Burning Bush
THREE months ago, George Bush's fledgling administration dropped two public-relations bricks over the issue of global warming. First, Mr Bush refused to stand by his campaign pledge to regulate emissions of carbon dioxide, a greenhouse gas that is widely believed to be a big cause of global warming. That sparked a backlash from American environmentalist groups. Second, he annoyed a lot of people overseas by trumpeting, in undiplomatic terms, his long-standing opposition to the Kyoto Protocol. This is a United Nations treaty agreed to (though not yet much ratified) by most industrialised countries, that calls for binding cuts in greenhouse-gas emissions. To defuse the rows over these two dropped bricks, the Bush team promised to come up with a credible alternative policy that was more than mere Kyoto-bashing. And to help form that policy it called, on May 11th, on the services of the National Academy of Sciences (NAS) to provide guidance on the matter as soon as possible. America's most prestigious scientific body hastily organised an expert panel under the chairmanship of Ralph Cicerone of the University of California, Irvine, to meet that request, and the results of its deliberations have just been released. The first paragraph of the report says it all: Greenhouse gases are accumulating in Earth's atmosphere as a result of human activities, causing surface air temperatures and subsurface ocean temperatures to rise. Temperatures are, in fact, rising. The changes observed over the last several decades are likely mostly due to human activities, but we cannot rule out that some significant part of these changes are also a reflection of natural variability. Human-induced warming and associated sea level rises are expected to continue through the 21st century.Now will you believe it? The NAS's conclusions, which include no new data, will come as no surprise to those working in the field. They more or less confirm a recent report from the United Nations' Inter-governmental Panel on Climate Change (IPCC) that laid out the scientific case for taking global warming seriously. What they do provide is political cover, if Mr Bush wishes to use it, for a graceful retreat. Many Americans were, for various reasons, unwilling to accept the authority of a UN-sponsored study. A home-grown one is not subject to any such political caveats. The administration left itself remarkably little wiggle-room in the mandate that it gave Dr Cicerone. The panel was asked not only about the certainties and uncertainties surrounding the science of climate change, but also about the worth of the UN report and its conclusions. In particular, it was asked explicitly whether there were substantive differences between the IPCC's scientific reports (lengthy tomes detailing the state of climate science) and the summary for policymakers (which suggests that there is enough scientific evidence to warrant action now). Critics of the Kyoto treaty have long argued that this summary can only have been the result of political sleight of hand. That always looked unlikely. After all, the evidence was alarming enough as long ago as 1992 for Mr Bush's father to sign a UN treaty in Rio de Janeiro that was intended to fight global warming. This treaty is the framework for the Kyoto process. Since then, new evidence has confirmed that global warming should be taken seriously. The IPCC's summary report went so far as to declare that man's actions have contributed substantially to the observed warming over the last 50 years. An earlier IPCC report had predicted that, if current trends continued, the temperature of the atmosphere could rise by 1.0-3.5C by 2100; the latest one expanded the range of likely warming to 1.5-6.0C. This is not to say that no uncertainties remain. On the contrary, the NAS panel is frank about how much of the science is still hazy. In particular, its report highlights the role of aerosols (small, airborne and often man-made particles that reflect sunlight and thus cool the atmosphere, rather than warming it). It also comments on the inadequacy of existing computer models of climatic change, and the current lack of understanding of the feedback loops that influence the sensitivity of the climate to increases in greenhouse gases. Such feedback loops might slow any warming trend; but they might, on the other hand, accelerate it. And, although the NAS offers a likely temperature range for the next century that is slightly less alarming than the IPCC's, and it attaches more provisos and caveats to its conclusions than the UN panel did, it nevertheless leaves little doubt that global warming should be taken seriously. Indeed, the NAS's endorsement of the UN panel is striking: The IPCC's conclusion that most of the observed warming of the last 50 years is likely to have been due to the increase in greenhouse gas concentrations accurately reflects the current thinking of the scientific community on this issue...The full IPCC Working Group I report is an admirable summary of research activities in climate science, and the full report is adequately summarised in the Technical Summary. The NAS also rejects the insinuation, apparent in the questions from Mr Bush's team, that the UN process was politically manipulated. It is true, it explains, that the IPCC summary reflects less emphasis on communicating the basis for uncertainty and a stronger emphasis on areas of major concern associated with human-induced climate change. However, rather than blaming some socialist skulduggery, the authors suggest that this change in emphasis appears to be the result of a summary process in which scientists work with policy makers. It notes that no changes were made without the consent of the IPCC's lead authors, and opines that most of the changes that did occur lacked significant impact. The result is bad news for those who had hoped for a rejection of the IPCC's conclusions. And, though the sceptics on the NAS panel itself have rushed to make it clear that their report does not, in any way, endorse Kyoto, that is largely because the report offers no views whatsoever on any policy options. Nobody who takes this report seriously can easily argue for doing nothing. What Mr Bush himself will do is not yet clear. He has accepted the results of the study, and acknowledged the report's chief conclusion that global warming is real and at least partly man-made. And, though he has once again rejected the Kyoto pact as fatally flawed, he has also accepted that an international, UN-led approach is the right way to deal with this most global of problems. However, he has yet to offer any credible alternative to the Kyoto deal. His immediate response this week was to offer to spend more government money on climate science and greenhouse gas-related technology. Those are certainly worthy causes, but they do not address the central point. A bigger plan is needed, and it would be politically convenient if at least its outlines were clear within the next few weeks. The next round of talks on the UN pact are scheduled for July in Bonn. If the Americans have nothing to offer by then, they will run into a lot more criticism.