Hunga Tonga eruption lofted unprecedented water vapor into stratosphere, altering climate before fading
The Jan 2022 Hunga Tonga-Hunga Ha'apai eruption injected roughly 146 teragrams of water vapor into the stratosphere, temporarily affecting temperature, circulation, ozone and radiation, with its influence largely gone by the end of 2023.
On 15 January 2022, the Hunga Tonga-Hunga Ha'apai submarine volcano erupted, thrusting an estimated 146 teragrams of water vapor—about one-tenth of the stratosphere's existing moisture—up to 53 km altitude. The plume quickly encircled the globe, with the highest concentrations residing between 22 and 26 km. Initial climate modelling suggested a radiative forcing of roughly +0.15 W/m², but the extra vapor increased infrared emission, cooling the tropical stratosphere by about 4 K during March-April 2022.
Concurrently, sulfur dioxide formed sulfate aerosols that reflected sunlight, producing a larger net cooling effect. The water vapor also altered atmospheric circulation, leading to a measurable ozone decline in the Southern Hemisphere extra-tropical stratosphere. Over the following two years, the moisture spread with the Brewer-Dobson circulation and its climatic impact waned, with radiative forcing dropping close to zero by the end of 2023.
Why it matters
The eruption showed how massive volcanic water vapor can temporarily reshape atmospheric chemistry and climate dynamics.
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