Population World Population: CO2 ppm World Carbon: 390 ppm

Tuesday, 4 October 2011

Volcanic vs. Anthropogenic CO2

Guest Commentary by Terry Gerlach*

TV screen images of erupting and exploding volcanoes spewing forth emissions are typically spectacular, awesome, and vividly suggestive of huge additions of gas to the atmosphere. By comparison, the smokestack and exhaust pipe venting of anthropogenic emissions is comparatively unexciting, unimpressive, and commonplace. Consequently, it easy to get traction with the general public for claims that volcanic CO2 emissions are far greater than those of human activities, or that the CO2 released in some recent or ongoing eruption exceeds anthropogenic releases in all of human history, or that the threat of a future super-eruption makes concerns about our carbon footprint laughable. The evidence from volcanology, however, does not support these claims.

Volcanic plume ** V Fossil fuel plumes**

My article “Volcanic Versus Anthropogenic Carbon Dioxide” appeared in the June 14 issue of the American Geophysical Union’s publication Eos and addresses the widespread mis-perception in the media, the blogosphere, and much of the climate skeptic literature that volcanic CO2 emissions greatly exceed anthropogenic CO2 emissions. I wrote the article to provide a comprehensive overview of the topic using only published peer-reviewed data with a minimum of technical jargon for a broad spectrum of Earth science researchers and educators, students, policy makers, the media, and the general public. AGU has made the article public; anyone can download a copy. There is also an Eos online supplement, although I have a better formatted pdf version that is available upon request.

The bottom line? Annual anthropogenic CO2 emissions exceed annual volcanic CO2 by two orders of magnitude, and probably exceed the CO2 output of one or more super-eruptions***. Thus there is no scientific basis for using volcanic CO2 emissions as an excuse for failing to manage humanity’s carbon footprint.

*Terry Gerlach is retired from the U.S. Geological Survey where he was a volcanic gas geochemist.The views expressed are his own.
** Yes we are aware that CO2 is colorless and that the plumes in the figures are mostly steam. – Eds.
***Super-eruptions are extremely rare, with recurrence intervals of 100,000–200,000 years; none have occurred historically, the most recent examples being Indonesia’s Toba volcano, which erupted 74,000 years ago, and the United States’ Yellowstone caldera, which erupted 2 million years ago.

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