A new study in the journal Nature Communications has revealed that volcanic eruptions may be behind global warming slowing down in spite of rising greenhouse gas levels over the past decade. After taking the lower regions of the earth’s atmosphere into consideration, the data showed that aerosol released by volcanoes reflected twice as much solar radiation during the years 2008 to 2011.
Scientists previously knew aerosol created a cooling effect, but underestimated the impact it could have in the tropopause, the transition layer between the troposphere (where we live) and the stratosphere (where planes fly). The research was led by the University of Lund, who found the periods when these particulates increased coincided with times the average surface temperature did not rise.
The years from 2005 to 2012 stand out in that regard. Three eruptions in particular occurred in that period; the Kasatochi in 2008, the Sarychev in 2009 and the Nabro in 2011. Each injected one megaton of sulfur dioxide into the atmosphere. The report also indicates there are several other factors other than the amount to determine whether a volcanic eruption will have an effect on the atmosphere.
One is the injection height. Another is the latitude the eruption occurs in. Since the air flow between the northern and southern hemisphere is largely disconnected, an explosion in the equatorial region would have maximum impact. The season is also a factor, with an eruption having the most impact if it occurs in late summer when the solar radiation is still strong.
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Nature hasn’t solved the global warming problem though. The report cautions that it’s still happening since this is a temporary phenomenon. Greenhouse gases will continue to accumulate and increase global temperature levels gradually.