Climate Etc. Confirms That 2023 Record Warm Year Plus Three SSWs Were Likely Due to Hunga Tonga

Well, I must say, it’s about time that a major climate sceptic blog caught up with what I’ve been banging on about for eight months now!

Javier Vinos at Judith Curry’s Climate Etc. says:

The unlikely volcano, the warmest year, and the collapse of the polar vortex.

The climate events of 2022-24 have been were truly extraordinary. From an unlikely undersea volcanic eruption to the warmest year on record to the collapse of the polar vortex after three sudden stratospheric warming events. This rare convergence presents a unique learning opportunity for climatologists and climate aficionados alike, offering insights into a climate event that may not be repeated for hundreds or even thousands of years.

Never before have we witnessed an undersea volcanic eruption with a plume capable of reaching the stratosphere and depositing a large amount of vaporized water. This extraordinary event occurred in January 2022 when the Hunga Tonga volcano erupted. The conditions for such an event are rare: the volcano must be deep enough to propel enough water with the plume, but not too deep to prevent it from reaching the stratosphere. Most undersea volcanoes do not produce plumes at all, which makes Hunga Tonga’s eruption all the more remarkable.

The effect of the Hunga Tonga eruption, however, is quite the opposite. While there was some sulfur dioxide associated with Hunga Tonga, the main impact was from water vapor. Water vapor is a potent greenhouse gas, so the sudden 10% increase in stratospheric water vapor in a single day increased stratospheric opacity to outgoing infrared radiation. Unlike the lower troposphere, where the greenhouse effect is relatively saturated, the stratosphere, well above the Earth’s average emission altitude (about 6 km), experiences a much more pronounced effect from the addition of water vapor. Also, the increased stratospheric water vapor content enhances infrared emissions from the stratosphere, thereby cooling it significantly.

We can conclude that 2023 stood out as an exceptionally unusual record-warm year. While it rivaled very strong El Niño years in terms of exceeding previous temperature records, it did not actually fall into that category. Remarkably, despite the lack of a strong El Niño, it managed to set the highest temperature record by the largest margin in the data set spanning a century and a half.

The unlikely volcanic eruption is the likely cause of the extraordinary warming, which in turn led to the occurrence of the unprecedented three SSW events. Our understanding of the effects of these events supports this interpretation.

I’ve been pointing the finger at Hunga Tonga for the exceptional warmth in 2023 since the beginning of August last year, plus firmly refuting the many misguided attempts to blame El Nino. Two weeks ago, I also suggested that Hunga Tonga might also be the cause of the very rare three sudden stratospheric warmings:

I haven’t looked at this closely yet but one thing leaps out at me. We’ve got an ‘unprecedented’ third sudden stratospheric warming. Stratospheric warmings, according to one of the studies cited by the author of the Conversation article above, are intimately connected with stratospheric ozone:

The stratospheric ozone layer accounts for 90 % of the total existing atmospheric ozone and plays fundamental roles for atmospheric processes and for life on Earth. Ozone in this atmospheric region provides a vital shield against harmful ultraviolet (UV) radiation, preventing the most energetic UV-C and UV-B wavelengths (wavelength bands below 300 nm) from reaching the Earth's surface. UV radiation is absorbed by ozone in the stratosphere via very exothermic reactions. Therefore ozone is the main player in shaping the vertical temperature profile in the stratosphere and has a fundamental role in the interactions between radiation and dynamics in this region, as well as in the exchange of air masses with the troposphere.

Well, what do you know? The Hunga Tonga volcanic eruption is expected to have very significant effects upon stratospheric ozone, the most significant of which are projected to occur . . . . . . right now!

I have no idea at this point whether the disruption in stratospheric ozone caused by the injection of water vapour high into the stratosphere by Hunga Tonga may affect the likelihood of SSWs, but it seems to me that it is worth investigating as an alternative to saying ‘it was global warming wot dunnit’ yet again.