Thursday, July 10, 2008

Scientists find a cause of global warming: cleanliness

Environmental regulations have succeeded in reducing smog. Skies are cleaner now than even just a few decades ago. According to a new paper in Geophysical Research Letters, the cleaner air allows more sunlight to reach the Earth and this may be a major causes global warming. As reported by New Scientist:
GOODBYE air pollution and smoky chimneys, hello brighter days. That's been the trend in Europe for the past three decades - but unfortunately cleaning up the skies has allowed more of the sun's rays to pierce the atmosphere, contributing to at least half the warming that has occurred. ....

Christian Ruckstuhl of the Institute for Atmospheric and Climate Science in Switzerland and colleagues 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 per cent over the 29-year period, while solar radiation rose by around 1 watt per square metre (Geophysical Research Letters, DOI: 10.1029/2008GL034228). "The decrease in aerosols probably accounts for at least half of the warming over Europe in the last 30 years," says Rolf Philipona, a co-author of the study at MeteoSwiss, Switzerland's national weather service. [emphasis added]
If true, then numerical climate simulations, of which the UN is so fond, apparently have the whole aerosol issue backwards:
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.
Hat tip: Moonbattery.

PREVIOUSLY, I discussed here a paper which identified solar irradiation as a major influence on the environment and a paper which indicated that much of 'global warming' of terrestrial temperatures was likely due to experimental error. Many examples of the politicization of science by the left were discussed here. The emotional appeal of global warming to the left was discussed here.

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