Thursday, August 26th 2010, 5:27 AM EDT
IT IS time to start asking the hard questions. Countless people in flood-stricken Pakistan have lost families and livelihoods. Who can they hold responsible and turn to for reparations?
Less than a decade ago, these questions would have been dismissed outright. "Many scientists at the time said that you can never blame an individual weather event on climate change," says Myles Allen of the University of Oxford. But a small meeting of scientists in Colorado last week - organised by the US National Oceanic and Atmospheric Administration, the UK Foreign and Commonwealth Office and the UK Met Office's Hadley Centre, among others - suggests the tide is turning.
The aim of the Attribution of Climate-Related Events workshop was to discuss what information is needed to determine the extent to which human-induced climate change can be blamed for extreme weather events - possibly even straight after they have happened.
Assigning blame in this way is not without precedent. In 2004, Allen and his colleagues showed to a high level of confidence that human greenhouse gas emissions had at least doubled the risk of the European heatwave of 2003 occurring.
Updated below with comments by Piers Corbyn
The basic idea in producing such a figure is straightforward. Run thousands of simulations of the climate as it is and as it would have been without human influences, then compare the number of times a given event occurs in each scenario. In 2004, technological limitations made it impossible to run simulations for long enough to reproduce the 2003 heatwave, so the analysis involved making certain assumptions.
"With the tools we have today we can do much better," says Allen. His team is now using borrowed computing space from thousands of PC owners to run simulations for recent devastating weather events, though their results are not yet in.
Kevin Trenberth of the National Center for Atmospheric Research in Boulder, Colorado, thinks similar analyses should be done within weeks of an event. For instance, we know that high sea-surface temperatures and large amounts of moist air over the Indian Ocean helped bring about the Pakistani floods and the heatwave in Russia. It should be possible to determine how great a role human climate change played in these events, Trenberth says.
"It should be possible to determine how great a role climate change played in the Pakistan floods"
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