Cleaner Skies Speeding Global Warming
Since 1980, average air temperatures in Europe have risen 1°C: much more than expected from greenhouse-gas warming alone. Christian Ruckstuhl of the Institute for Atmospheric and Climate Science, Rolf Philipona, et al., took aerosol concentrations from six locations in northern Europe, measured between 1986 and 2005, and compared them with solar-radiation measurements over the same period. Aerosol concentrations dropped by up to 60% over the 29-year period, while solar radiation rose by around 1 watt per square metre (see “Aerosol and cloud effects on solar brightening and the recent rapid warming“). “The decrease in aerosols probably accounts for at least half of the warming over Europe in the last 30 years,” says Philipona.
The latest climate models are built on the assumption that aerosols have their biggest influence by seeding natural clouds, which reflect sunlight. However, the team found that radiation dropped only slightly on cloudy days, suggesting that the main impact of aerosols is to block sunlight directly.
“Cleaner skies explain surprise rate of warming,” New Scientist