Volcanoes Behind Earth's Cooling; China and India Exonerated

First Posted: Mar 01, 2013 09:19 PM EST

Volcanoes have more impact on earth’s climate than previously thought, scientists at the University of Colorado have found.

The researchers came across the finding as they looked for reasons our planet has not heated up as much as expected. The mainstream explanation was that the development in Asia (China and India, essentially) – where the industrial sulfur dioxide emissions increased 60 percent from 2000 to 2010, mainly driven by coal burning – was behind the cooling of Earth. According to the study by Ryan Neely which helped cement the mainstream view, small amounts of sulfur dioxide emissions from Earth's surface rise 12 to 20 miles into the stratospheric aerosol layer of the atmosphere, where chemical reactions create sulfuric acid and water particles that reflect sunlight back to space - which in turn cool the planet.

Neely said previous observations suggested increases in stratospheric aerosols since 2000 counterbalanced as much as 25 percent of the warming that scientists ascribe to human greenhouse gas emissions.

However, this new study by scientists at the University of Colorado points out that the new data on the issue, "essentially exonerate Asia, including India and China," from any blame for the latest cooling trend.

In other words, this new study "points the finger at emissions from small to moderate volcanoes as the culprit for the slowing in the warming of the planet," said Neely, a researcher at the Cooperative Institute for Research in Environmental Sciences, a joint venture of CU-Boulder and the National Oceanic and Atmospheric Administration.

The new project was undertaken in part to resolve the conflicting results of two other recent studies, one of which by a NOAA researcher pushed the hypothesis that aerosol levels in the stratosphere resulted from the sulfur dioxide emissions from Asia. A 2011 study led by Jean Paul Vernier from NASA's Langley Research Center in Hampton, Virginia, demonstrated even moderate volcanic eruptions play a role in increasing particulates in the stratosphere.

While both small and moderate volcanoes mask some of the human-caused warming of the planet, larger volcanoes can have a significantly larger effect, said Brian Toon of CU-Boulder's Department of Atmospheric and Oceanic Sciences. For instance, when Mount Pinatubo in the Philippines erupted in 1991, it expelled millions of tons of sulfur dioxide into the atmosphere --- and that ended up cooling the Earth slightly for the next several years.

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