Erupting volcanoes offset recent Earth warming, according to a team led by the University of Colorado at Boulder. Researchers arrived at this conclusion after searching for clues about why Earth did not warm as much as climatologists expected between 2000 and 2010.
Lead study author Ryan Neely said that the study’s findings take some of the pressure off of India and China, two countries that are believed to have increased their industrial sulfur dioxide emissions by approximately 60 percent from 2000 to 2010 through coal burning.
According to the United States Environmental Protection Agency, the biggest sources of sulfur dioxide emissions are from fossil fuel combustion at power plants (73 percent) and other industrial facilities (20 percent). Smaller sources of sulfur dioxide emissions include trains, large ships and some industrial processes. Sulfur dioxide emissions are associated with a number of negative effects on the respiratory system.
Neely, in a statement released by the university, noted that tiny amounts of sulfur dioxide emissions from Earth’s surface eventually rise 12 to 20 miles into the stratospheric aerosol layer of the atmosphere, where chemical reactions generate sulfuric acid and water particles that reflect sunlight away from the Earth and back to space.
The study’s findings reveal that it is emissions from small to moderate volcanoes that have been offsetting recent Earth warming, according to Neely, a researcher at the Cooperative Institute for Research in Environmental Sciences.
According to the U.S. Geological Survey, the effects of sulfur dioxide emissions on the environment depend on several factors, including the amount of gas a volcano emits into the atmosphere, whether the gas travels into the troposphere or stratosphere and the regional or global wind and weather pattern that moves the gas.
The motivation for the study was a desire to resolve conflicting results of two recent studies on the origins of the sulfur dioxide in the stratosphere. One study showed that aerosol increases in the stratosphere may have come from India and China’s rising sulfur dioxide emissions, while the other study revealed that moderate volcanic eruptions were to blame.