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It looks dull, almost impenetrable in places. But if its findings are verified, it could turn out to be the most important scientific report published so far this year. In this month's edition of the Journal of Hydrometeorology is a paper written by scientists at the Met Office, which predicts future patterns of rainfall and evaporation.
Those who dispute that climate change is taking place, such as Melanie Phillips of the Daily Mail, like to point out that that the predicted effects of global warming rely on computer models, rather than "observable facts". That's the problem with the future - you can't observe it. But to have any hope of working out what might happen, you need a framework of understanding. It's either this or the uninformed guesswork that Phillips seems to prefer.
The models can be tested by means of what climate scientists call backcasting - seeing whether or not they would have predicted changes that have already taken place. The global climate model used by the Met Office still needs to be refined. While it tracks past temperature changes pretty closely, it does not accurately backcast the drought patterns in every region. But it correctly reproduces the total global water trends over the past 50 years. When the same model is used to forecast the pattern over the 21st century, it uncovers "a net overall global drying trend" if greenhouse gas emissions are moderate or high. "On a global basis, drought events are slightly more frequent and of much longer duration by the second half of the 21st century relative to the present day." In these dry, stodgy phrases, we find an account of almost unimaginable future misery.
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