Volcanic Eruptions Help Cause Global Warming 'Hiatus'

Ironically, the hottest spots on planet Earth are helping offset global warming.

According to a report from the Lawrence Livermore National Laboratory, volcanic eruptions early in the 21st century have partially offset global warming caused by the emission of greenhouse gases.

While there have been increasing levels of atmospheric greenhouse gases and an increase in the heat of the ocean, global temperatures in the troposphere have shown little warming. Volcanic eruptions have contributed to this, a finding described in a new study appearing in the Feb. 23 issue of Nature Geoscience journal.

The study explains that volcanic eruptions bring sulfur dioxide into the atmosphere, and if the eruptions are strong enough to force gas beyond the troposphere and into the stratosphere, the gas forms sulfuric acid droplets, which are also called "volcanic aerosols." The drops reflect incoming sunlight back into space, which cools the lower atmosphere and the Earth's surface.

"In the last decade, the amount of volcanic aerosol in the stratosphere has increased, so more sunlight is being reflected back into space," said Lawrence Livermore climate scientist Benjamin Santer. "This has created a natural cooling of the planet and has partly offset the increase in surface and atmospheric temperatures due to human influence."

Human-caused atmospheric greenhouse emissions have increased from 2000 to 2012, which usually causes the troposphere to warm, and the stratosphere to cool. Volcanic eruptions have been causing the opposite to happen, which has led to what is being called a "warming hiatus."

Researchers conducted two tests to see if volcanic eruptions have had cooling effects. Researchers found significant correlations between volcanic aerosol observations and lower tropospheric temperatures, as well as sunlight reflected back into space by the aerosol droplets.

Researchers at San Diego State University assert that the role humans play in global climate change may be less important than the impact posed by natural processes, such as volcanic eruptions. Volcanic eruptions also contribute to ozone depletion, as well as to the warming and cooling of the earth's atmosphere.