Global dimming: Clearer skies in Europe added to warming

Clearer skies in Europe added to warming

January 18th, 2009 in physorg.com

Sheep graze on a meadow near Munich as the sun sets. Fog, mist and haze in Europe have declined over the last three decades, a trend that may have stoked regional warming and ironically could be linked to better air quality, a study published on Sunday says.

Fog, mist and haze in Europe have declined over the last three decades, a trend that may have stoked regional warming and ironically could be linked to better air quality, a study published on Sunday says.

From 1978-2006, temperatures in parts of Europe rose above the global land average, with prominent increases in the north, centre and eastern parts of the continent.

As much as 20% of Europe's warming during this time, according to the study, can be pinned on a reduction in fog, mist and haze, which -- because they are white -- reflect solar radiation and thus keep the ground cool.

In eastern Europe, the decline in fog, mist and haze could account for 50%, the paper believes.

The authors, led by Robert Vautard of France's Atomic Energy Commission (CEA), pored over data from 342 weather stations around Europe.

They found that over nearly 30 years, the number of days categorised as having restricted visibility fell by half. These categories were determined by ranges of visibility at 2, 5, and 8 km (1.2, 3, and 5 miles, respectively).

The phenomenon is closely linked to falling levels of atmospheric sulphur dioxide (SO2), a byproduct of burning oil and coal that causes notorious "acid rain" that damages forests and lakes.

The temperature rise has been especially perceptible in Eastern Europe, where the end of the Communist system closed down innumerable sources of coal pollution.

However, the SO2 cleanup is now largely tapering off.

This means the fog reduction will probably stop and "the warming trend in Europe will not be so large in the coming years," Vautard told AFP.

According to the Intergovernmental Panel on Climate Change (IPCC) -- the UN's paramount authority on global warming -- the global average temperature rose 0.74 °C (1.33 °F) from 1906-2005, and the pace in the last 50 years was double that of the first half-century.

A blanket of fog can reduce local temperatures by some 2 °C (3.6 °F), according to figures quoted in the new study.

Link to article: http://www.physorg.com/news151522638.html