Volcanic eruptions mask global warming -- that's cool

Note that sulfur dioxide reacts with water to create acid. This results in acid rain, and would increase the acidification of the ocean caused by increased levels of the greenhouse gas carbon dioxide (CO2). Even with a couple of years of cooling caused by the eruption of sulfur dioxide, the 1990's decade was still warmer on average than the preceding decade, which itself was warmer on average, continuing a long term trend of global warming.

http://science.nbcnews.com/_news/2013/03/01/17150719-volcanic-eruptions-mask-global-warming-thats-cool?lite

by Megan Ganno
Mar. 1, 2013

Volcanic eruptions, even small and moderate ones, might counter some of the effects of global warming, new research suggests.

The planet didn't heat up as much as scientists expected it to from 2000 to 2010 (though it was still the warmest decade on record), and a new study finds that chemical compounds spewed during modest eruptions around the globe could be behind the trend.

When sulfur dioxide emitted by a volcano rises up to the stratospheric aerosol layer of the atmosphere, it undergoes chemical reactions, forming particles that reflect sunlight back into space instead of letting it get to the surface of the planet. This has a cooling effect on Earth that can help mitigate the impacts of heat-trapping greenhouse gasses.

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"Overall these eruptions are not going to counter the greenhouse effect," Toon said in a statement. "Emissions of volcanic gases go up and down, helping to cool or heat the planet, while greenhouse gas emissions from human activity just continue to go up."

Toon added that larger volcanoes can have a much bigger effect. For example, sulfur dioxide, a volcano in the Philippines that erupted in 1991, ejected so much sulfur dioxide into the stratosphere that the planet cooled by 1 degree Fahrenheit (0.55 degrees Celsius) and stayed slightly cooler for more than two years.

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