A reader sent me this. Here’s the relevant bit:

CO2 Emissions in US Unchanged U.S. carbon dioxide emissions from burning fossil fuels increased by 0.1 percent in 2005, from 5,903 million metric tons of carbon dioxide (MMTCO2) in 2004 to 5,909 MMTCO2 in 2005, according to preliminary estimates released today by the Energy Information Administration (EIA). The 2005 emissions increase was the third smallest during the 1990 to 2005 period, exceeding only the emissions declines recorded in 1991 and 2001… …U.S. carbon dioxide intensity (energy-related carbon dioxide emissions per unit of economic output) fell by 3.3 percent in 2005. From 1990 to 2005, the carbon dioxide intensity of the economy fell by 24.3 percent. By 2004 (the latest year of data for all greenhouse gases), carbon dioxide intensity had fallen by 21.8 percent and emissions of total greenhouse gases per dollar of GDP had fallen by 23.4 percent. The 3.3-percent drop in carbon dioxide intensity of the economy in 2005 is greater than the average reduction of 1.8 percent per year experienced since 1990.

Update: From a reader:

Note that the years when CO2 emissions declined were 1991 and 2001 — both
recession years.