Greenhouse gas emissions in the US totaled 6,702,000 million metric tons of carbon dioxide equivalent in 2011, a 1.6 percent reduction from the previous year, according to an annual report by the EPA.
The drop can be attributed to multiple factors including reduced emissions from electricity generation, improvements in fuel efficiency in vehicles with reductions in miles traveled and year-to-year changes in the prevailing weather, the EPA says in its report.
The Inventory of US Greenhouse Gas Emissions and Sinks: 1990-2011 tracks annual GHG emissions at the national level and presents historical emissions. The inventory, which is submitted each year to the Secretariat of the United Nations Framework Convention on Climate Change, also calculates CO2 emissions that are removed from the atmosphere through the uptake of carbon by forests, vegetation, soils and other natural processes called carbon “sinks.”
GHG emissions in 2011 were 6.9 percent lower than 2005 levels, according to the report.
Electricity production generated 33 percent of greenhouse gas emissions in 2011, the largest share of any source. Power plant emissions are primarily due to the burning of fossil fuels, such as coal and natural gas.
Transportation accounted for the next largest share, generating 28 percent of GHG emissions. Industry produced 20 percent of 2011 GHGs, which came primarily from burning fossil fuels for energy as well as emissions from certain chemical reactions needed to produce goods from raw materials.
Commercial and residential generated 11 percent and agriculture produced 8 percent of 2011 emissions, according to the report. Managed forests and other lands, which absorb more CO2 from the atmosphere than they emit, offset 14 percent of 2011 greenhouse gas emissions.
The EPA announced on Friday that it will delay finalizing regulations that limit GHGs from new power plants, and would rewrite the rules to address concerns raised by the electric industry.
The agency would not say when the new standards would be issued. The rules proposed last March would have limited CO2 emissions to 1,000 pounds per MWh. They were scheduled to be finalized last Saturday; last week, top White House climate adviser Heather Zichal said they would be enacted in the “not-too-distant future.”