ST. LOUIS — There are few forces of nature capable of changing our planet and its climate as quickly and as dramatically as a volcano.  When they erupt, they hold the power to alter climate, weather and even global history.  That’s why scientists have been pouring over data following the eruption of Hunga Tonga Hunga in the Pacific Ocean in January.  They are looking for signs of change it may bring. 

Washington University professor of Earth and Planetary Sciences, Dr. Michael Wysession, says the affects from an eruption are different at different scales of time, and are very much dependent on the size of the eruption. 

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“On a very short-term basis, they inject material into the atmosphere that blocks out sunlight and has a cooling effect.  This material is a combination of ash and tiny droplets of sulfuric acid,” says Wysession.  “It’s like having a fuzzy translucent umbrella suddenly spread out across the globe.” 

The impacts change dramatically the further out in time you go. “On a long-term, the volcanic eruptions have a warming effect because one of the gases they emit is carbon dioxide, a greenhouse gas.  And so often when you look back in periods of earth’s history going back tens to hundreds of millions of years… times when the earth was unusually warm often correlate with times of intense volcanic activity.”   

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And the bigger and more violent the eruption, the more profound the effects.  “In 1980 Mount Saint Helens erupted about a cubic kilometer worth of volcanic ash and material into the atmosphere …two small really to have a noticeable effect on the climate.  In 1991 in the Philippines mount Pinatubo erupted, and that was about 10 km³ worth of volcanic material and that actually caused global temperatures to drop by about half a degree for a couple years,” says Dr. Wysession. 

So what have we learned about the effects of Hunga Tonga Hunga?  For starters, despite being 1/5th the size of Pinatubo, it ejected four times as much water vapor into the atmosphere because it is an underwater volcano.  That is a whopping 10% increase in the overall amount of water vapor in the atmosphere.  

That is a significant increase because water is a greenhouse gas.  So instead of blocking out the sunlight like normal volcanoes like a Pinatubo eruption… water vapor traps the heat from the sun as a greenhouse gas, and it will end up warming the planet according to Wysession.  And that warming can change a lot.  

“The jet stream patterns are sometimes changed because the amount of heating and where it occurs changes after one of these larger eruptions, so this is a whole new experiment basically the earth is providing for us and we’re just going to have to see how it plays out,” said Wysession.