A new report in the journal Nature Geoscience says that the Earth's tropics are moving pole-wards much faster than previously believed, and have already expanded more than earlier studies had predicted for the entire 21st century.
While the idea has a visceral appeal - palm trees in Boston! - to climatologists, "tropics" are defined less by beach volleyball pits and more by the high altitude winds which determine climate in regions around the equator. Since shifts in these winds mean more warm, there could some relatively innocuous side-effects, like a longer growing season in parts of Canada. However, there's also a huge downside, including water shortages and desertification in temperate zones, as well as an upsurge in Jimmy Buffett songs on the radio.
Authors of the report say it's unclear what specific drivers are behind the tropical expansion, and make the dry but unsettling observation that "there is still much to be learned about this aspect of global climate change."
http://www.abc.net.au/science/articles/2007/12/03/2107763.htm?site=science&topic=latest
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