I stumbled across this presentation given by Seinfeld in 2002.
MIT World: Aerosols and Climate

Has anyone been able to determine which scientific papers the media will report? It seems like a crap shoot to me. The latest is about aerosols and their effect on surface temperatures. The journal Geophysical Research Letters published a paper titled Aerosol and cloud effects on solar brightening and the recent rapid warming by a group of scientists mostly from Switzerland.

They found that the temperatures in Europe have been increasing faster than expected if greenhouse gases were the only cause. They also calculate that aerosols will cause a surface cooling. This is not news. The “surprising” part (their word) is that the cooling is mostly due to the direct aerosol effect and not the indirect cloud effect.
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I’m sure everyone is aware of the recent eruption of the Chaitén Volcano in southern Chile. There have been some pretty amazing photographs, satellite images, and videos. Besides the obvious negative effects to the local people, what other possible climate effects will this eruption have? We can use previous volcanic eruptions to learn what aspect of a volcanic eruption influences the global temperatures.

Solid, Liquid, or Gas?

Before the effects of a volcanic eruption can be determined, first we need to know what comes out of a volcano. The most obvious substance is the liquid hot magma (molten rock). In explosive volcanoes this is ejected into the atmosphere as tephra, which I think most of us would simply call “ash”.
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New Scientist had an article recently titled How cleaning up America dried up the Amazon by Mason Inman. It reported on a Nature paper by Cox et al., Increasing risk of Amazonian drought due to decreasing aerosol pollution. This paper shows that positive changes can have unintended consequences long distances from their source.

The gist is that the sulfates generated in the United States reflect incoming solar radiation. But the amount of these aerosols has been decreasing since the 1970s, when anti-pollution laws started restricting the amount of aerosols in the atmosphere. Since there are now less sulfates in the atmosphere, more radiation is being absorbed by the ocean near the United States. This change in where the radiation is absorbed may have changed the storm tracks in the North Atlantic, bringing them farther North. This has led to less rainfall in the Amazon rainforest.
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