Tongan blast could warm the Earth
When an undersea volcano erupted in Tonga in January, its watery blast was huge and unusual — and scientists are still trying to understand its impacts.
The volcano, known as Hunga Tonga-Hunga Ha’apai, shot millions of tonnes of water vapour high up into the atmosphere, according to a study published yesterday in the journal Science.
The researchers estimate the eruption raised the amount of water in the stratosphere — the second layer of the atmosphere, above the range where humans live and breathe — by about 5 per cent.
Now, scientists are trying to figure out how all that water could affect the atmosphere, and whether it might warm Earth’s surface over the next few years. “This was a once-ina-lifetime event,” said lead author Holger Voemel, a scientist at the National Center for Atmospheric Research in Colorado.
Big eruptions usually cool the planet. Most volcanoes send up large amounts of sulfur, which blocks the sun’s rays, explained Matthew Toohey, a climate researcher at the University of Saskatchewan who was not involved in the study.
The Tongan blast was much soggier: The eruption started under the ocean, so it shot up a plume with much more water than usual.
And since water vapour acts as a heat-trapping greenhouse gas, the eruption will probably raise temperatures instead of lowering them, Toohey said.
It’s unclear just how much warming could be in store.
The water vapour will stick around the upper atmosphere for a few years before making its way into the lower atmosphere, Toohey said.
But it’s hard for scientists to say for sure, because they’ve never seen an eruption like this one.
The stratosphere stretches from about 12km to 50km above Earth and is usually very dry, Voemel explained.
Voemel’s team estimated the volcano’s plume using a network of instruments suspended from weather balloons. Usually, these tools can’t even measure water levels in the stratosphere because the amounts are so low, Voemel said.
Another research group monitored the blast using an instrument on a Nasa satellite.
In their study they estimated the eruption to be even bigger, adding about 150 million metric tonnes of water vapour to the stratosphere — three times as much as Voemel’s study found.
Voemel acknowledged that the satellite imaging might have observed parts of the plume that the balloon instruments couldn’t catch, making its estimate higher.
Either way, he said, the Tongan blast was unlike anything seen in recent history, and studying its aftermath may hold new insights into our atmosphere.