The Science Of Hunga Tonga Global Warming - Part 1

None of this is ‘settled science’. A Hunga Tonga event hasn’t happened before - at least, it hasn’t happened where we can monitor in detail and in real time the ‘unprecedented’ injection and global distribution of water vapour into the stratosphere and analyse the subsequent effects on global temperature, atmospheric circulation patterns and stratospheric ozone concentration. The science is a work in progress and does not bear the stamp of ‘consensus’ - not that any legitimate science should ever bear that stamp anyway.

The conclusion herein that Hunga Tonga is driving the current spike in global mean surface temperature is ‘controversial’. We have of course the usual suspects on the global warming side of the fence who are naturally eager to downplay the effects of Hunga Tonga on current global temperature, but even the more climate sceptical Dr Roy Spencer and Dr John Christy at the university of Alabama, Huntsville, are not giving credit to Hunga Tonga, preferring instead to point the finger of blame at the current modest developing El Nino:

The global atmospheric temperature anomaly increased slightly in October from the record value observed in September to +0.93°C (+1.67°F) above the 30-year average, setting a new anomaly record for the 45-year satellite era. This marks three months in a row that the previous monthly temperature record was superseded as the current El Niño came on in force earlier than is typical, warming up the atmosphere in these mid-year (and already warm) months. Though the tropics this month were warmer than any other October, the early-year months of Jan-Apr still hold the records for the largest departures from average in this equatorial belt. Besides the global record for departure from average, this month produced record departures for all months for several regional areas such as the global oceans, NH land, SH oceans, tropical land, and more.

A continuing and interesting question at this point is, “When will the El Niño and its warming influence peak?” Since it began 4-5 months earlier than usual, will it peak earlier as well, or will it continue to maintain its strength until the typical peak in Feb-Apr? We will have to wait and see.

I pointed out in my previous post that El Nino is currently much weaker than the events of 1998 and 2016. Spencer and Christy’s argument appears to rest on the fact that the El Nino started developing earlier than usual, however it also appears to be peaking at the usual time, probably in November or December. Also, it built up very slowly, barely registering as a proper El Nino for months. It seems odd to me that this El Nino, now, should be driving such a huge departure from average mean global surface temperatures. Spencer and Christy are clutching at straws in my opinion when they say that October 2023, in absolute terms, is still slightly cooler than previous months (recall that the UAH temperature graph plots monthly anomalies - departure from the normal - not absolute temperature):

In terms of absolute temperature, October’s global value of 264.87K was cooler than the last three months (July hit 266.06K) simply because those months are naturally warmer as the global temperature is warmest in July and coolest in January. The tropics have a different pattern with the warmest month being April and coolest in July on average, so that the current October tropical warmth of 274.23K (anomaly of +1.00 K) is slightly cooler than the warmest month of 274.79 (April 1998).

The fact is, July, August, September and October 2023 have all been anomalously very warm and proposing a very modest developing El Nino, even if it started earlier than usual, as the physical source of that warmth, does not to me seem credible.

Spencer and Christy also maintain, in their August 2023 report (without linking to the source of their information) that Hunga Tonga would only affect global mean surface temperatures by a ‘few hundredths of a degree’:

As mentioned last month, along with the natural warming of the current El Niño event, we are analyzing the potential (and natural) warming impacts of the 2022 eruption of the Hunga Tonga submarine volcano and its injection of water vapor into the stratosphere. Normally, a major tropical eruption would send large amounts of gasses such as sulfur dioxide up that high which form sun-reflecting aerosols leading to a cooling of the Earth’s lower atmosphere. However, the Hunga Tonga submarine volcano eruption injected large amounts of water vapor into the stratosphere which may be overriding any aerosol cooling effects and lead to a net warming of the atmosphere. At this point, it appears this influence will be minor, perhaps a few hundredths of degree.

So it’s not just global warming fanatics who are downplaying the possible effects of Hunga Tonga on global temperature; scientists on ‘our side’ are too. Which means, of course, that it is even more critical to look closely at what the actual science and data say in order to get a clearer picture of what might actually be happening. I’m going to attempt to do that here. It’s going to take a few bite-sized posts though, because it’s complex and I have other things to do which rudely interrupt with brainstorming sessions on Substack! Part 2 to follow.