Thursday, May 18, 2006


The Other 50%

I just returned from beautiful Gunnison, Colorado, where the Rocky Mountain section of GSA is holding its annual meeting. I attended a talk in the Springs and Groundwater session by Laura Crossey from the U. of New Mexico. She spoke about Carbon Dioxide degassing from springs in the Colorado Plateau area. While not the major thrust of her talk, Dr. Crossey pointed out that commonly accepted models of natural CO2 emissions estimate that on the order of 1012 moles of CO2 are released each year along the mid-ocean ridges (the so-called Black Smokers) and an additional 1012 moles of CO2 are released from volcanoes. Thus, each of these sources is thought to provide about 50% of natural CO2 emissions. Dr. Crossey and her colleagues think that they may have discovered "the other 50%." Based on their studies of springs in the Colorado Plateau, Crossey et al. estimate that worldwide CO2 emissions from degassing of springs probably reach the same order of magnitude as emissions from either volcanoes or mid-ocean ridges (i.e., degassing of springs contributes about 1012 moles of CO2 each year). I should also note that "emissions" in this context refers to new CO2 that is being added to the carbon cycle.

For comparison, in 2002 (the latest data I could find) worldwide anthropogenic CO2 emissionss is on the order of 1014 moles per year. That is a whopping 100 times more CO2 entering the atmosphere from human activity than from natural degassing. I'm not one to rant about global warming, but according to these data the old argument that more (new) CO2 is entering the atmosphere through natural processes than through human activity has apparently been put to rest. Not only that, but according to US Dept. of Energy data you would have to go back to before the industrial revolution (1850's) to find a time when natural CO2 emissions exceeded anthropogenic emissions. Just a little food for thought.

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