Volcanoes, CO2 and Temperatures

A friend has prompted me to post for reference a couple illustrations I've created for www.skepticalscience.com on estimates of emissions of CO2 by volcanoes. It is a common belief that volcanic activity produces more atmospheric CO2 that human activity, however, research shows that in the modern era, volcanoes haven't been active enough to account for the steady rise in CO2.

The first chart compares surface temperatures by the Goddard Institute for Space Studies with atmospheric CO2 and stratospheric optical thickness, which is used as a proxy for volcanic activity.

The second illustration summarizes the conclusion of Terry Gerlach of USGS publishing in the Transactions of the American Geophysical Union: Volcanic vs Anthropogenic Carbon Dioxide, EOS, 14 June 2011).

In the above diagram, the area of the clouds correspond to the emissions of each source.
jg