Time for fact-checking as CO2 misinformation surrounds Iceland’s volcanic eruption

A few hours after the eruption of a volcano, around 45km south-west of Reykjavik, spectacular lava-heavy images on social media were becoming interspersed with text-only contributions from people far away. People with opinions.

An X/Twitter user who goes by the name Sir Peter Morris: Just fed up of all the nonsense  confessed to having ‘no idea of the numbers’ but still wanted to type something: ‘I have no idea of the numbers, but I wonder how much the volcano eruption in Iceland and the consequential Co2 it emits, negates the piddling amount of CO2 the UK is bankrupting itself to save?’

British Cheese Party came forward to offer a ‘guess’: ‘Good question. My guess is it equates to an annual Co2 output or most major nations. Maybe the green agenda should staff with volcanic activity rather than granny with her wood burner…’

Searching the platform for mention of CO2 brought forth many more such comments. Steve Ruda: ‘There’s enough co2 belched out there to last 100,000 years ..its all a scam..wish people would wake up . Do some basic geography.’

So what do we tell people like Steve? Well, while it is true that volcanoes contribute to the levels of CO2 in the atmosphere, a significantly large eruption, such as Mount St. Helens, will produce the same amount of CO2 that humans do every two and a half hours.

To put it another way, we’d need around ten Mount St. Helens sized eruptions every day for volcanoes to be equal to humans in terms of CO2 emissions.

In a 2011 paper,  Geologic Survey scientist Terry Gerlach explained: ‘The nearly 9-hour duration of both the Mount St. Helens and Pinatubo paroxysms gives average CO2 emission rates of about 0.001 and 0.006 gigaton per hour, respectively.

‘Intriguingly, the anthropogenic CO2 emission rate of 35 gigatons per year— equivalent to 0.004 gigaton per hour—is similar. So, for a few hours during paroxysms, individual volcanoes may emit about as much or more CO2 than human activities. But volcanic paroxysms are ephemeral, while anthropogenic CO2 is emitted relentlessly from ubiquitous sources.’

Gerlach concluded that human CO2 emissions were more than 90 times greater than global volcanic carbon dioxide emissions.

What the X-sceptics might want to worry about are supervolcanoes. Volcanoes are rated by the Volcanic Explosivity Index, which is used to measure the magnitude of earthquakes. The Index runs from zero to eight and, for perspective, Mount Vesuvius, which wiped out Pompeii only makes it to five.

A category 8 supervolcano eruption is not, fortunately, a frequent occurrence – the last one happened around 26,500 years ago. The most famous such volcano on Earth is Yellowstone and it is believed that should that erupt it would generate the same amount of CO2 that  humans produce in a year.

But while contributing to CO2 levels, supervolcanoes would not contribute to global warming. In 1815, the eruption of  Tambora in Indonesia (7 on the scale) led to the following year being called ‘the year without summer’.

The more recent eruption of Mount Pinatubo (1991) caused the global air temperature to drop by 0.5°C between 1991 and 1993.

As for Steve? Well, it’s probably best to ignore him.