NCPA - National Center for Policy Analysis

Debate Shifts On "Global Warming" Culprits

October 6, 2000

Carbon dioxide (CO2) is not the only greenhouse gas trapping heat in the earth's atmosphere -- and some scientists suggest that reducing the concentration of CO2 in the atmosphere may not even be the most important factor in slowing global warming caused by human activity. They say that concentrating on reducing more potent greenhouse gases such as methane, ozone and soot might yield greater -- and more immediate -- climate benefits than reducing CO2 emissions.

The major proponent of this strategy is James E. Hansen who, along with a team of colleagues at the National Aeronautics and Space Administration's Goddard Institute for Space Studies, published a paper in August entitled "Global Warming in the 21st Century: An Alternative Scenario."

Although the concentration of these other greenhouse gases in the atmosphere is much lower than CO2, the Global Warming Potential (GWP) -- a measure of relative radiative effect -- of these gases and particulates is far greater. Expressed as the ratio of global warming from one unit mass of a gas to that of one unit mass of carbon dioxide over 100 years:

  • The GWP of methane is 21, meaning it is that many times more potent a greenhouse gas than CO2.
  • Nitrous Oxide (N2O) -- "laughing gas" -- is 310 times more potent than CO2.
  • CFC-12, a refrigerant, is 8,100 times more potent.
  • And Sulfur Hexafluoride (SF6), used in asthma inhalers, is 23,900 times more potent.

It may be more efficient, and politically and economically palatable, to find replacements for industrial and consumer uses for these chemicals, says Hansen, than to substantially reduce CO2, which is a byproduct of burning fossil fuels.

Source: Andrew C. Revkin, "Debate Rises Over a Quick(er) Climate Fix," New York Times, October 3, 2000.


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