In response to their respective opinion articles, I argue that Kevin Trenberth's proposal to reverse the burden of proof in attribution studies is misguided, but Judith Curry's counter proposal to abandon hypothesis tests as useless is worse still. Some observed weather events will have been made more likely by human influence on climate, some less likely, and it is a legitimate and very important field of scientific enquiry to work out which are which. The appropriate null hypothesis to use in such studies is that human influence has not increased the probability of occurrence of a particular weather event unless the evidence suggests otherwise. WIREs Clim Change 2011, 2:931–934. doi: 10.1002/wcc.145
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