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  Climate Hot Spot: Cleaner Air Means a Warmer Europe

Climate Hot Spot Cleaner Air Means a Warmer Europe

By Volker Mrasek

Part 2: "Our Findings Contradict the IPCC"

Sulfate particles not only minimize the transfer of solar radiation directly, they also encourage the accumulation of water droplets and clouds in the atmosphere -- which in turn creates a second, indirect form of radiation repellent, because the light-colored surface of clouds reflects sunlight. This is where it gets complicated, though. In the landmark report issued last year by the Intergovernmental Panel on Climate Change (IPCC), the United Nations organization stated that questions persist about the effect that sulfate aerosols have on the atmosphere.

"Our findings contradict the IPCC," said Rolf Philipona of MeteoSwiss, Switzerland's national weather service. He and his colleague Christian Ruckstuhl, who now works as a researcher in California, analyzed data from 25 weather stations in northern Germany and eight in Switzerland.

"We found that the increase in radiation on the ground is considerably greater under a cloudless sky than a clouded one," Philipona told SPIEGEL ONLINE. The direct impact of particulate pollution is about five times greater than the indirect impact, he explained. That shows, he claims, that sulfate aerosols play "a truly important, immediate roll" in Europe's climate conditions.

Geert Jan van Oldenborgh agrees. A physicist from the Royal Dutch Meteorological Institute (KNMI), van Oldenborgh sees a direct connection between cleaner air and climate change in Europe. But he does add a qualification: He says the aerosol effect is not notable year-round. It is only apparent in spring and summer, when days are long and solar radiation is naturally stronger. "But the temperatures in autumn and winter have also risen faster than expected," said van Oldenburgh. There must be another explanation for that phenomenon, he believes.

The Dutch weather institute recently conducted a study on the issue -- but the results have yet to be published, and researchers are currently unwilling to discuss preliminary findings. One can assume that changes in air currents during the cold months play a decisive roll. There is an increase in fronts from the West transporting warm air from the Atlantic; and at the same time the cold Siberian High is weakened.

Europe's air is not likely to get much cleaner than it is now -- neither in summer or in winter. "The concentration of aerosol is stabile," said ETH Zurich's Wild. And Philipona of the Swiss weather service, is sure that "this increase in temperature, as we saw in Europe in the 1980s, will not happen again."

But this is by no means an announcement that the danger has passed. Greenhouse gases are still represent a threat, and increasing and unchecked emissions will almost certainly warm the Earth's atmosphere. The German Meteorological Society (DMG) claims that the median temperature in Europe in 2040 will be 1.7 degrees Celsius higher than the median temperature before the Industrial Revolution. Frequent heat waves, severe storms and other extreme weather are a foregone conclusion.

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