What Causes More Climate Change - Humans Or Volcanic Eruptions?

Stromboli, one of the most active volcanoes in the world, backlit by a full moon. Rainer Albiez/Shutterstock

Robin Andrews 22 Jul 2017, 17:42

We’ve noticed that under a lot of our climate change articles, a common argument used by deniers of the science keeps rearing its ugly head. Namely, volcanic eruptions dump more carbon dioxide into the atmosphere than humans ever could, so our own greenhouse gas (GHG) emissions have almost no influence on the climate whatsoever.

A similar argument posits that volcanic eruptions produce so much reflective sulfur dioxide that when one erupts badly enough, it’ll cool the climate so much that all our GHGs will be canceled out in the future. Both of these arguments hold zero water. They are bullshit, and here’s your primer explaining why.

Let’s look at the former argument first, the idea that volcanoes are better producers of carbon dioxide than humanity.

Firstly, yes, it’s true that volcanoes produce more carbon dioxide than most other processes. They actually release plenty of gases – technically known as volatiles – whose concentrations depend on the style of the eruption (sudden and explosive versus prolonged and calm) and the geochemistry of the magma source.

The most common gases released are water vapor, carbon dioxide, carbon monoxide, hydrogen sulfide compounds, sulphur dioxide, and a handful of others.

Humans will always produce more carbon dioxide per year than volcanoes. cornfield/Shutterstock

Climate skeptics often point to water vapor being the most important GHG, but this is normally used to suggest that carbon dioxide isn’t a problem. Water vapor does trap solar radiation into the atmosphere, but its concentration directly depends on the temperature. Warmer worlds have more water vapor in the atmosphere, and colder worlds have less. We cannot control this.

Carbon dioxide, however, we do control. Although not the most effective trapper of heat, it is still pretty good at it; its cumulative lifetime up there is around 20 to 200 years. This makes it the most important GHG.

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