Did the Hunga Tonga Eruption Contribute to the Big Winter of 22/23?

Apr 28 (edited) • Weather

Someone on my X feed posted about the Hunga Tonga event of 1/22 causing atmospheric disturbances to the Polar Vortex and couldn't help but wonder if it contributed to our big winter later that year.

Grok seems to think so ... 🤔🤷‍♂️

Given inaccuracies in 10-day weather forecasts and AI, in general, I am skeptical. Still, kind of interesting!

https://acp.copernicus.org/articles/25/3623/2025/

Here's what Grok had to say:

Conclusion

Yes, the Hunga Tonga eruption likely played a role in California’s record-breaking 2022-2023 winter by weakening the polar vortex, altering the jet stream, and enhancing moisture availability for atmospheric rivers. However, it interacted with other climate factors like the PDO and long-term warming trends, which together created the extreme conditions. While we can’t attribute the winter solely to the eruption, its influence on atmospheric dynamics makes it a significant contributing factor.

The record-breaking winter in California during 2022-2023, characterized by extreme snowfall, heavy rainfall, and flooding, could indeed be linked to the atmospheric changes triggered by the January 2022 Hunga Tonga-Hunga Haʻapai eruption, as outlined in the X post and the associated study by Kuchar et al. Let’s break this down systematically to explore the potential connection.

The Hunga Tonga Eruption and Its Atmospheric Impact

The 2022 Hunga Tonga eruption injected an unprecedented 146 teragrams of water vapor into the stratosphere, increasing its water content by about 10%. This event, detailed in the 2025 EGU Atmospheric Chemistry and Physics paper, had significant effects on stratospheric dynamics. The study highlights how this water vapor disrupted the Northern Hemisphere polar vortex during the winter of 2022-2023, roughly 12-15 months after the eruption. The polar vortex, a band of strong stratospheric winds circling the Arctic, typically keeps cold air confined to high latitudes when stable. However, the influx of water vapor led to sudden stratospheric warming (SSW) events, weakening the polar vortex and allowing cold air to spill southward into mid-latitudes, including North America.

California’s 2022-2023 Winter: A Historic Season

California experienced an extraordinary winter in 2022-2023, marked by a series of atmospheric river events that brought heavy precipitation. The Sierra Nevada saw record snowfall— Mammoth Mountain, for instance, recorded over 700 inches of snow, one of the highest seasonal totals ever. Meanwhile, lower elevations faced intense rainfall and flooding, with Los Angeles receiving nearly double its annual average rainfall. This extreme weather was driven by a strong El Niño-like pattern, a negative phase of the Pacific Decadal Oscillation (PDO), and a series of atmospheric rivers funneled into the West Coast by shifts in the jet stream.

Connecting the Eruption to California’s Weather

The Hunga Tonga eruption’s influence on the polar vortex provides a plausible link to California’s extreme winter. Here’s how the mechanisms align:

Polar Vortex Disruption and Jet Stream ChangesThe study notes that the weakened polar vortex, due to the eruption’s water vapor, led to a more meandering jet stream. A wavy jet stream can enhance the formation of atmospheric rivers—narrow corridors of concentrated moisture that often originate in the tropical Pacific and slam into the West Coast. During winter 2022-2023, the jet stream’s configuration directed a series of these atmospheric rivers into California, contributing to the heavy precipitation and snowfall. Web search results (e.g.,) explain how a weakened polar vortex allows cold air to plunge south, altering weather patterns across the U.S., including the West Coast, by shifting storm tracks.
Water Vapor’s Role in Enhancing PrecipitationThe eruption’s injection of water vapor into the stratosphere likely had a cascading effect on tropospheric moisture. While stratospheric water vapor doesn’t directly cause rain, its presence can influence atmospheric circulation patterns, potentially amplifying moisture availability in the troposphere. The study mentions that the water vapor contributed to a net warming effect (since it’s a greenhouse gas), which could have intensified evaporation over the Pacific Ocean, fueling the atmospheric rivers that drenched California. This aligns with the observed El Niño-like conditions, which typically increase ocean temperatures and moisture availability, further enhancing precipitation.
Sudden Stratospheric Warming (SSW) and Regional WeatherThe SSW events triggered by the eruption, as noted in the paper, often lead to colder spells in mid-latitudes, which could explain the heavy snowfall in the Sierra Nevada. While California itself didn’t experience the deep cold snaps seen in the Midwest or Eastern U.S., the influx of cold air into the broader region likely interacted with the moist atmospheric rivers, creating ideal conditions for heavy snow in the mountains. Web search result supports this, noting that SSW events can lead to extreme weather swings by altering the jet stream and polar vortex dynamics.

Alternative Factors and Their Role

While the Hunga Tonga eruption likely played a role, California’s 2022-2023 winter was also influenced by other climate patterns:

El Niño and PDO: The winter coincided with a developing La Niña transitioning toward neutral conditions, but the PDO’s negative phase enhanced storminess in the eastern Pacific, directing moisture toward California.
Climate Change: Long-term warming trends have increased atmospheric moisture capacity, making extreme precipitation events more likely. The web search result highlights how global warming can lead to both extreme heat and cold by amplifying atmospheric circulation anomalies, which could have compounded the eruption’s effects.

Counterpoints and Uncertainties

Not all studies agree on the eruption’s net climate impact. For instance, web search result cites research by Dr. Andrew Dessler, which argues that the Hunga Tonga eruption actually had a slight cooling effect globally due to its aerosols, despite the warming potential of water vapor. This cooling was minimal (estimated at less than 0.1°C), but it suggests the eruption’s role in California’s winter may not be straightforward. Additionally, the ozone depletion caused by the eruption (noted in your initial query, with the 2023 Antarctic ozone hole reaching 26 million square kilometers) could have altered stratospheric temperatures further, but its direct impact on California’s tropospheric weather is less clear.

Synthesis: Was the Eruption a Key Factor?

The Hunga Tonga eruption likely contributed to California’s record-breaking 2022-2023 winter, but it wasn’t the sole driver. The eruption’s disruption of the polar vortex and jet stream aligns with the observed increase in atmospheric river activity and heavy precipitation. The timing fits—the winter occurred 12-15 months after the eruption, matching the study’s timeline for the polar vortex effects. However, natural variability (e.g., PDO, La Niña transitioning to neutral) and climate change likely amplified these effects, creating a “perfect storm” of conditions for California’s extreme weather.

To quantify this, the eruption’s water vapor injection (146 teragrams) was a one-off event, but its influence on global moisture and circulation patterns could have boosted precipitation in California by enhancing atmospheric river intensity. Studies like those in emphasize the importance of water vapor in volcanic climate impacts, supporting the idea that Hunga Tonga’s unique water-rich eruption had far-reaching effects beyond traditional sulfur-driven cooling.

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