On climate, as on many contemporary policy issues, there is a tendency for people on both sides to dig in, jump on events or arguments that seem to confirm their approach, while stomping on those that don’t in hobnail boots. Which brings us to the eruption of the Hunga Tonga-Hunga Ha’apai volcano on January 15 of last year, the most violent in the modern instrument era. It seems very clear that this event may have had a dramatic climate impact unless it did not.

Yes, that’s our considered opinion. As Roger Pielke Jr. commented on August 8, “Almost all the research that will be done on its effects on climate hasn’t been done yet”. It is tempting to note that volcanic eruptions, which are noted for being massive, more powerful even than hydrogen bombs, are also noted for their climate impact, including the detonation of Mount Pinatubo in 1991 that seems to have cooled the climate for several years. And also that most eruptions have a cooling effect because of the sulphur and aerosols they inject into the atmosphere.

Pinatubo, the second-most-powerful eruption of the 20^th century after Novarupta in Alaska in 1912, sent an ash cloud 40 km (25 miles) up into the sky, deposited lava in layers 200 metres thick (OK, “pyroclastic flows” if you want to be all volcanologist about it), killed over 800 people directly, sent an estimated 17 million tonnes of sulphur dioxide into the atmosphere, and is thought to have cooled the globe by almost half a degree Celsius and caused the “Summer that Wasn’t” of 1992. (Just as the even more savage eruption of Tambora in Indonesia in 1815 caused a very hard “Year Without Summer” in 1816; in both cases the lag indicates the severity and duration of such effects.)

So what of Hunga Tonga etc.? It was bigger than Pinatubo, and indeed bigger than anything since Krakatoa in 1883, which again cooled the planet by an estimated half-degree or more for months. But it was also rather different, in that its primary effect seems to have been to add vast amounts of water vapour to the atmosphere, partly because it happened 150 metres below the surface of the sea. And water vapour is, as any climate alarmist politician, activist or journalist probably does not know, the most potent greenhouse gas by far.

Yes, that’s right. The most potent. Indeed, the generalized panic over CO2 relies overwhelmingly on a so-called amplification mechanism where a small warming from the dreaded carbon pollution in turn causes more evaporation to raise the amount of water in the air and trigger climate breakdown boiling. And Hunga skipped that step and just pumped in the water directly, adding perhaps as much as 10% to the normal load. Or maybe 30%, climate being a far from exact science IRL.

To its credit, in a piece larded with the usual stuff about “savage peaks” in local temperature The Economist did allow that “the climate has natural variations” and that Hunga might have had an effect since “Water vapour is a powerful greenhouse gas” though it insisted that “if Hunga is playing a role, it is one that is already waning”.

Given our skepticism about the impact of CO2, and the existence of any sort of climate crisis let alone a man-made one, we might be expected to pounce and say the opposite, that whatever unusual heat we might have seen this year is because of that eruption. Instead we’re going to say, as we have before, that climate is very complicated, its feedback mechanisms are transcomputable, and that we should urgently rush to wait and see.

We would add here that estimates of how long Pinatubo affected the climate measurably vary from NASA’s “almost two years” to Eos’s “around three years”. Part of the problem being that to measure its impact you have to know what would have happened otherwise and, computer models and their follies notwithstanding, we don’t. But some things are predictable.

Including the politicization of science around climate. We quoted Roger Pielke Jr. above, but selectively. What he actually Tweeted, or Xed, in full is a lot more damning:

“The Hunga-Tonga eruption is rapidly becoming the lab leak of climate science
Almost all the research that will be done on its effects on climate hasn’t been done yet
But already some climate scientists are warning that to ask about its climate effects is disinformation”

So you know who the real anti-science “deniers” are, and who the people who really don’t have open minds are. The usual skeptical scoundrels are suggesting this eruption might cause some warming in the next couple of years, but we’re far from sure and we should wait and see. (As David Whitehouse put it on Net Zero Watch, “The effect could be quite small, or it might not.” Hardly the voice of dogmatism.)

For the swaggering tone of certainty, look to the alarmists. For instance the U.S. National Park Service uses the devastating cooling following Tambora to “prove” that warming is bad. As they would, saying:

“Those who survived this little ice age witnessed the devastating impacts that a few degrees of change can cause. By 2050, the average global temperature is expected to increase by four degrees. However, unlike the global change in climate in 1816, this temperature change will be permanent and caused by human activity, not nature. People all around the world are leaving their homes to escape the effects of human-driven climate change. In the U.S. alone, we are experiencing more frequent and intense storms, hurricanes, tornados, wildfire, and drought. Is the Year without Summer a glimpse of what is to come? That depends on us.”

Or on whether cold rather than heat causes bad weather, since in fact in 2023 the U.S. experienced far less wildfire than normal, and hurricanes are trending down. But these are mere facts.