According to a recent study published in the journal Nature Climate Change, the January 2022 eruption of Hunga Tonga-Hunga Ha’apai caused temporary warming over the Pacific and could push us over the 1.5 degree Celsius threshold set by the United Nations.
While volcanoes bring fire and chaos during their eruption, they usually have a cooling effect on the overall climate. That’s because eruptions release a whole bunch of sulfur into the air, which makes its way high into the atmosphere where it settles down in the form of tiny reflective particles. A sufficiently violent eruption could block enough sunlight to drop the average global temperature by a few degrees Celsius for a few years or more. Which is why it’s so weird that Hunga Tonga-Hunga Ha’apai appears to have caused a warming effect over the Pacific.
When the volcano popped off, it sent an estimated 146 metric megatons of water into the stratosphere, several miles above the planet’s surface. That water vapor acts as a greenhouse gas, trapping heat and raising the average temperature over the Pacific. That warming is temporary, but it’s an added pressure on an already strained system.
The United Nations’ Paris Agreement set a threshold of 1.5 degrees Celsius over the pre-industrial average. That’s the horizon we’re trying not to cross, but it’s looking increasingly likely that we might. Importantly, crossing 1.5 C isn’t a “point of no return” but every fraction of a degree of warming we avoid is a good thing.
In May 2022, the World Meteorological Organization predicted a 50-50 chance that we would crest 1.5 C of warming in the following five years. Taking the Hunga Tonga-Hunga Ha’apai eruption into account, the new study predicts an additional 7% probability, tipping the scales in favor of excessive warming. Of course, we can’t control volcanic eruptions, but we can do something about our own contributions to global climate change before what buffer we have remaining runs out.