Levels of greenhouse gases in the atmosphere have consistently risen over the last 10 years, but global surface temperatures did not follow the same trend. In a study published in the journal Nature Communications, researchers point to volcanic eruptions as a possible reason why global warming has slowed down.
Headed by the University of Lund, Sweden, researchers from the Max Planck Institute for Chemistry, the Karlsruhe Institute of Technology and the Leibniz Institute for Tropospheric Research, teamed up to gather atmospheric information to try and explain the pause in global warming recorded over the last decade. Based on results, the cooling effect volcanic eruptions offered was underestimated in climate models, especially those used in the most recent report released by the Intergovernmental Panel on Climate Change.
However, the researchers also pointed out that the cooling effect is only temporary, with the temperature of the Earth's surface once again rising because levels of greenhouse gases in the atmosphere continue to increase.
Data for the study was gathered through observations from the Cloud-Aerosol Lidar and Pathfinder Satellite Observation mission and in situ measurements and sampling made by IAGOS-CARIBIC observatory. Collected particles were analyzed with an ion beam accelerator at the University of Lund, Sweden to determine concentration levels.
"The ratio of particulate sulfur to ozone ... clearly demonstrates the strong influence from volcanism on the tropopause region," explained Sandra Andersson and Bengt Martinsson, lead authors for the study.
The tropopause is a transition layer between the troposphere and the stratosphere. An increase in volcanic aerosol particles in the region coincided with times that average surface temperature did not increase.
In particular, observations on volcanic aerosol particles showed levels were more prominent from 2005 to 2012. During this period, the Kasatochi erupted in the United States in 2008, the Sarychev in Russia in 2009 and the Nabro in Eritrea in 2011. Each of these eruptions deposited over one megaton of sulfur dioxide in the atmosphere.
However, while the amount of volcanic sulfur dioxide is a major component, injection height (or the height at which the volcano shot out the compound) is also a big factor, according to researchers, in determining if a volcanic eruption can contribute to slowing down global warming.
The study received funding support from the German Research Foundation and the German Federal Ministry of Education and Research. Jean-Paul Vernier, Andreas Zahn, Johan Friberg, Peter van Velthoven, Carl Brenninkmeijer and Markus Hermann also contributed to the study.
Photo: U.S. Geological Survey | Flickr
