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Volcanoes innocent - OK?

Dr Ted Nield, Editor

Geoscentist 21.08 September 2011

Volcanoes are dangerous. In the last two centuries, volcanoes caused about 200,000 deaths worldwide (adding the tsunamis and famines resulting from their eruptions to the direct fatalities caused by pyroclastic flows and lahars). The deadliest historical eruption was Tambora (Indonesia, 1815 – 92,000 dead) and its major instrument of death was starvation. Krakatoa (Indonesia, 1883) killed most of its 36,417 victims by tsunami. Mont Pelée, Martinique, wreaked its 1902 destruction of 29,025 lives by nuée ardente; while in 1985, Nevada del Ruis (Colombia) killed 25,000 by lahar despite a correct forecast.

But – give a dog a bad name. It has become all too easy, in the overheated atmosphere of climate change denial, for those with a little knowledge to say “Hold on – don’t volcanoes give off CO2?” and leap to the conclusion that they emit more than human beings do with all the alacrity that certain early commentators blamed the Oslo bomb blast and Utøya massacre on Al-Qaeda.

Yet, as Colin Summerhayes points out in this month’s second feature, all the world’s volcanoes give off about the same amount of carbon dioxide as human activity in - the State of Florida.

Of course, when they do erupt, volcanoes’ short-term atmospheric effects can be enormous – hence 1815, the ‘year without a summer’ and the famine that came in its wake. But, as Summerhayes writes: “Although the actual rate of CO2 emission per hour during a big eruption may be about the same as human emissions over the same period, eruptions don’t last very long. As a result, big eruptions have small effects when averaged over the long term.”

Charles Lyell famously used Vesuvius and the Bay of Naples as an example of how the effects of the greatest geological paroxysms are eventually effaced by slow, steady, day-to-day processes. Since the rehabilitation of the sudden event into stratigraphic thinking during the 1970s and 1980s, we now know this is not so. We understand that the Rock Record is a scandal-sheet newspaper, like the late and much-lamented News of the World, recording the exciting stuff, and leaving most of the quotidian tedium unrecorded. But when it comes to humans and the atmosphere, Lyell’s dictum holds true. As Terrence Gerlach of the Cascades Volcano Observatory writes: “humanity’s ceaseless emissions release an amount of CO2 comparable to the 0.01 gigaton of the 1980 Mount St Helens paroxysm every 2.5 hours, and the 0.05 gigaton of the 1991 Mount Pinatubo paroxysm every 12.5 hours”.

So let us not hear any more of this nonsense. A dog did not eat your homework, and the nasty smell in the room wasn’t previously inside the cat. It’s time to own the gas.