By Leo Hickman
3 July 2012 Whenever an episode of extreme weather – heatwave, flood, drought, etc – hits the headlines, someone somewhere is sure to point the finger of blame at human-induced climate change. Such claims are normally slapped down with the much-aired mantra: “You cannot blame a single episode of bad weather on global warming.” But with the on-going record high temperatures affecting large parts of the US, there seems to be a noticeable reduction in such caveats and notes of caution. This week, scientists have been queuing up, it seems, to explain how the wildfires in Colorado, the heatwave across the eastern seaboard, and the “super derecho” are all indicative of “what global warming looks like“. Most pulled back, though, from directly blaming global warming for such weather events. “In the future you would expect larger, longer more intense heat waves and we’ve seen that in the last few summers,” Derek Arndt of NOAA Climate Monitoring told the Associated Press.” The same report added: “At least 15 climate scientists told the Associated Press that this long hot US summer is consistent with what is to be expected in global warming.” So, can we now say, or not, that specific extreme weather events are caused, or at least exacerbated, by global warming? Has anything changed in climate scientists’ understanding of the attribution – or “anthropogenic fingerprint” – of such events? Are they now more confident about making such links? I put this question to a number of climate scientists. […]

Is it now possible to blame extreme weather on global warming?