Volcanoes Behind the Pause in Global Warming, Researchers Say

Recent volcanic eruptions might be linked with the "pause" in global warming, researchers have found.

During the 90s, there was a steady rise in surface temperatures with rise in greenhouse gases. They expected the warming to continue. However, research has shown that despite the rise of these heat-trapping gases, earth's surface temperatures have remained more or less constant in the past one and half decade.

Now, researchers at the Massachusetts Institute of Technology and colleagues show that this hiatus or pause in global warming can be explained by volcanic eruptions. Their study strengthens the idea that climate models need to account for volcanic eruptions.

"This is the most comprehensive observational evaluation of the role of volcanic activity on climate in the early part of the 21st century," says Susan Solomon, professor of Atmospheric Chemistry and Climate Science at MIT. "We assess the contributions of volcanoes on temperatures in the troposphere - the lowest layer of the atmosphere - and find they've certainly played some role in keeping the Earth cooler."

There are several factors that affect global warming- greenhouses gasses such as carbon dioxide and methane drive up surface temperatures while aerosols cool the planet. Volcanic eruptions can release fine particles in the air, which can lower surface temperatures.

Previously, University of Colorado Boulder researchers had shown that sulphur dioxide spewed by volcanoes could explain the difference between climate model predictions and observed data on global warming.

Seventeen small volcanic eruptions since 2000 pumped aerosols in the atmosphere, Livescience reported.  

The team used two different statistical tests to determine whether recent volcanic eruptions could explain the pause in global warming or if the hiatus was linked to some other natural phenomenon.

Researchers found a co-relation between volcanic eruptions and shifts in tropospheric temperature.

The study was funded by the U.S. Department of Energy and is published in the journal Nature Geoscience

"This paper reminds us that there are multiple causes of climate change, both natural and anthropogenic, and that we need to consider all of them when interpreting past climate and predicting future climate," said Alan Robock, a professor of environmental sciences at Rutgers University, according to a news release.  

Nearly 200 countries are expected to participate in a U.N. climate deal set to take place at a summit in Paris in late 2015, Reuters reported. Understanding the hiatus in global warming could help encourage countries to shift to renewable energy sources.