Volcanic Eruptions Can Cool Planet, But Hunga Tonga Likely Won’t, Scientists Say

Satellite imagery shows the Hunga Tonga-Hunga Ha'apai volcano
Satellite imagery shows the Hunga Tonga-Hunga Ha'apai volcano on Jan. 6, 2022, before the eruption on Jan. 14th , 2022 in Hunga Tonga-Hunga Ha'apai Islands, Tonga. Photo credit: Maxar via Getty Images

When the Hunga Tonga-Hunga Ha’apai volcano erupted on Saturday, it could be heard about 5,000 miles away in Alaska and produced an ash cloud the size of New England, The Washington Post reported. The volcano lies mostly underwater, about 20 miles southeast of Tonga’s Fonuafo’ou island in the South Pacific, reported CNN. It sits about 6,500 feet above the sea floor, but only about 328 feet can be seen above sea level.

When giant volcanoes erupt, they have the potential to affect temperatures and weather across the globe. According to CNN, the eruption of the Hunga Tonga-Hunga Ha’apai volcano was huge — likely the biggest recorded in 30 years, experts say — but it was probably not large enough to have an effect on the global climate.

“If the volcano decides that it’s going to do a number of explosions, and keeps on adding, that’ll change things,” associate professor of geosciences at Denison University, Erik 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 added that the Hunga Tonga-Hunga Ha’apai eruption could have an impact on the regional temperature, the significance of which would depend on how much sulfur dioxide (SO2) was in the stratosphere.

Ash RGB imagery shows the eruption using infrared channels to detect volcanic ash and sulfur dioxide gas. NOAA

The Hunga Tonga eruption spewed a cloud of SO2 and ash about 19 miles into the atmosphere, according to NASA satellite data, CNN reported. The atmospheric layer at that height is known as the stratosphere and, as it sits above the jet stream, aerosols can hang there for years. In the stratosphere, SO2 mixes with water to create a gas layer. The aerosols scatter sunlight and, as SO2 is reflective, cause some of it to be reflected away from Earth, according to Forbes. If there is sufficient SO2 to reflect enough light, it can cause cooler temperatures on Earth.

The SO2 from the eruption has been estimated by scientists to be 0.4 teragrams, or 400 million kilograms, according to satellite data, not nearly enough to have a significant impact on the world’s climate, reported CNN. The Mount Pinatubo eruption in the Philippines in 1991 — the largest volcanic eruption of the past 100 years, as the United States Geological Survey shows — produced 15 to 20 teragrams of SO2, which caused a 0.6 degree Celsius, or one degree Fahrenheit, decrease in global temperature for 15 months, according to NASA Earth Observatory.

A professor in the Department of Environmental Sciences at Rutgers, Alan Robock, said the Hunga Tonga-Hunga Ha’apai eruption will “produce about 1/50 of the impact of the 1991 Pinatubo eruption,” equal to an average of about 0.02 degrees, or 0.01 degree Celsius, of cooling, The Washington Post reported.

Michigan Tech professor Simon Carn said that to have a measurable effect on climate, the SO2 produced from Hunga Tonga would have to be five to ten times denser than it appeared to be.

“Only if the eruption injects a lot of SO2 into the stratosphere, at least 1000 [kilotons, or thousands of tons] or more, will there be a climate impact,” Robock wrote, as The Washington Post reported.

Experts say continued eruptions are something to monitor, according to The Washington Post.

“We have no way of knowing when this eruption will be over,” wrote Janine Krippner, a volcanologist at the Smithsonian Global Volcanism Program, The Washington Post reported.

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