The eruption of an underwater volcano in Tonga was a “unique event” that could warm the Earth’s surface, scientists say

If an underwater volcano erupted in Tonga In January, its water explosion was huge and unusual – and scientists are still trying to understand its effects.

The volcano, known as Hunga Tonga-Hunga Ha’apai, shot millions of tons of water vapor high into the atmosphere, according to a study published Thursday in the journal Science.

Researchers estimate the eruption that dwarfs the power of the Hiroshima atomic bombincreased the amount of water in the stratosphere — the second layer of the atmosphere, above where humans live and breathe — by about 5%.

Now scientists are trying to figure out how all that water could affect the atmosphere and if it could warm the Earth’s surface in the years to come.

“This was a unique event,” said lead author Holger Voemel, a scientist at the National Center for Atmospheric Research in Colorado.

Large eruptions usually cool the planet. Most volcanoes emit large amounts of sulfur, which blocks the sun’s rays, explained Matthew Toohey, a climate scientist at the University of Saskatchewan who was not involved in the study.

The Tongan blast was much wetter: the eruption started under the ocean, so it shot up a cloud with much more water than usual. And since water vapor acts as a heat-trapping greenhouse gas, the eruption will likely increase temperatures rather than lower them, Toohey said.

It’s unclear how much warming is ahead.

Karen Rosenlof, a climate scientist with the National Oceanic and Atmospheric Administration who was not involved in the study, said she expects minimal and temporary impacts.

“This surge could warm the surface slightly for a short time,” Rosenlof said in an email.

In August, scientists said it had broken “all records” for injecting water vapor since satellites began recording such data — enough water vapor to fill 58,000 Olympic-size swimming pools.

The water vapor will linger in the upper atmosphere for a few years before making its way to the lower atmosphere, Toohey said. Meanwhile, the extra water could also accelerate atmospheric ozone depletion, Rosenlof added.

But it’s hard for scientists to say for sure because they’ve never seen an eruption like this one.

The stratosphere extends from about 7.5 miles to 31 miles above Earth and is typically very dry, Voemel explained.

Voemel’s team estimated the volcano’s plume using a network of instruments suspended from weather balloons. Typically, these tools can’t even measure water levels in the stratosphere because the amounts are so small, Voemel said.

Another research group monitored the explosion using an instrument on a NASA satellite. In their study, published earlier this summer, they estimated the eruption to be even larger, adding around 150 million tons of water vapor to the stratosphere — three times what Voemel’s study found.

In that study, scientists also concluded that the unprecedented cloud could temporarily affect Earth’s average global temperature.

Voemel acknowledged that the satellite imaging may have observed parts of the cloud that the balloon instruments couldn’t pick up, making their estimate higher.

Anyhow, he said the Tonga blast was unlike anything seen in recent history, and examining its aftermath could provide new insights into our atmosphere.