Will The Eruption Of Hunga Tonga-Hunga Ha’apai Volcano Affect Earth’s Climate?

In April 1991, steam explosions were first observed on a little-known volcano called Mount Pinatubo on the island of Luzon in the Philippines. Within 11 weeks, on the afternoon of June 15, the volcano erupted ten billion tons of pumice and an estimated 17 billion metric tons of sulfur-dioxide. The eruption of Mount Pinatubo was the second-largest eruption of the 20th century. Satellite images tracked the eruption column forming an umbrella cloud reaching a maximum diameter of over 1100 kilometers and a maximum elevation of 35 kilometers above sea level. The ash and sulfur-dioxide reacted with water vapor to form over 30 billion metric tons of sulfuric-acid droplets and other aerosols. The aerosols quickly spread around the tropics and high latitudes, carried there by atmospheric currents along Earth's equator. Over the following months, the aerosol cloud climbed higher into Earth's atmosphere, forming a barrier and scattering or reflecting parts of the sunlight. By August 1991, five percent less solar radiation was reaching Earth's surface, and in response, Earth cooled down by 0.5 degrees for the coming two to three years.

On Saturday, the Hunga Tonga-Hunga Ha'apai volcano erupted in spectacular fashion near the Pacific nation of Tonga, with a volcanic plume and a blast wave seen from space by various weather satellites. An especially powerful explosion produced an ash plume about 150 kilometers (about 100 miles) across and 20 kilometers high, reaching Earth's upper atmosphere. The blast wave travelled twice around the world, as 16 hours after the eruption two peaks in atmospheric pressure were measured at various weather stations in Europe.

The 1991 Pinatubo eruption was a magnitude 6 eruption after the Volcanic Explosivity Index (VEI) scale. The Hunga Tonga-Hunga Ha'apai is (at the moment) classified as a VEI 4 to 5, the largest in the past 30 years.

Mount Pinatubo and Hunga Tonga-Hunga Ha'apai share some geological similarities. Both are volcanos sitting atop subduction zones, where oceanic crust, together with marine sediments and water is pushed down, partially melting in the process. This causes very gas- and sulfur-rich magma to form.

Could the Hunga Tonga-Hunga Ha'apai eruption have also similar effects on the climate as Pinatubo?

It seems unlikely at the moment.

Preliminary observations suggest that the volcano erupted "only" 400,000 metric tons of sulfur-dioxide so far. Recent eruptions with comparable emission levels, like the Chilean Calbuco volcano in 2015 and La Soufriere on the island of Saint Vincent in 2021, had no significant effects on the climate. Based on research done after the Pinatubo eruption, it is believed that a volcano must at least erupt 5 billion tons to affect global temperatures.

First observations of the sulfur dioxide injected into the atmosphere by the volcanic eruption in Tonga. Injections large & high enough to cause 2-3 yrs cooling of Earth are very rare. 20 years ago we published a paper on the reaction of the C sink to the large Pinatubo eruption. pic.twitter.com/G8bQ9cglmC

— Wolfgang Lucht (@W_Lucht) January 16, 2022

The effect of a volcano on the climate depends on various factors, including the magnitude of the explosions, the elevation of the eruption column, the sulfur content of the lava, the site and timing of the eruption.

Volcanic eruptions with marked cooling effects in the past, like Pinatubo in 1991 or Tambora in 1815, happened near the equator, where atmospheric circulation will carry the volcanic cloud around the globe. Hunga Tonga-Hunga Ha'apai is located further south in the Pacific Ocean, likely limiting aerosol dispersal.

As for how long Tonga-Hunga Ha'apai will remain active is unclear. Experts proposed two possible scenarios. The first is that the magma reservoir of the volcano has exhausted itself for now and it will go quiet for the next 10 to 20 years as magma slowly returns. A second scenario is that new magma rises up quickly to replace that which exploded, in which case there might be ongoing eruptions, but likely of minor magnitude.

Source: Forbes