This month鈥檚 summary report from the International Panel on Climate Change makes compelling reading. There is not a great deal that is new, but its account of what is now the unequivocal science of climate change is peppered with hard-hitting statements of the 鈥渧ery likely鈥� and the 鈥渆xtremely likely鈥�.
This was, of course, its purpose: to remove contentious and uncertain findings, and nail down the basic narrative of climate change in a way that stifles the squawking of the sceptics and puts the squeeze on governments still looking for excuses for inaction. As one lead author, the American glaciologist Richard Alley, put it at the publication of the summary in Paris last week: 鈥淭he basic picture is unchanged, but it just keeps building up. We can now pound the table and say we鈥檝e got it sorted.鈥�
Was this a political decision on the part of scientists? None would admit as much. But Achim Steiner, director of the UN Environment Programme, one of the IPCC鈥檚 sponsors, was clearly on message when he sat beside them and declared: 鈥淔ebruary 2nd will be remembered as the date when question marks were removed on whether climate change has anything to do with human activity 鈥� the moment when attention will shift to what on earth we are going to do about it.鈥�
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This desire for a consensus of certainty comes at a price. The rising tide of concern among researchers about positive feedbacks in the climate system is not reflected in the summary (see What the IPCC didn鈥檛 tell us ). The authors acknowledge that they were being conservative. There is, though, a thin line between being conservative and being misleading, and on occasions the summary crosses that line. It omits some very real risks either because we have not yet pinned down their full scale or because we do not yet know how likely they are. We must hope that when the complete report appears it will give much greater attention than the summary to the fate of the Greenland and West Antarctic ice sheets, Siberian permafrost, the Gulf Stream and rainforest soils.
The IPCC鈥檚 efforts are creating a bedrock of scientific certainty, but don鈥檛 expect this to silence the sceptics. With one or two exceptions, they are masters of spin rather than science. They have no alternative narrative for the state of the climate, and merely hop from one perceived uncertainty to the next: cosmic rays or little ice ages, urban heat islands or the social pathology of climate scientists. Last week, one prominent critic even accused the IPCC of stating the obvious.
Having arrived at its certainties, what should the IPCC do next? One clear need is to get to grips with the feared positive feedbacks. That means quantifying them in a way that allows them to take their place among other drivers of climate change in the models. Several of the IPCC scientists who spoke to New 杏吧原创 last week also want to move on from an emphasis on average temperatures and sea levels, and make specific projections that are more concerned with extremes 鈥� making their forecasts more like weather forecasts, in fact. It is, after all, the extremes 鈥� whether droughts or floods, heat waves or storms 鈥� that really impact on our lives.
Londoners, for example, care less about average sea levels than whether a storm surge in the North Sea will one day flood their homes. The French want credible forecasts of how often to expect more heat waves like the one that killed 20,000 people in 2003. Americans want the low-down on future hurricanes. Half the world needs a prognosis for El Ni帽o. 鈥淲e want seamless predictions that can go from weather forecasts, through predicting the ocean processes behind variables like El Ni帽o and Atlantic hurricanes, right up to the big climate picture,鈥� says Kevin Trenberth of the US National Center for Atmospheric Research. Five years ago, that would have been a pipe dream, but the pace of advance in computing power is making such forecasts possible.
Whatever the future direction of the IPCC, we now know enough to make climate change the challenge of the 21st century. One of the most corrosive contributions of climate sceptics has been to promote any uncertainty as an excuse for inaction. In truth, the remaining uncertainties should be making us redouble our efforts to mitigate climate change. It鈥檚 a fair bet that much of what we do not yet know for sure will turn out to be scarier than most of us like to imagine.
鈥淚t鈥檚 a fair bet that much of what we do not yet know for sure will turn out to be scarier than most of us like to imagine鈥�
