EPA Issues Final Inventory of Greenhouse Emissions, Still Shows Reductions
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Greenhouse gas emissions in the United States dropped by a somewhat lower fraction than earlier reported, according to final estimates released this week by the U.S. Environmental Protection Agency.
However, the annual Inventory of Greenhouse Gas Emissions and Sinks still showed a 1.1 percent drop between 2005 and 2006, compared to a draft report’s estimate earlier this year of a 1.5 percent decline (latest report can be accessed here; EPA press statement here). It also indicated that previous years’ emissions were a bit lower than had been previously estimated.
Both versions of the report also concluded that a variety of factors, including increased use of natural gas and renewable power sources, warmer winter weather and rising fuel prices contributed to the decline (see previous Climate Law Update story here).
The agency recalculated some of the base figures used in the report, which produced estimates lower than those previously reported. Those changes also helped narrow some of the gaps between the years. For instance, the earlier draft report showed total emissions in 2005 were equivalent to 7.3 billion metric tons of carbon dioxide, dropping to just more than 7.2 billion in 2006, a difference of about 112 million tons. In the revised report, those figures were about 7.1 billion and 7 billion, respectively, a difference of approximately 75 million tons.
In an e-mail to Climate Law Update, EPA spokeswoman Roxanne Smith said that between the issuance of the draft and final reports, "recalculations were made to incorporate additional revised data." When that new information is incorporated, errors are addressed or "improved methodologies are adopted," she said. Those can then lead to changes for all years in the inventory, which spans 1990 to 2006, Smith added.
The inventory includes estimates of carbon dioxide, methane, nitrous oxide, hydroflourocarbons, perflourocarbons and sulfur hexafluoride. It also calculates emissions removed from the atmosphere by so-called sinks, such as forests, vegetation and soils.
According to the latest report, carbon dioxide emissions from fossil fuel combustion declined about 1.6 percent between the two years, compared to the draft document’s estimated 1.9 percent drop. Overall estimates of carbon dioxide emissions in 2006 remained unchanged in both reports, while the revised version showed a slightly lower estimate for 2005.
In addition, the newest report, which is submitted to the Secretariat of the United Nations Framework Convention on Climate Change, estimated that overall emissions of the six main greenhouse gases have grown by 14.7 percent from 1990 to 2006. The earlier report had that figure at 14.1 percent. The United Nations body monitors the Kyoto Protocol.
One of the largest tonnage differences between the draft and final reports this year appeared to be a drop in the estimate of nitrous oxide. The earlier report estimated emissions of that gas at more than 530 million tons for each of the years, while the latest document estimated the amount at 370.1 million tons in 2005 and less than 367 million tons in 2006. A portion of the report charting annual changes to the calculations noted that revisions, including incorporating state-by-state data for nitrogen fertilizer use, had produced about a 27 percent annual decrease in the estimates for nitrous oxide emissions from soil management on farms.
(Pictured: General Electric advanced gas turbine, U.S. Department of Energy photo)
