CO2 emissions from fossil-fuel combustion in the US increased 3.7% between 2009-2010, the largest single-year increase seen in a 21-year period. The year-on-year rise is tied to increased economic activity, warmer summer temperatures that pushed up energy demand and a higher CO2 intensity of the fuels being combusted, the Environmental Protection Agency (EPA) noted in its draft 17th Annual Greenhouse Gas Inventory. Electricity generation made up about 39% of total US CO2 emissions in 2010 and represented about 42% of energy-related CO2 emissions. CO2 emissions from coal-generated electricity increased by 5% from 2009 to 2010 and represented 95% of total CO2 emissions from the combustion of coal. Emissions from natural gas-generated electricity increased of 7.3%.
The combustion of petroleum, accounted for 38% of total energy-related CO2 emissions, the majority coming from the transportation sector, according to the report. The specific breakdown of emissions from the transportation sector and mobile fossil fuel combustion is still being updated with 2010 data but EPA said personal vehicle use made up 65% of the sector's emissions.
The number of cooling degree days in 2010 was 19% higher than the year prior, and 17% above normal, according to EPA. A 6% drop in hydropower generation also contributed to higher emissions from the electric sector.
Since 1990, US CO2 emissions from fossil-fuel combustion are up 14%. Total US greenhouse gas emissions are up 11% over the 21-year period, and increased by 3.3% between 2009-2010.