Sunday, July 01, 2012

Bad Weather

The old story about the frog allowing himself to be cooked when the temperature of the water he's in is raised slowly enough is apocryphal, but the notion isn't crazy, at least when applied to humans. We tend not to notice gradual changes. That's especially true when the relevant changes take place over generations. That's one reason the story of human induced (anthropogenic) global warming (AGW) has trouble maintaining traction.

Extreme weather events tend to get attention, though. This Summer in the US we have had the massive fire events in the West and the big 29-30 June derecho event in the Midwest and Mid-Atlantic. Both have occurred in the context of record heat. Are these the signature of AGW?

As usual, the considered scientific answer is maybe. We have had bad fire seasons before, and we have had severe derecho events before. The pattern of Western drought and intense heat we have seen is a prediction of global warming models, as is the kind of derecho spawning dynamics we have seen in the Midwest and East. If those models are believed, such weather seems certain to become more common. For right now, though, they are just small pieces of a pattern of circumstantial evidence.