Climate change 'triggering increased rainfall'

Rainfall has increased both north and south of the equator

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Monday, 23, Jul 2007 06:04

Scientists have found for the first time that human-induced climate change has triggered significant shifts in precipitation such as increased rain and snowfall either side of the equator.

Previous studies have already linked global warming to changes in surface air temperature and rising sea levels and temperatures.

The latest finding is based on international research which studied the link between human actions and precipitation (any product of atmospheric vapour).

Researchers from Environment Canada and six research centres in the UK, Japan and US charted changes in greenhouse gases (GHG) and sulphate aerosol concentrations in the atmosphere along with global precipitation during the past century.

GHG and sulphate aerosols are produced primarily by burning fossil fuels.

Most of the increased precipitation was found to take place 50 degrees north of the equator in areas including Canada, Europe and Russia as well as in the southern hemisphere.

Drying on the other hand increased in a region north of the equator including Mexico, Central America and northern Africa.

Writing in the journal Nature, the scientists warn that these changes in precipitation may already have had a negative effect throughout the world.

"We estimate that anthropogenic forcing [man-made effects] 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," the researchers write.

"The observed changes, which are larger than estimated from model simulations, 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 [region in northern Africa]."