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Wednesday, January 28, 2004

Last Summer's European Heat Wave and Why Global Warming Might Not Be the Big Problem -  

Last summer was one of the hottest in Europe in recent memory (about six degrees hotter than the average from 1960-1990) and the heat had all sorts of consequences -- not the least among which were the deaths of thousands of French citizens (mostly elderly). One school of thought might suggest that this heatwave is an inevitable consequence of global warming: that with globally averaged warming we should expect to see, you know, warm weather.

Christoph Schar and others claim this just isn't true. They argue that, even if you account for the general warming trend, you can only explain last summer's heat wave if the climate system is getting more variable while it warms m(see Reuter's story here . The paper is available here (it unfortunately requires a subscription to the journal Nature)).

So why is this important? While global warming gets alot of the press its important to remember that it's always globally averaged warming. Clearly humans don't live in a globally averaged world (perhaps unless your a business type who spends all his time travelling - in which case you probably principally experience the climate of office buildings/airplanes) so what we'd really like to know is what happens to local climate while the globe is warming. Schar's paper argues that what's happening to the climate now, and what will likely happen to the climate increasingly often in the future, is an increase in variability: on average warmer but a substantial increase in both really hot and really cool days. If this is true it has critical consequences. If you're a retailer trying to predict what sort of clothes you will stock for the winter clearly you'd like to have some sense of whether the winter will be blamy or bitterly cold. If you sell heating oil you may go bankrupt if you guess wrong and purchase a lot of oil during a particularly warm year. If you're a farmer, clearly a climate that oscillates substantially from year to year makes it much more difficult to decide what would be appropriate to plant. The list goes on, but you get the idea. Even though the U.S. economy isn't agrarian climate influences it in all sorts of ways. And mostly what's bad are the same sorts of events Schar thinks are already happening: strong year to year variability.

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