Humans Spew More Carbon Dioxide than All of Earth's Volcanoes

Stephanie Pappas, LiveScience Yahoo News 15 Jun 11;

Explosive volcanic eruptions might be attention grabbing, but a new review of research finds that their environmental impact pales in comparison to human activities. According to the research, humans put out the same amount of carbon dioxide in three to five days that all of the volcanoes on Earth put out in one year.

"Anthropogenic carbon dioxide emissions dwarf global volcanic carbon dioxide emissions," study researcher Terrance Gerlach, of the U.S. Geological Survey, said in a statement. Carbon dioxide, or CO2, is the main greenhouse gas responsible for climate change.

Gerlach crunched the carbon dioxide numbers from earlier studies of volcanic output, finding a range of 0.13 to 0.44 billion metric tons, or gigatons, of CO2 per year. In comparison, the estimated rate of human carbon dioxide emissions for 2010 alone is 35 billion metric tons.

For instance, here are a few carbon-emitting human activities and their carbon-dioxide outputs:

Land-use changes: 3.4 gigatons per year
Light-duty vehicles (mainly cars and pickup trucks): 3.0 gigatons per year
Cement production: 1.4 gigatons per year

Present-day human carbon emissions could even exceed the CO2 output of several supervolcano eruptions, including the giant eruption that will eventually occur at Yellowstone National Park, Gerlach wrote in the American Geophysical Union's newsweekly Eos. These mega-eruptions are very rare, with the last one occurring 74,000 years ago in Indonesia.

In fact, to scale up volcanic emissions to an equivalent of what we release would require the release of more than 200 cubic miles (850 cubic kilometers) of magma per year, the researchers calculate. For comparison, Lake Ontario holds about 393 cubic miles (1,640 cubic km) of water.