Scientific Reports has published a study from a team of researchers from Michigan Technological University that outlined a worldwide inventory for volcanic sulfur dioxide emissions. The last previous record of this information was published in the 1990s and was based on fewer volcanoes and from ground readings only. Conversely, in this recent study, scientists used data from the Dutch-Finnish Ozone Monitoring Instrument on NASA's Earth Observing System Aura satellite, collecting emissions from 2005 to 2015 of 91 unique volcanoes.
Results from the analysis found that volcanoes collectively emit 20 to 25 million tons of sulfur dioxide into the atmosphere annually.
"Many people may not realize that volcanoes are continuously releasing quite large amounts of gas, and may do so for decades or even centuries," says volcanologist Simon Carn, an associate professor at Michigan Tech in Houghton, Michigan, and the lead author of the new study. "Because the daily emissions are smaller than a big eruption, the effect of a single plume may not seem noticeable, but the cumulative effect of all volcanoes can be significant. In fact, on average, volcanoes release most of their gas when they're not erupting."
The data is important because it will help understand climate and atmospheric chemistry models and provide more insight into human and environmental health risks, reports NASA. Sulfur dioxide plumes have caused health concerns in communities like Kilauea in Hawaii land Popocatepetl in Mexico where volcanoes are constantly emitting gases that concert into sulfate aerosols, which are hard to breathe. Sulfur dioxide, another product of these volcano emissions, also causes acid rain and can irritate people’s skin and lungs.
In order to understand the current levels of atmospheric sulfur dioxide though, scientists must also measure the volcano emissions against those from anthropogenic pollution. Human activities emit about two times as much sulfur dioxide into the atmosphere as the sum of emissions from the volcanoes in the study, according to co-author Vitali Fioletov, an scientist at Toronto's Environment and Climate Change Canada. ScienceDaily reports that Fioletov was involved in analyzing and recording sulfur dioxide emissions sources from human activities and volcanoes and he was able to trace emissions derived from the satellite observations back to their source by using wind data.
Nevertheless, because of stricter regulations on power plants (at least before the EPA was run by a man who has declared that carbon dioxide is not a cause of climate change), human emissions have been declining in many countries. This means that understanding the full picture of how persistent volcanic emissions affect sulfur dioxide levels is even more imperative to designing the path forward.
In the following clip, you can see the emissions coming from Japan's Nishinoshima Volcano.