Thursday, March 31, 2011

Climate modeling and the rain

Terra Daily: Extreme precipitation events seem to be becoming more common in the Northern Hemisphere. But it's been very hard for scientists to pinpoint a major weather event to global warming. Still, when a 100-year flood comes and then returns in a matter of a few years, it's hard not to consider it a sign of a warming world.

Several papers published in the journal Nature demonstrate that such extreme precipitation events in specific localities is the result of climate change and not an overactive imagination. The scientists studied the actual, observable precipitation patterns in the 20th century and then compared them to climate model simulations and a splash of probability to discover a close, predictive match up.

They claim that their results provide "first formal identification of a human contribution to the observed intensification of extreme precipitation." The scientists, led by Seung-Ki Min at the Climate Research Division from Environment Canada in Toronto, say that the global climate models may, in fact, be underestimating the amount of extreme weather events, "which implies that extreme precipitation events may strengthen more quickly in the future than projected and that they may have more severe impacts than estimated."

In another study, this one led by Pardeep Pall at the University of Oxford, looked at a specific weather event: the 2000 floods in England and Wales, which occurred during the wettest autumn since 1766. About 10,000 properties were flooded over, causing evacuations, disruptions in rail service and power supplies, and an economic dent of about a Pounds 1 billion.

Oxford scientists used a climate model and simulated different scenarios of rainfall patterns based on greenhouse gas levels in the atmosphere. The results were fed into a model that simulated severe river runoff and found that in nine out of 10 cases, the model forecast an increased risk of floods when 20th century levels greenhouse gases were included…

A downpour in Toronto, shot by ?? ?, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license

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