Science Questions

How much pollution does a volcano produce? I’ve heard that a volcanoes spew out as much pollution as all the cars that have ever been put on Earth combined but how much pollution does a volcano produce when it erupts? Darwin Teague

We asked our guest Marie Edmonds:

Marie- This is a very good question and it gives me an opportunity to dispel some of the myths about volcanoes and global warming and pollution. Volcanoes emit CO2 and SO2: carbon dioxide and sulphur dioxide are the main gases that might be construed to cause global warming or pollution. Volcanoes emit around 100,000,000 tonnes of CO2 a year. Compare that to man-made emissions of CO2 which comes to about 10,000,000,000 tonnes of CO2 per year. So volcanoes emit around 1/100^th of CO2 that we do and are therefore insignificant in terms of global warming. Sulphur dioxide on the other hand, volcanoes emit around a tenth of the anthropogenic emissions of SO2. That forms regional smog.

Chris- Isn’t there a benefit of sulphur dioxide in that it reflects heat back in to space? In fact it cools down the Earth so volcanoes are quite good in that respect because they keep us cooler than we otherwise would be.

Marie- Yes. There has been some research in the last few years that suggests very large eruptions such as Pinatubo in 1991. That eruption emitted about 20 megatonnes of SO2 into the stratosphere. Eruptions such as those which happen once every decade in fact have slowed down global warming a little bit. Without those eruptions we’d actually see the effects of global warming much more now than we do.

June 2008