That's a remarkable change from what has been occurring in the United States for nearly two decades. Total GHG emissions grew at an average annual rate of 0.7 percent every year since 1990. That is until 2008 came along.
The decrease in total emissions was largely the result of a drop in carbon dioxide emissions, the report said. And the cause was three-fold: higher energy prices, which led to drop in petroleum use; lower demand for electricity; and finally, an economy that contracted in three of four quarters in 2008 and caused demand to fall in nearly every area except the commercial sector.
Emissions of energy-related carbon dioxide fell by 2.9 percent in 2008. Again, a reversal from previous years when C02 emissions used to rise an average 1 percent a year between 1990 and 2007. Isolate the oil-related emissions -- which fell 5.9 percent -- and the story becomes clearer.
Energy-related C02 emissions make up 81 percent of total U.S. greenhouse gas emissions with petroleum taking the biggest piece of the emissions pie. Petroleum contributes 42 percent and coal is the second-largest fossil fuel contributor at 37 percent.
Recessions do more than simply lower demand and use of petroleum, coal and natural gas -- all of which curbed emissions in 2008. It can also curb advancements in emissions-cutting technology.
The Environmental Protection Agency reported earlier this week an increase in fuel efficiency -- and a decrease in C02 emissions in new cars and light trucks -- for the fifth consecutive year. But progress slowed considerably during the recession, cleantech blogger John Addision noted. the average fuel economy value was 21 miles per gallon in 2001 and EPA projects a small improvement this year to 21.1 mpg.