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Friday, July 11, 2008
More Support for Lack of Aerosols Augmenting Recent Decadal Warming

By Joseph D’Aleo, CCM, AMS Fellow

Back in November 2007, we posted a story on how volcanism affected climate, - producing global cooling after major eruptions, and a warming after lengthy quiet volcanic periods.

See larger maps here.

In March, we published a story about a paper by David Shiga in the New Scientist Environment Journal that supported that notion based on brightness measurements during lunar eclipses. He showed brighter eclipses in the recent decade due to cleaner atmospheres.

Now a new story in the same journal Cleaner Skies Explain Surprise Rate of Warming, 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 (actually 19 years), 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.

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. Ironically the climate models assumed aerosols cooled the earth and created the cooling from the 1940s to 1970s. Now it appears that was wrong. The models only worked because they inserted and tweaked up the importance of the aerosol cooling in the middle of the last century. Modelers are not going to like this one. They may have to consider something radical like giving more credit to the sun or oceans.

In prior decades when pollution - particulates and hydrocarbon based haze and pollution were deemed a health problem and the goal was to develop clean burning engines and factories that only put out the natural gases - water vapor and carbon dioxide. Well we succeeded. That is until the greenhouse theory caught favor that said water vapor and carbon dioxode were bad for the planet and we have to stop at least the carbon part which was causing warming. Now suddenly much of the warming is due to the fact we cleaned up the atmosphere.  Seems like the protein vs carbs vs fats good versus bad arguments played put again this time in climate.

Posted on 07/11 at 12:42 AM
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