I was watching footage of the new mini-volcano in Iceland – Mount Fagradalsfjall – the other day on YouTube, with the inevitable result that the algorithm pushed other volcano footage at me. Next up was the Shishaldin volcano in the Alaskan Aleutian islands. And that set me thinking that there seems to have been a lot of seismic and volcanic activity recently. Of course, there is always the possibility that – as with reports of “extreme” weather and climate records world-wide – we are simply more aware, thanks to 24/7 news coverage, the ubiquity of the internet and smart phones and so on, of such incidents, rather than them actually becoming more frequent.

The vlogger whose excellent drone footage of Mount Fagradalsfjall I was watching, made mention of the various dangerous gases associated with it, and he also talked about the amount of CO2 being released by the volcano. For many people this is probably nothing new, but I hadn’t really looked into the subject before. It’s time to share my findings.

These are that the scale of volcanic CO2 emissions can’t be stated with any great certainty. For example, if you believe Australian climate sceptic and geologist Ian Plimer (author of “Heaven and Earth – Global Warming: the Missing Science”, published in 2009) you might conclude that volcanic CO2 emissions are rather substantial, and little understood. He points out (at page 217) that although the proportion of gases emitted varies from volcano to volcano, typically the proportion of CO2 is in the region of 8-12% (H2O being the main gas, at 70-80%, the other main gases being nitrogen and sulphur dioxide – both less than the amount of CO2 emitted – with minor proportions being hydrogen, carbon monoxide, sulphur, chlorine and argon). He also points out (lest we get too excited about the warming implications of volcanoes) that volcanic aerosols scatter incoming short-wave solar radiation, resulting in cooler surface and troposphere temperatures (but stratosphere warming). He also argues that we under-estimate the amount of CO2 released by volcanic activity, because we don’t take sufficient cognisance of submarine volcanoes.

This is obviously dangerous talk, as is the statement in his book (on page 413) to the effect that volcanoes emit more CO2 than the world’s cars and industries combined. It is so dangerous that the Guardian has gone to great lengths to discredit it, especially in the wake of his book being published. In November 2009, George Monbiot argued in the Guardian that the BBC’s flagship radio programme Today was wrong to give Ian Plimer airtime. Following a debate between Ian Plimer and George Monbiot and an interview of him by James Randerson that year, two articles damning him and his views followed in quick succession, here and here. In the wake of the Eyjafjallajokull eruption the following year, which caused such problems for the global airline business, the Guardian returned to the fray. Earlier this month the Guardian was on the warpath again. Clearly Ian Plimer is a dangerous heretic who must be silenced.

Having said all that, I have no idea whether Professor Plimer is on the money, or whether he’s talking rubbish. I am not a scientist, let alone a climate scientist or a vulcanologist. Let’s assume Professor Plimer is wrong, the Guardian is correct, and volcanoes are nothing to worry about – at least so far as their CO2 emissions are concerned. What do the “official” organisations have to say about the subject?

The US National Oceanic and Atmospheric Administration (NOAA) is pretty clear:

Human activities emit 60 or more times the amount of carbon dioxide released by volcanoes each year. Large, violent eruptions may match the rate of human emissions for the few hours that they last, but they are too rare and fleeting to rival humanity’s annual emissions. In fact, several individual U.S. states emit more carbon dioxide in a year than all the volcanoes on the planet combined do.

They also make Professor Plimer’s other, related, point:

Today, rather than warming global climate, volcanic eruptions often have the opposite effect. That’s because carbon dioxide isn’t the only thing that volcanoes inject into the atmosphere. Even small eruptions often produce volcanic ash and aerosol particles.

Whether from small or large eruptions, volcanic aerosols reflect sunlight back into space, cooling global climate. The 1815 eruption of Mount Tambora produced enough ash and aerosols to cancel summer in Europe and North America in 1816.

Which is a rather scary thought. As is the historic activity of volcanoes, if it were repeated today:

Volcanic activity today may pale in comparison to the carbon dioxide emissions we are generating by burning fossil fuels for energy, but over the course of geologic time, volcanoes have occasionally contributed to global warming by producing significant amounts of carbon dioxide and other greenhouse gases.

For example, some geologists hypothesize that 250 million years ago, an extensive flood of lava poured continually from the ground in Siberia perhaps hundreds of thousands of years. This large-scale, long-lasting eruption likely raised global temperatures enough to cause one of the worst extinction events in our planet’s history. Current volcanic activity doesn’t occur on the same massive scale.

Let’s hope not, anyway.

The cited figure – that humankind produces at least 60 times as much carbon dioxide annually as volcanoes – comes from a 2013 study by Michael Burton, Georgina Sawyer, and Domenico Granieri. Two years earlier:

U.S. Geologic Survey scientist Terry Gerlach summarized five previous estimates of global volcanic carbon dioxide emission rates that had been published between 1991 and 1998. Those estimates incorporated studies reaching back to the 1970s, and they were based on a wide variety of measurements, such as direct sampling and satellite remote sensing. The global estimates fell within a range of about 0.3 ± 0.15 billion metric tons of carbon dioxide per year, implying that human carbon dioxide emissions were more than 90 times greater than global volcanic carbon dioxide emissions.

NASA (https://climate.nasa.gov/faq/42/what-do-volcanoes-have-to-do-with-climate-change/) doesn’t go with either the 60 times or the 90 times figure, preferring to say that “human contributions to the carbon cycle are more than 100 times those from all the volcanoes in the world – combined.”

Let’s leave Professor Plimer out of it and go with the measurements that most people are likely to rely on. We are left with a range of figures, such that humankind annually (in the absence of unusual levels of volcanic activity in any one year) produces around 60, 90 or 100 times as much CO2 as volcanoes. The “official” websites to which I have referred (as well as the Guardian, for that matter) do seem anxious to tell us that in the scheme of things, volcanoes are pretty insignificant, so far as CO2 emissions are concerned. Which I find interesting, not least since depending on who you believe, the UK’s CO2 emissions are less than 1% of humankind’s global CO2 emissions on an annual basis. Our World in Data puts the figure at 0.93%. Wikipedia puts it at “under 1%”). The Worldometer website (which supplies an out of date 2016 figure) puts it at 1.03%. Given that the UK’s annual emissions have fallen since then while most of the rest of the world’s have risen, it seems safe to assume that the UK’s emissions are indeed less than 1% of the global total.

Depending, then, on which of the “official” figures we accept for volcanic CO2 emissions, the UK’s emissions are either on a par annually with those from volcanoes, are a bit less, or are about two thirds of the level of volcanic CO2 emissions (per NASA and Burton, Sawyer, and Granieri). And if volcanic emissions are such small beer, such that we can safely discount them and not worry about them, then why the hysteria from the likes of XR and Just Stop Oil about UK emissions? Perhaps it’s time for a new protest group – Just Stop Volcanoes.