — Beyond the tipping points?
A growing number of scientists have begun asking what might be done to curb the negative impacts of climate change, particularly under worst-case “emergency” scenarios; the answer they keep coming back to is geoengineering.

Since the last Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC), a mounting body of evidence has suggested that climate change will, in fact, be more severe and more rapid than the median AR4 estimates. In particular, concerns about possible climatic “tipping points” have some climate scientists now talking about a possible “climate emergency” within their lifetime. Against this backdrop of scientific concern, global carbon emissions continue to accelerate (i.e., the rate of emissions increase is itself increasing).

Geoengineering schemes can be divided into two distinct categories—carbon dioxide removal (CDR) and solar radiation management (SRM). Both have the two main characteristics that define “geoengineering”—they involve intentional alterations to the climate system, and their impacts would be global (or close) in scale. Moreover, both have been the subject of major scientific review studies in 2009 led in part by IIASA’s Jason Blackstock.

The first of these studies focused on schemes to inject sulfur aerosols into the stratosphere, which IIASA Institute Scholar and Nobel laureate Paul Crutzen drew considerable scholarly and public attention to in 2006 with a paper in Climatic Change. The new study report, released in July 2009 and lead-authored by Blackstock, found that while such techniques could cool the planet rapidly in an “emergency situation,” there are very large uncertainties regarding the impacts on the climate of stratospheric aerosol injection. The report outlines a substantial program of further scientific research needed to improve our understanding of such aerosol options.

The second study currently being coordinated by Blackstock focuses on chemically engineered CDR techniques. The report, expected out in early 2010, will discuss why (similar to mitigation) such techniques would take decades to have significant climatic impacts. The study will, however, also highlight promising avenues for expanded scientific research.

These two review studies are also complemented by a third, conducted this year by the United Kingdom’s Royal Society. Released in September 2009, the Royal Society’s report provides a broad overview of all geoengineering schemes, and highlights the key differentiating characteristics of SRM and CDR techniques explored in detail by the other studies—most importantly: timescale of impact, and ability to effectively ameliorate greenhouse gas–induced climate change. Where SRM’s rapid cooling effect with highly uncertain additional impacts make it a candidate response to a “climate emergency” scenario, CDR’s slow but expected effective amelioration of climate change (because it removes the root cause) makes it more viable as a long-term complement to drastic carbon emission reductions, enabling eventual negative emission scenarios.

Of course, research into geoengineering does not occur in a vacuum. And as IIASA alumnus and Nobel Laureate Thomas Schelling pointed out in his 1996 Climatic Change article, serious consideration of geoengineering will impact nations’ strategic perceptions and actions toward mitigation.

To begin addressing these issues, Blackstock is now organizing a series of side events at the UN Climate Change Conference in Copenhagen, as a partnership between the Royal Society, the Centre for International Governance Innovation, the International Institute for Sustainable Development, the Stockholm Environment Institute, and IIASA. These events will include short overview presentations of the science and governance challenges associated with geoengineering research, followed by panel discussions focusing on emerging issues. The two goals for these events are to encourage discussion of these issues among a broader community of policymakers and researchers and to promote global cooperation on the policy and governance dimensions of geoengineering research.

Further information

A list of reference material is available online.

Dr. Jason J. Blackstock is a Postdoctoral Research Scholar in IIASA’s Risk and Vulnerability Program, and a Fellow at the Centre for International Governance Innovation (Waterloo, Canada).

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Last updated: 08 Jul 2010