Humans 'affect global rainfall'

Human-induced climate change has affected global rainfall patterns over the 20th Century, a study suggests.

Researchers said changes to the climate had led to an increase in annual average rainfall in the mid-latitudes of the Northern Hemisphere.

But while Canada, Russia and northern Europe had become wetter, India and parts of Africa had become drier, the team of scientists added.

The findings will be published in the scientific journal Nature on Thursday.

Climate models have, for a number of years, suggested that human activity has led to changes to the distribution of rain and snow across the globe.

However, the computer models have been unable to pinpoint the extent of our influence, partly because drying in some regions have cancelled out moistening in others.

Making the link

The scientists from Canada, Japan, the UK and US used the patterns of the changes in different latitude bands instead of the global average.
They compared monthly precipitation observations from 1925-1999 to those generated by complex computer models to see if they could identify if human activity was affecting rainfall patterns.

"We show that anthropogenic forcing has had a detectable influence on observed changes in average precipitation within latitudinal bands," the researchers wrote in the paper.

"These changes cannot be explained by internal climate variability or natural forcing."

The team estimated that human activity, such as burning fossil fuels, was likely to have led to a 62mm increase in the annual precipitation trend over the past century over land areas located 40-70 degrees north, which includes Canada, northern Europe and Russia.
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