NCPA - National Center for Policy Analysis

Do Catalytic Converters Cause Global Warming?

December 16, 1998

The Environmental Protection Agency is gearing up the next step in its war against automobiles, say critics. It released a report last summer that claims nitrous oxide (N2O) from the catalytic converters that clean the tailpipe emissions of automobiles is contributing to global warming. Global warming is the theory that so-called greenhouse gases produced by human activities are affecting the climate. The principal greenhouse gases are water vapor and carbon dioxide (CO2).

Experts point out that compared to the total amount of greenhouse gases, the amount of N2O emitted from car tailpipes is so insignificant it couldn't possibly affect the global climate.

  • Worldwide, the total annual output of greenhouse gases is around 157.1 billion metric tons, according to the United Nations Intergovernmental Panel on Global Climate Change.
  • Mankind produces just 7.1 billion metric tons of the total -- with the rest coming from natural sources, such as volcanic eruptions, the evaporation of sea water and the decay of organic matter.
  • The U.S. produces 1.442 billion tons of greenhouse gases annually from human activities.
  • Of the U.S. output, the EPA claims 280.7 million metric tons comes from the operation of motor vehicles -- mostly water vapor and carbon dioxide (CO2), thanks to the catalytic converters.
  • It also estimates that N2O from all sources is 7.2 percent of Americans' total output of greenhouse gases, or 103.8 million metric tons.

Thus the N2O from the tailpipes of American cars is at most 0.06 percent of total greenhouse gases produced in the world each year -- and EPA critics say it may be much less, since the EPA has a record of inaccuracy.

Ironically, experts say catalytic converters and other technological advances are responsible for much of the improvement in air quality over the last 30 years.

Source: Eric Peters, "A Catalytic Con Job," Investor's Business Daily, December 16, 1998.


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