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Abstract The Hunga Tonga‐Hunga Ha'apai (Hunga) volcanic eruption in January 2022 injected a substantial amount of water vapor and a moderate amount of SO2into the stratosphere. Both satellite observations in 2022 and subsequent chemistry‐climate model simulations forced by realistic Hunga perturbations reveal large‐scale cooling in the Southern Hemisphere (SH) tropical to subtropical stratosphere following the Hunga eruption. This study analyzes the drivers of this cooling, including the distinctive role of anomalies in water vapor, ozone, and sulfate aerosol concentration on the simulated climate response to the Hunga volcanic forcing, based on climate simulations with prescribed chemistry/aerosol. Simulated circulation and temperature anomalies based on specified‐chemistry simulations show good agreement with previous coupled‐chemistry simulations and indicate that each forcing of ozone, water vapor, and sulfate aerosol from the Hunga volcanic eruption contributed to the circulation and temperature anomalies in the SH stratosphere. Our results also suggest that (a) the large‐scale stratospheric cooling during the austral winter was mainly induced by changes in dynamical processes, not by radiative processes, and that (b) the radiative feedback from negative ozone anomalies contributed to the prolonged cold temperature anomalies in the lower stratosphere (∼70 hPa level) and hence to long lasting cold conditions of the polar vortex.
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The January 2022 Hunga eruption cooled the southern hemisphere in 2022 and 2023
Abstract The 2022 Hunga volcanic eruption injected a significant quantity of water vapor into the stratosphere while releasing only limited sulfur dioxide. It has been proposed that this excess water vapor could have contributed to global warming, potentially pushing temperatures beyond the 1.5 °C threshold of the Paris Climate Accord. However, given the cooling effects of sulfate aerosols and the contrasting impacts of ozone loss (cooling) versus gain (warming), assessing the eruption’s net radiative effect is essential. Here, we quantify the Hunga-induced perturbations in stratospheric water vapor, sulfate aerosols, and ozone using satellite observations and radiative transfer simulations. Our analysis shows that these components induce clear-sky instantaneous net radiative energy losses at both the top of the atmosphere and near the tropopause. In 2022, the Southern Hemisphere experienced a radiative forcing of −0.55 ± 0.05 W m⁻² at the top of the atmosphere and −0.52 ± 0.05 W m⁻² near the tropopause. By 2023, these values decreased to −0.26 ± 0.04 W m⁻² and −0.25 ± 0.04 W m⁻², respectively. Employing a two-layer energy balance model, we estimate that these losses resulted in cooling of about −0.10 ± 0.02 K in the Southern Hemisphere by the end of 2022 and 2023. Thus, we conclude that the Hunga eruption cooled rather than warmed the Southern Hemisphere during this period.
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- Award ID(s):
- 2151093
- PAR ID:
- 10579221
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Communications Earth & Environment
- Volume:
- 6
- Issue:
- 1
- ISSN:
- 2662-4435
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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