Global Warming Basics

According to many Skeptics, volcanoes release more Carbon Dioxide into the atmosphere than humans therefore, any human release of the gas is trivial and does not contribute to Global Warming. However, according to the United States Geological Survey (USGS), humans emit much more CO₂ than volcanoes. They state:

Which emits more carbon dioxide (CO2): Earth’s volcanoes or human activities? Research findings indicate unequivocally that the answer to this frequently asked question is human activities. However, most people, including some Earth scientists working in fields outside volcanology, are surprised by this answer. The climate change debate has revived and reinforced the belief, widespread among climate skeptics, that volcanoes emit more CO2 than human activities [Gerlach, 2010; Plimer, 2009]. In fact, present-day volcanoes emit relatively modest amounts of CO₂, about as much annually as states like Florida, Michigan, and Ohio. – EOS, Transactions, American Geophysical Union, Volume 92, Number 24,  June 14, 2011 Pages 201-208

Figure 1: The proportion of volcanic emissions of CO2 (Small gray illustration) compared to human emissions (Large gray illustration). Courtesy of Skeptical Science.

Also, this article in Scientific American says:

According to the U.S. Geological Survey (USGS), the world’s volcanoes, both on land and undersea, generate about 200 million tons of carbon dioxide (CO2) annually, while our automotive and industrial activities cause some 24 billion tons of CO2 emissions every year worldwide. Despite the arguments to the contrary, the facts speak for themselves: Greenhouse gas emissions from volcanoes comprise less than one percent of those generated by today’s human endeavors.