|Total greenhouse gas emissions (CO2, CH4, N20 and HFCs) allocated to passenger cars and light trucks, 1990-2007. Click to enlarge.|
Overall greenhouse gas emissions in the US during 2007 increased by 1.4% from the previous year to 7,125.2 Tg CO2 Eq., according to the annual Inventory of US Greenhouse Gas Emissions and Sinks: 1990-2007 draft report released by the Environmental Protection Agency (EPA). Overall, total US emissions have risen by 17% from 1990 to 2007. The report will be open for public comment for 30 days after the Federal Register notice is published.
According to the draft report, this trend was due primarily to (1) cooler winter and warmer summer conditions in 2007 than in 2006 which increased the demand for heating fuels and contributed to the increase in the demand for electricity, (2) increased consumption of fossil fuels to generate electricity and (3) a significant decrease (14.2%) in hydropower generation used to meet this demand.
CO2 emitted from fossil fuel combustion represents the largest share of US total greenhouse gas emissions. In 2007, CO2 emissions from fossil fuel combustion were 5,747.6 Tg CO2 Eq., up 1.8% from 2006 and 22% above such emissions in 1990.
When electricity-related emissions are distributed to economic end-use sectors, transportation activities accounted for 2,000.1 Tg CO2 Eq., or 28% of US greenhouse gas emissions in 2007. That represents a slight (0.06%) increase from 2006 and is still down 0.17% from the peak in 2005 of 2,003.6 Tg.
The largest sources of transportation GHGs in 2007 were passenger cars (33%), light duty trucks (28%), freight trucks (21%) and commercial aircraft (8%). These figures include direct emissions from fossil fuel combustion, as well as HFC emissions from mobile air conditioners and refrigerated transport allocated to these vehicle types.
Fuel purchased in the US for international aircraft and marine travel accounted for an additional 108.8 Tg CO2 in 2007; these emissions are recorded as international bunkers and are not included in US totals according to UNFCCC reporting protocols.
Total greenhouse gas emissions from passenger cars and light trucks dropped to 1,226.3 Tg CO2 Eq. in 2007, down 0.74% from 2006.
CO2 from fossil fuel combustion for transportation has increased by 29% from 1990 to 2007. This rise in CO2 emissions, combined with an increase in HFCs from virtually no emissions in 1990 to 67.0 Tg CO2 Eq. in 2007, led to an increase in overall emissions from transportation activities of 28%. This increase is due largely to increased vehicle miles travelled (VMT) and the stagnation of fuel efficiency across the US vehicle fleet. VMT by light-duty motor vehicles increased 40% from 1990 to 2007, as a result of a confluence of factors.
The inventory tracks annual greenhouse gas emissions from 1990 to 2007 at the national level. The gases covered by this inventory include carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride. The inventory also calculates carbon dioxide emissions that are removed from the atmosphere by sinks.
This annual report is prepared by EPA in collaboration with experts from multiple federal agencies. After responding to public comments, the US government will submit the final inventory report to the Secretariat of the United Nations Framework Convention on Climate Change (UNFCCC).
The report will fulfill the annual requirement of the UNFCCC international treaty, ratified by the United States in 1992, which sets an overall framework for intergovernmental efforts to tackle the challenge posed by climate change.