Possible Association Between Recent Climate Extremes And The 2022 Hunga Tonga-Hunga Ha'apai Eruption

An unusually large increase in global mean temperature developed in 2023 for reasons not yet fully understood. The most immediate culprit is a major El Niño that formed against the backdrop of global warming. Other factors may include sharp declines in ship aerosol emissions over the North Pacific this past decade, and perhaps also an unexpected climate-system response to the January 2022 eruption of Hunga Tonga-Hunga Ha’apai (Tonga), a submarine volcano that injected an unprecedented amount of water vapor into the stratosphere. Current literature suggests only small direct radiative effects, but dynamic consequences of the eruption are poorly known. Here, we utilize reanalysis to examine weather and climate extremes since the eruption, and find that unusually large standardized anomalies (+/- 4 to 6 sigma from 20-year climatology) may provide a Tonga “fingerprint”. Among the extreme events of interest are the record March 2022 Antarctic heat wave and the 2022–2023 La Niña. We hypothesize that the increased water vapor from the eruption and subsequent cooling of the lower stratosphere intensified the westerlies over the pacific and strengthened the Walker circulation. The intensification of the Walker circulation resulted in the third consecutive La Niña, which in turn amplified the El Niño that emerged in 2023. Further research includes sensitivity tests to determine whether the third La Niña would have occurred without the injection of water vapor from the Eruption.