New research shows that comparatively tiny volcanic eruptions can raise aerosol particles in the atmosphere, temporarily mitigating the worldwide warming brought on by greenhouse gases. The impact of such smaller sized eruptions has been underestimated in climate models, the researchers say, and helps to account for a discrepancy among these models and the actual temperatures observed more than the last 15 years.
The findings are reported in a paper in the journal Geophysical Overview Letters, co-authored by MIT Professor Susan Solomon, postdoc David Ridley, and 15 other people. They aid to clarify the apparent slowdown in the pace of global warming recorded over the final ten to 15 years—possibly explaining as much as half of that slowdown, the researchers say.
"We've learned a lot of new issues about how the Earth's climate alterations, not just from year to year but from decade to decade, as a result of current analysis," says Solomon, the Ellen Swallow Richards Professor of Atmospheric Chemistry and Climate Science at MIT. "Numerous independent sets of observations show that somewhat modest volcanic eruptions are vital."
For the last quite a few years, "It's been quite clear that the observed trends are not following what the models say," Ridley adds: Whilst the overall warming trend continues, its price is slower than projected. Earlier study has suggested that some of that discrepancy can be accounted for by an raise in the amount of warm water being carried down to the deep ocean, but other processes can also contribute.
The cooling impact of big volcanic eruptions, such as that of Mount Pinatubo in the Philippines in 1991, was currently widely recognized the new work shows that smaller eruptions can have a considerable cooling impact as nicely, and offers a greater estimate of how a great deal of the recent reduction in warming could be explained by such eruptions: about 30 to 50 % of the discrepancy, the team identified.
The group located that modest eruptions make a considerable amount of aerosol particles, which reflect sunlight, in a area of the upper atmosphere that is comparatively poorly monitored: Satellites can provide very good information about the atmosphere down to around 15 kilometers above ground level, beneath which clouds interfere. The group filled in the missing region employing numerous balloon, laser radar (lidar), and ground-based measurements.
Aerosols in that intermediate zone, from about a dozen modest eruptions about the globe through the last 15 years, may perhaps double preceding estimates of the cooling impact of eruptions, Ridley says.
"It really is often thrilling in science when you can come across a number of measurements that lead to a popular conclusion," Solomon adds. "Various independent sets of observations now show that somewhat modest volcanic eruptions are a lot more essential for international climate than previously believed."
All round, these smaller eruptions have lowered the raise of worldwide temperature given that 2000 by .05 to .12 degrees Celsius, counteracting some of the warming that would otherwise have occurred. Now, using this new facts, groups that carry out climate modeling can update their models to more accurately project global climate alter more than the coming decades, Ridley says.
Alan Robock, a professor of environmental sciences at Rutgers University, says, "This operate helps to improved quantify the impacts of the most critical all-natural bring about of climate adjust, volcanic eruptions. We have an imperfect observational system for volcanic aerosols, and this operate exploits some previously unused sources of facts to better quantify the effects of modest eruptions for the past decade."
Robock, who was not involved in this analysis, adds that in light of these findings, "We require a far more robust observing program for volcanic aerosols, to do a better job of measuring future tiny eruptions."
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