Ice cores reveal 2.5 degree Celsius increase in 150 years

Brussels, 20 Feb 2006

Ice cores drilled in Siberia from the Belukha glacier by a joint Swiss-Russian team have revealed increases in temperature of 2.5 degrees Celsius over the past 150 years. The cores have also shown that air pollutants have increased since 1940, when heavy industry began in Siberia.

The team, led by the Swiss Paul Scherrer Institute, drilled the cores at a height of around 4,000 metres, in the shadow of the 4,506 metre high Belukha, the highest peak in central Asia. The 86 metre-long cores from the glacier were taken back to Switzerland for analysis.

The team also observed the build-up of pollutants in the ice, corresponding to the march of industrialisation in this remote area, bordering Mongolia, Kazakhstan, Russia and China.

The team tested for temperature differences by looking at the depletion of oxygen-18 isotopes in the ice. These isotopes have a relationship to temperature, and stabilise as ice freezes. As glaciers build up in layers, in a similar way to rings on a tree, it is possible to date the layers extremely accurately and gauge what the temperature was when the ice froze.

The report, published in the Journal of Geophysical Research, says that 'the two temperature proxies indicate a strong warming trend in the order of between 1.6 and 0.4 degrees Celsius and 1.7 and 1.1 degrees Celsius over the last century, inferred from melt percentages and the oxygen-18 record. Since the mid-19th century, the oxygen-18 record indicates a warming trend of around 2.5 to 1.7 degrees Celsius.'

The average temperature increase globally for the same time period is 0.9 degrees Celsius. The Siberian temperature increase is almost three times this figure, and the team initially speculated that this could be due to the passing of the so-called Little Ice Age. However, the team concluded that the rise in temperature is more likely, and more worryingly, due to the continental climate of the area.

Climate change models predict an increase in extremes of weather, and this effect is amplified for areas with a continental climate. In fact, the situation has worsened since 1988, as patterns visible in the snow which correspond to melted and re-frozen ice attest. 'The sudden onset of large melt features since 1988 indicates that the upper reaches of Belukha glacier are experiencing a change from the recrystallization to the cold-infiltration zone that now allows for multiannual percolation of meltwater, implying that the conservation of accumulation and geochemical properties, including those providing temperature proxies, is currently endangered,' reads the paper.

This stark finding contrasts with the paradoxical discovery that pollutants in the ice have actually decreased since the early 1980s, which implies that the maximum industrial output had already been reached - some ten years before the break-up of the Soviet Union.

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CORDIS RTD-NEWS/© European Communities, 2005
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