Compiled By Jill Jusko Total U.S. greenhouse gas emissions fell by 1.2% to 1,883 million metric tons in 2001, led by a decrease in carbon dioxide, says the U.S. Department of Energy's statistics agency. This decrease is in contrast to an average annual growth rate of 1.3% from 1990 to 2000 and is only the second decline since 1991, when total emissions dropped by 0.6%. While the drop in greenhouse gas emissions may be positive news, the contributing factors to the decline are less than pleasing. The decrease in carbon dioxide, which accounts for more than 80% of U.S. greenhouse gas emissions, can be attributed to a slowing economy, reports the Energy Information Administration (EIA). More specifically, the statistics agency cited contributing factors of: a reduction in economic growth from 3.8% in 2000 to 0.3% in 2001; a 4.4% reduction in manufacturing output that lowered industrial emissions; warmer winter weather that decreased demand for heating fuels; and lowered electricity demand that also resulted from a slowing economy. Methane emissions, the second largest contributor to greenhouse gas emissions, are estimated to have declined by 1.1% in 2001 and are down by 11.6% since 1990. Emissions from human-made gases, such as hydroflurocarbons, decreased by 7.7% between 2000 and 2001 but are up 24% since 1990, the EIA reports.