Summer smog heats up the Arctic
The ground-level ozone formed by air pollution in the northern hemisphere is a key contributor to the warming of the northern polar region.
So far, according to Drew Shindell and her colleagues from Nasa's Goddard Institute for Space Research in New York, the triatomic oxygen compound has been considered a rather negligible quantity because, unlike CFCs, carbon dioxide or methane, it is very short-lived. However, a new study examining the relationship between ozone concentrations in the near-Earth troposphere and temperature changes over the last hundred years now comes to the opposite conclusion.
From their computer calculations, which were intended to determine the influence of individual greenhouse gases on certain regions of the earth, the researchers conclude that ozone has contributed between thirty and fifty percent to the observed strong warming of the North Pole. There is also a clear connection between rising temperatures and increasing ozone concentrations in the Arctic since 1950.
Most of the ozone-related warming there occurs during the winter and spring months. The gas is then transported northwards by the prevailing wind systems and is not broken down in the vicinity of its point of origin by photochemical and thermally triggered reactions. As the model also revealed, on the other hand, during the summer the ground-level ozone increases the heating up of other parts of North America, Europe and Asia, where most of the ozone, also known as summer smog, is produced anyway.
This result fuels fears that the Arctic is approaching a tipping point where the region's previously observed linear loss of sea ice could accelerate dramatically. According to Mark Serreze from the US National Snow and Ice Data Center in Boulder, the reason for this is the lack of regeneration of the pack ice in the Arctic this winter. For the second time in a row, less ice formed during the last polar night than thawed in the previous summer. As a result, the uncovered, dark sea area increases, the albedo decreases, and the warming also increases.