Reliable News and Analysis in Climate Science
SUMMER 2002 Volume 1 Number 2
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New US Statement on Its Role in Climate Change

White House agrees temperature change "likely due mostly to human activity"



Although the United States refused to sign the Kyoto Protocol, it had earlier signed the 1992 U.N. Framework Convention on Climate Change. Each member nation of the Framework Convention is required to report its greenhouse gas emissions and trends over time. The White House just submitted the Third US National Communication on Climate Change covering the 1990s; it is available through the Environmental Protection Agency at www.epa.gov/globalwarming/publications/car/

Climate Change Science



The Administration let stand the conclusion of the National Research Council in its 2001 report, Climate Change Science. As we reported in our March issue, the Council said, "Greenhouse gases are accumulating in Earth's atmosphere as a result of human activities, causing global mean surface air temperature and subsurface ocean temperature to rise. While the changes observed over the last several decades are likely due mostly to human activities, we cannot rule out that some significant part is also a reflection of natural variability." (Emphasis ours)

Trends in Emissions



The report covered the period 1990-1999, but we have updated the figures to 2000 with data from EPA. The US economy emitted 14% more Greenhouse gases at the end of the decade than at the start, an increase of 1.3% per year. Carbon dioxide accounted for 83% of these emissions and grew at 17% per decade. The overwhelming source of CO2 (96% of it) was the combustion of fossil fuels.

Other greenhouse gases are compared with carbon dioxide by converting their emissions from tons into tons of "equivalent CO2". Each gas has a unique factor (a "global warming potential") indicating how much one kilogram of gas can affect the heat balance of Earth. Methane has a factor 21 times larger than CO2 because methane is so much more active as a greenhouse gas. As measured in equivalent CO2, methane now contributes to 9% of the greenhouse gas emissions, but these emissions have fallen by 6% over the decade. The largest source of methane is landfill gases. Nitrous oxide now amounts to 6% of the emissions and its contribution has increased 10% over the ten years. Most of the gas results from the application of nitrogen fertilizers to soils.

An increase of forest area and other changes in land use have removed some carbon dioxide from the atmosphere. This report treats these so-called "carbon sinks" as a credit amounting to 13% of the gross total emissions. Because of the credit, the report speaks of gross emissions and net emissions of greenhouse gases.

Policy Actions



Policies center around a continuation of existing programs plus new, primarily voluntary efforts:

  • Standards for efficiency of residential appliances. Four new standards (for central air conditioners, water heaters, fluorescent lights, and washing machines) are now pending
  • Continuing the Energy STAR program for homes and office buildings
  • Federal/Industry partnerships have reduced the emissions of methane, the number-two greenhouse gas. These will hold down the emissions below 1990 levels through the year 2010
  • Other programs focus on reducing the emissions of those greenhouse gases with the highest "global warming potential" (these are not CO2).
  • More partnerships with State and local governments. To date, there are 41 state inventories of greenhouse gases, 27 state action plans, and 110 cities and counties with either one or the other.

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