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Last Updated: Friday, 10 August 2007, 09:27 GMT 10:27 UK
Soot 'influences Arctic climate'
Arctic ice  Image: BBC
Human activities have left a visible mark on the Arctic
Measurements from ice cores suggest that soot released by industrial activities has influenced climate change in the Arctic.

The researchers looked at ice cores covering the period 1788 to 2002.

The natural record shows that concentrations of black carbon, or soot, were particularly bad from 1851 to 1951, Science journal reports.

Soot adds to local climate warming because dark ground absorbs energy from the Sun that white snow would reflect.

Joe McConnell and Ross Edwards from the Desert Research Institute (DRI) in Reno, US, gathered and analysed ice core samples from various regions of Greenland.

These samples allowed them to analyse annual deposits of soot and other chemicals going back 215 years.

"In addition to black carbon, we measured a broad range of other chemicals at very high depth resolution in this same ice core," said Dr McConnell.

Vanillic ice

Among the other chemicals measured were vanillic acid and sulphur, two indicators of forest fire and industrial emissions, respectively.

"When we compare changes in the black carbon to changes in these other indicators, it is clear that most of the increases in black carbon in the late 19th and early 20th centuries, particularly in winter and spring, resulted from industrial emissions - probably from coal burning," he added.

Ice cores from before about 1850 show most soot came from forest fires. They found that the older soot samples contained vanillic acid, an indicator of burning conifer trees.

But since then, soot in the snow has increased several times over due mainly to industrial emissions.

Soot concentrations peaked in 1906-1910 and remained high for decades.

This decreased level of reflectivity, or albedo, allowed the surface to absorb more energy from the Sun.

These changes may have resulted in earlier snow melt and exposure of darker rocks, soil and sea ice, leading to warming throughout Greenland in the late 19th and early 20th Centuries when soot levels were at their highest.

"We used computer models to simulate the climate forcing impact of the observed changes in soot concentrations in Greenland snow during the past 215 years," said co-author Mark Flanner from the University of California.

Simulations were also used to extend the climate forcing results from central Greenland to the entire Arctic.

From these simulations, the average impact from soot pollution over the Arctic was about double that found for central Greenland.

In the peak period from 1906 to 1910, the warming effect of the industrial soot throughout the Arctic was estimated at eight times that during the pre-industrial period.

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