Volcanic Gases and Climate Change Overview [USGS]
Volcanic versus anthropogenic CO2 emissions
Do the Earth’s volcanoes emit more CO2 than human activities? Research findings indicate that the answer to this frequently asked question is a clear and unequivocal, “No.” Human activities, responsible for a projected 35 billion metric tons (gigatons) of CO2 emissions in 2010 (Friedlingstein et al., 2010), release an amount of CO2 that dwarfs the annual CO2 emissions of all the world’s degassing subaerial and submarine volcanoes (Gerlach, 2011).
The published estimates of the global CO2 emission rate for all degassing subaerial (on land) and submarine volcanoes lie in a range from 0.13 gigaton to 0.44 gigaton per year (Gerlach, 1991; Varekamp et al., 1992; Allard, 1992; Sano and Williams, 1996; Marty and Tolstikhin, 1998). The preferred global estimates of the authors of these studies range from about 0.15 to 0.26 gigaton per year.
The 35-gigaton projected anthropogenic CO2 emission for 2010 is about 80 to 270 times larger than the respective maximum and minimum annual global volcanic CO2 emission estimates. It is 135 times larger than the highest preferred global volcanic CO2 estimate of 0.26 gigaton per year (Marty and Tolstikhin, 1998).
In recent times, about 70 volcanoes are normally active each year on the Earth’s subaerial terrain. One of these is Kīlauea volcano in Hawaii, which has an annual baseline CO2 output of about 0.0031 gigatons per year [Gerlach et al., 2002]. It would take a huge addition of volcanoes to the subaerial landscape—the equivalent of an extra 11,200 Kīlauea volcanoes—to scale up the global volcanic CO2 emission rate to the anthropogenic CO2 emission rate. Similarly, scaling up the volcanic rate to the current anthropogenic rate by adding more submarine volcanoes would require an addition of about 360 more mid-ocean ridge systems to the sea floor, based on mid-ocean ridge CO2 estimates of Marty and Tolstikhin (1998).
There continues to be efforts to reduce uncertainties and improve estimates of present-day global volcanic CO2 emissions, but there is little doubt among volcanic gas scientists that the anthropogenic CO2 emissions dwarf global volcanic CO2 emissions.
For additional information about this subject, please read the American Geophysical Union's Eos article "
Volcanic Versus Anthropogenic Carbon Dioxide" written by USGS scientist Terrence M. Gerlach.
Yearly CO2 emitters
Billion metric tons per year (Gt/y)
Global volcanic emissions (highest preferred estimate) 0.26
Anthropogenic CO2 in 2010 (projected) 35.0
Light-duty vehicles (cars/trucks) 3.0
Approximately 24 1000-megawatt coal-fired power stations * 0.22
Argentina 0.22
Pakistan 0.18
Saudi Arabia 0.44
CO2 emission events
Mount St. Helens, 18 May 1980 0.01 Gt
Mount Pinatubo, 15 June 1991 0.05 Gt
Number of Pinatubo-equivalent eruptions equal to annual anthropogenic CO2 700
Number of Mount St. Helens-equivalent eruptions equal to annual anthropogenic CO2 3500
2010 anthropogenic CO2 multiplier (ACM)**
135 1900 ACM
18 1950 ACM 38
Number of days for anthropogenic CO2 to equal a year's worth of global volcanism 2.7
* Equal to 2% of the world's coal-fired electricity-generating capacity.
**Ratio of annual anthropogenic CO2 (35 Gt) to maximum preferred estimate for annual volcanic CO2.
Facebook
Twitter