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Which is the bigger polluter – humans or volcanoes?

EarthTalk: If you said ‘volcanoes,’ guess again. Here’s why.

Mt. Pinatubo: This aerial view shows the crater formed by the catastrophic eruption on the Philippine island of Luzon on June 15, 1991. Some 900 died, with 42,000 homes destroyed.


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Q: Could it really be true that a single large volcanic eruption launches more greenhouse gases into the atmosphere than the amount generated by all of humanity over history?
Steve Schlemmer, London

A: The argument that human-caused carbon emissions are merely a drop in the bucket compared with greenhouse gases generated by volcanoes has been making its way around the rumor mill for years. And while it may sound plausible, the science just doesn’t add up.

According to the US Geological Survey, all the world’s volcanoes – on land and undersea – generate about 200 million tons of carbon dioxide (CO2) annually, while our automotive and industrial activities create some 24 billion tons of CO2 emissions every year worldwide. Those facts speak for themselves: Greenhouse gas emissions from volcanoes are less than 1 percent of those generated by today’s human endeavors.

Another indication that human emissions dwarf those of volcanoes is the fact that atmospheric CO2 levels, as measured by sampling stations around the world set up by the federally funded Carbon Dioxide Information Analysis Center, have gone up consistently year after year regardless of whether or not there were major volcanic eruptions in specific years.


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