Tonga volcano eruption likely not large enough to affect global climate, experts say

By Rachel Ramirez and Brandon Miller, CNN

Though massive volcanoes have the potential to affect global temperatures and weather, the eruption near Tonga on Saturday was likely not large enough to impact global climate, experts tell CNN.

The Hunga-Tonga-Hunga-Ha’apai eruption on Saturday was enormous; likely the largest in 30 years, according to experts. It injected a huge cloud of ash and sulfur dioxide, or SO2, high into the atmosphere, more than 30 kilometers (around 19 miles) above sea level, according to data from NASA satellites.

At that height, above the influence of the jet stream in a layer of atmosphere known as the stratosphere, aerosols can remain for years. Importantly, when SO2 reaches the stratosphere, it reacts with water and creates a hazy layer of gas that prevents sunlight from reaching the Earth’s surface and can lead to cooler temperatures.

But scientists have also estimated from satellite data the total SO2 mass from the Saturday eruption was 0.4 teragrams — 400 million kilograms — of SO2, which is well below what scientists say could significantly alter global climate.

For instance, the Mount Pinatubo eruption in 1991 released 15 to 20 teragrams of SO2 high into the atmosphere, resulting in a 0.6 degree Celsius (1 degree Fahrenheit) drop in global temperature over the next 15 months, according to NASA.

Erik Klemetti, associate professor of Geosciences at Denison University in Granville, Ohio, said the sulfur dioxide spewed into the atmosphere by the Hunga Tonga eruption was “well below the usual threshold for anything that’s going to have any significant impact on climate in general.”

Klemetti’s assessment was echoed by other scientists on Twitter.

“If the volcano decides that it’s going to do a number of explosions, and keeps on adding, that’ll change things,” Klemetti told CNN. “But right now, it seems like it was a short enough event that didn’t have enough sulfur in it to likely cause much of a climate impact.”

Klemetti noted the Tonga eruption might have a regional impact on temperature, though scientists are still unsure of how significant it could be. Klemetti noted it ultimately depends on how much of the SO2 made it into the stratosphere.

Klemetti also emphasized it is not the ash which affects global temperature and weather. He said most people assume volcanic ash is what’s reflecting sunlight and affecting global temperature, but unlike aerosols, ash doesn’t linger in the atmosphere for very long. Instead, there needs to be a significant amount of sulfur dioxide.

An ash particle is an “actual physical shard of glass,” he said. “They’re tiny, but they have enough mass that they’ll fall out of the atmosphere fairly quickly.”

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