The US Energy Information Administration (EIA) released yesterday the 2009 data on energy-related CO2 emissions in the United States. As Joe Romm notes, annual emissions are down by almost 10 percent from 2005. In 2009 alone, emissions decreased by 7 percent.

Source: EIA 2010

What is most interesting about these data are the reasons for this decline.

1) Approximately one third of the decrease can be attributed to a decrease in GDP. This is the direct effect of the recession, and it will not last if the economy recovers.

2) Another third stems from a decrease in the energy intensity of the economy. Energy use decreased dramatically both in transportation and industrial production. To me, it is not clear how much of this decrease can be attributed to the recession. On the one hand, record energy prices in 2008 surely induced efficiency improvements, especially in industrial production. These improvements will have a lasting effect. On the other hand, the EIA data show that the recession hit hard many energy-intensive sectors of the economy, such as primary metals production  and nonmetallic minerals. Similarly, transportation emissions continued to decrease even after energy prices decreased.

3) The final third comes from changes in carbon intensity. While the recession reduced coal and oil consumption, it had a modest effect on natural gas while renewable energy production continued to grow. Some of the robust growth in renewable energy is from the green stimulus implemented by the Obama administration.

Source: EIA 2010

The EIA conjectures that both energy intensity and carbon intensity continue to decrease in the United States, but GDP will increase with economic recovery. The relative strength of these countervailing effects will depend on energy legislation, both in the states and at the federal level.