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When volcanoes go bad

08 Sep 2021 | News Roundup

One claim that global warming skeptics sometimes make is that volcanoes give off more GHGs than humans. Which would be a fairly decent “gotcha” were it not for one small problem: they don’t. Big volcanic eruptions have dramatic effects, primarily cooling, due to a host of particulates, sulphur dioxide and so on, whereas most of the time they just seep out GHGs in what, though as usual we know a lot less than people think, seem to be fairly small relative not just to the vast carbon cycle but even to our own minor contribution to it. Unfortunately, as you know, all effects of climate change are bad and there’s nothing it can’t do including increasing stress. And now it’s even going to make volcanic eruptions worse. Researchers say.

As the Duke of Wellington once retorted, if you’ll believe that you’ll believe anything. Namely that “large-magnitude eruptions will have greater effects as the climate continues to warm. However, the cooling effects of small- and medium-sized eruptions could shrink by as much as 75%.” And just for laughs, we read on, to see how warming would make volcanoes worse, since surely they at least are already hot enough that a fraction of a degree won’t matter, and volcanic eruptions seem to be as close to hell as they could possibly be.

It works like this: “as the atmosphere warms due to climate change, the plumes of ash and gas emitted by large, but infrequent, volcanic eruptions will rise ever higher. Climate change will also accelerate the transport of volcanic material – in the form of small, shiny droplets called volcanic sulfate aerosols – from the tropics to higher latitudes. For large eruptions, the combined effect of these phenomena will cause the haze created by volcanic aerosols to block more sunlight from reaching Earth’s surface, ultimately amplifying the temporary cooling caused by volcanic eruptions.”

The article, or at least the Eurekalert! press release, suffers no pangs of self-doubt. After noting that when Mount Pinatubo blew its top in 1992 it cooled the planet by about 0.5°C, it says flatly “In comparison, human activities have warmed global temperatures by over 1 degree Celsius since 1850. However, the effect of volcanic aerosols only persists for one or two years, while anthropogenic greenhouse gases will affect the climate for centuries.”

As we’ve noted before, the weird thing about this latter statement is that if it is true, then non-anthropogenic GHGs should do the same, and we should be experiencing the long-term effects of fluctuations back when Queen Elizabeth’s courtiers were wearing ruff collars or some such. But back then they didn’t have computers, which might make all the difference.

“The researchers used global climate models combined with volcanic plume models to simulate how the aerosols emitted by volcanic eruptions might be affected by climate change. They found that for large eruptions like Mount Pinatubo, which typically occur once or twice per century, climate change will cause the plumes to rise higher and the aerosols to spread faster over the globe, resulting in a cooling effect amplified by 15%. Changes in ocean temperatures are expected to further amplify the cooling, and the melting of ice sheets is also projected to increase volcanic eruptions frequency and size in places such as Iceland. However, for moderate-sized eruptions such as the 2011 Nabro eruption in Eritrea, which typically occur on a yearly basis, the effect will be reduced by about 75% under a high-end warming scenario. This is because the height of the tropopause – the boundary between the troposphere and the stratosphere above it – is predicted to increase, making it harder for volcanic plumes to reach the stratosphere.”

Those who actually understand computer models, which you’d hope would include these authors, know that atmospheric physics is something they do remarkably poorly, especially cloud formation. Meaning that the switch from “might be affected” to “will cause” above is inexcusable sloppiness. Not to mention the claim by one of the coauthors that the sky is more or less literally on fire: “Due to more frequent and more intense wildfires, as well as other extreme events, the composition of the upper atmosphere is changing in front of our eyes, and so is our understanding of the consequences of these changes.” And it’s going to get worse.

The research, we mean. “The authors hope to bring together more volcanologists and climate scientists to understand not only the mechanics behind volcanic plume rise and aerosol lifecycle, but also how changes in eruption frequency and magnitude, driven by deglaciation and extreme precipitation, will shape the future climatic effects of volcanic eruptions.” Our prediction is that a giant cloud of alarming press releases will rise up and overheat the debate.

One comment on “When volcanoes go bad”

  1. An unknown number of subsea vents are continually injecting CO2 into the oceans, which dissolves, moves around for several thousand years, then outgasses when it circulates to a warmer part of the surface waters. The CO2, at least in part, comes from subterranean gas, oil and coal deposits, and so shares the carbon isotope fingerprint from the burning of fossil fuels, so this CO2 looks just like human-burnt fossil fuels.

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