Probably the only thing that has attracted more attention than the drastic increase in global temperature, is the surprising slow down of the increase in global temperature. Politicians take every opportunity to include it in their speeches, although they only wish to believe they have contributed to it with their new polices, but they cannot be sure.
Unfortunately for them, a team of scientists took on the job to find out who or what is the reason behind this unexpected change in trends and established that recent volcanic eruptions have caused the slow down.
The study appears in the latest issue of Nature Geoscience. The study was led by a team of researchers from the Lawrence Livermore National Laboratory, in collaboration with scientists from leading institutions such as the MIT, The Remote Sensing Systems, NASA’s Goddard Institute for Space Studies and the Canadian Centre for Climate Modeling and Analysis. The findings reveal that despite the steady increase in greenhouse gas emissions since year 2000, volcanic eruptions that took place in the beginning of the 21st century, released enough sulfur dioxide to be able to influence the global-mean temperatures.
Although there is no singe factor powerful enough to cause the slow-down, volcanic eruptions play a very significant role. The scientists explain that when significant quantities of the sulfur dioxide end up in the stratosphere, the part of the atmosphere where the ozone layer is, the molecules react with water to form small droplets of sulfuric acid, also referred to as volcanic aerosols. What makes these special is their ability to reflect a large portion of the UV light back to space, which consequently cools down the Earth surface. This is something that has been long overlooked when current climate models were developed.
This sounds like a reasonable explanation, and the scientists did provide evidence that volcanic activity has a lot to do with the unexpected slow-down. But it still remains questionable how much of sulfur oxide is needed to actually cause this change in trends, given that factors such as internal climate noise, or the very low and long minimum of the last solar cycle, are also held responsible. The main challenge to scientists now is to quantify the contributions of each of these factors and establish which one has the strongest influence.
Image (c) LLNL