20. May 2006

2.5 degrees warmer in the last 150 years

Noticeable temperature increase in the Siberian Altai

An ice-core from a Siberian glacier evidences a much higher than average climate change in this central Asian mountain region. A Swiss/Russian research team, under the leadership of the Paul Scherrer Institute (PSI), extracted an ice-core from the Belukha glacier and then analysed this frozen climate archive. In addition to the temperature change they were able to show that concentrations of pollutants had risen since the 1940s, when industrial activities in Siberia increased.

At 4506m the Belukha is the highest peak in the central asian area of the Siberian Altai, where four countries, Kazakhstan, Russia, China and Mongolia meet. Due to its site at over 4000m the Belukha glacier is an excellent climate and environment archive. The research team drilled 139 metres into the glacier and extracted an ice-core which was transported to Switzerland for analysis.

The mountainous region of Altai has a continental climate which is distinctive for its extreme temperature variations, both daily and annual. Continental climates are suspected of being particularly susceptible to warming due to greenhouse gases. This area is extremely polluted from mining and heavy industry in east Kazakhstan and west Siberia. Both warming and pollution were confirmed by the analysis of the ice-core.

Visible rise in temperature

The ratio of stable oxygen isotopes in the ice reflects the temperature at precipitation formation and shows an increase of 2.5 degrees over the past 150 years. This is nearly three times more than the average increase of 0.9 degrees in the northern hemisphere. The marked change in temperature is also directly visible in the ice-core, shown by the increase in layers which have melted and re-frozen. Such layers are formed when the air temperature is over zero and the snow on the surface of the glacier begins to melt. The melt water percolates into the snow and upon re-freezing forms a transparent layer, in contrast to the normal air bubble-filled glacial ice. Such melting processes have occurred more frequently in the last ten years, affecting the quality of the archive – a common threat to high mountain glaciers.

Astounding reduction in pollution

The temporal evolution of air pollutants, such as sulphate and lead from heavy industry and nitrate from traffic which were found in the Belukha glacier, can be easily distinguished from pollutants in Alpine glaciers. Generally higher levels are found from the 1940s onwards, corresponding to increases in population and industrial activity in Siberia. Surprisingly the concentration of pollutants becomes weaker as early as the 1980s, and not in 1991, with the break-up of the Soviet Union. This implies that the maximum industrial output had already been reached long before Perestroika and the new soviet political system.