Cleaner skies means more global warming

London, July 10 : For past three decades, Europe has been following the trend of saying goodbye to air pollution and smoky chimneys but a new study has shown that cleaning up the skies has allowed more of the sun's rays to pierce the atmosphere, contributing to at least half the global warming that has occurred.

Average air temperatures in Europe have risen 1C since 1980, which is much more than expected from greenhouse-gas warming alone.

For the study, Christian Ruckstuhl of the Institute for Atmospheric and Climate Science in Switzerland and colleagues took aerosol concentrations from six locations in northern Europe, measured between 1986 and 2005, and compared them with solar-radiation measurements over the same period.

They found that aerosol concentrations dropped by up to 60 per cent over the 29-year period, while solar radiation rose by around 1 watt per square metre.

"The decrease in aerosols probably accounts for at least half of the warming over Europe in the last 30 years," New Scientist quoted Rolf Philipona, a co-author of the study at MeteoSwiss, Switzerland's national weather service, as saying.

The latest climate models are based on the assumption that aerosols have their biggest influence by seeding natural clouds, which reflect sunlight.

However, the researchers found that radiation dropped only slightly on cloudy days, suggesting that the main impact of aerosols is to block sunlight directly.

ANI