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Human-induced climate change causes shifts in rainfall
mongabay.com
July 23, 2007


Human-induced climate change has caused changes in rainfall patterns around the world over the past century, claims a new study published in Nature.

Using fourteen climate models to compare observed changes in land precipitation during the twentieth century, an international team by researchers from Environment Canada show that humans have had "a detectable influence on observed changes in average precipitation" and that the changes "cannot be explained" by natural causes.

"For the first time, climate scientists have clearly detected the human fingerprint on changing global precipitation patterns over the past century," said Environment Canada in a statement.

The researchers write that humans have "contributed significantly to observed increases in precipitation in the Northern Hemisphere mid-latitudes, drying in the Northern Hemisphere subtropics and tropics, and moistening in the Southern Hemisphere subtropics and deep tropics."

They add that observed changes are larger than those projected from model simulations and "may have already had significant effects on ecosystems, agriculture and human health in regions that are sensitive to changes in precipitation, such as the Sahel" of Africa.

The study comes as flooding in Britain, China, and Texas has killed scores of people.

The scientists say the research is the first to show that global warming is causing global precipitation to increase. Previous studies were inconclusive since changes in rainfall in different parts of the world tend to "cancel each other out and thereby reduce the strength of the global average signal."

Xuebin Zhang, Francis W. Zwiers, Gabriele C. Hegerl, F. Hugo Lambert, Nathan P. Gillett, Susan Solomon, Peter A. Stott & Toru Nozawa (2007). Detection of human influence on twentieth-century precipitation trends. Nature advance online publication 23 July 2007 | doi:10.1038/nature06025

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