A good Economist piece on global warming.

The George Will “global warming has ended” moment shows up as that little dip towards the end, before it returns to trend. So, what effect will the new data have on that meme? Quite possibly none. People who tried to cast doubt on global warming in 2009 based on a few years one could isolate so that they didn’t show a discernible trend will now no doubt respond that a couple of very hot years don’t prove anything. Which underlines how often the conclusions one draws from data are determined by a combination of the hypotheses you’re framing, and at what point you start looking.

The first time we heard a scientist authoritatively state that the evidence was in, and that global warming was real, was when James Hansen said it while presenting his research to Congress in 1988. That was a daring claim for Mr Hansen to make at that point. It was daring because it was very clearly falsifiable. If, after 1988, global temperatures had stopped rising, or had started to exhibit a lot of volatility—if there had been a decade-long cooling episode, such as the world saw in the late 1930s and 40s—then Mr Hansen would have been discredited. But that didn’t happen. Instead, for a decade and a half after Mr Hansen made the call, global mean temperatures kept going up and up. They bounced around a bit in the mid-2000s, and have now resumed rising again.