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redOrbit Staff & Wire Reports – Your Universe Online
Global warming was slowed between 2000 and 2010 because of sulfur dioxide spewed forth by volcanoes, researchers from the University of Colorado Boulder (CU-Boulder) and the National Oceanic and Atmospheric Administration (NOAA) claim in a new study.
Some experts had blamed China and India for the phenomenon, as both countries increased their industrial sulfur dioxide emissions by an estimated 60 percent during that decade. The new findings essentially exonerates those two Asian nations, lead author Ryan Neely of the Cooperative Institute for Research in Environmental Sciences (CIRES) said Friday in a statement.
Writing in the online edition of the journal Geophysical Research Letters, Neely and his colleagues report that increases in stratospheric aerosols over the past 13 years have counteracted nearly one-fourth of the temperature increased that have been blamed on human greenhouse gas emissions.
Portions of sulfur dioxide emissions from the planet´s surface ultimately rise to as much as 20 miles into the stratosphere, where chemical reactions cause them to be changed into sulfuric acid and water that reflect sunlight back into space and keep the planet cool.
Neely and researchers from CU-Boulder, the NOAA, MIT, NASA’s Langley Research Center, and the National Center for Atmospheric Research (NCAR) reported that emissions caused by volcanoes of “small to moderate” size caused global warming to slow during that 10-year period.
The recently-published study was intended, at least in part, to resolve conflicting conclusions from a pair of previous studies seeking the origin of the stratospheric sulfur dioxide. A 2009 NOAA-led study suggested that India and China´s increasing emissions may have been to blame, while a 2011 Langley Research Center-led study pinpointed moderate-sized volcanic eruptions as at least playing a role in the increased particulate levels.
“The biggest implication here is that scientists need to pay more attention to small and moderate volcanic eruptions when trying to understand changes in Earth’s climate,” said co-author Brian Toon, a professor at the CU-Boulder Department of Atmospheric and Oceanic Sciences. “But overall these eruptions are not going to counter the greenhouse effect. 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.”
“This paper addresses a question of immediate relevance to our understanding of the human impact on climate,” added Neely, who emphasized that the decade-long study is inadequate to determine longer-term climate change trends worldwide. “It should interest those examining the sources of decadal climate variability, the global impact of local pollution and the role of volcanoes.”