Growth rate slows for U.S. greenhouse gas emissions

U.S. emissions of greenhouse gases increased 1.4% in 1997 from the prior year, about half the rate of increase seen in 1996, reported the U.S. Energy Information Administration.

These emissions, totaling 1.791 billion metric tons of carbon equivalent (tce), were nearly 10% higher than the 1990 level, the base year for international negotiations to limit greenhouse gas emissions (see related story, this page).

EIA said the rate of growth in 1997 is a return to the average experienced for the rest of the decade, following a weather-induced increase in 1996 of 2.8%.

The EIA report said that greenhouse gas emissions continue to grow less rapidly than the U.S. economy, which grew 3.8% in 1997 from the prior year.

U.S. carbon dioxide emissions increased by 1.5%, or 22 million tce, most of which increase-19 million tce-came from burning fossil fuels. U.S. CO₂ emissions from all sources in 1997 were 1.501 billion tce, or 84% of total greenhouse gas emissions.

Emissions growth for the gases other than CO₂ was relatively flat, increasing by 0.7%, or 2 million tons. Emissions of these gases were about 290 million tce in 1997, or 16% of total greenhouse gas emissions.

Breakouts

EIA said of the 19 million tce increase in energy-related CO₂ emissions in 1997, 11 million tce came from the commercial sector.

Industrial sector emissions rose 5 million tce, indicating a continuation in a shift in the U.S. economy from more energy-intensive goods to less energy-intensive services.

For the first time in 6 years, the transportation sector made little contribution to U.S. CO₂ emissions growth.

The next largest contributor of total greenhouse gas emissions, methane, accounts for 9% of total greenhouse gas emissions. Methane emissions were flat in 1997 at 167 million tce. Since 1990, U.S. methane emissions have dropped by about 3.5%.

Nitrogen oxide emissions, which account for about 5% of total greenhouse gas emissions, dropped by 1 million tce to 85 million tce in 1997.

Emission levels of human-made gases such as hydrofluorocarbons, perfluorocarbons, and sulfur hexaflouride are very small (only 2% of total emissions), but their global warming potential is high.

This category experienced a 3 million tce increase in 1997 from the prior year, to 38 million tce.