 Katzav (2013b), however, considers another perspective on evidence—Mayo’s (1996) severe testing framework—and argues that the claim that more than half of the increase in global mean surface temperature since 1950 was due to anthropogenic forcing has not passed a severe test in Mayo’s sense, even when variety-of-evidence considerations are factored in; from a severe testing perspective, he contends, we still lack good evidence for this conclusion. He suggests that some weaker attribution claims—such as the claim that anthropogenic forcing had some role in post-1950 warming—might be ones for which there is good evidence in Mayo’s demanding sense. 