Department of Numbers

US Greenhouse Gas Emissions

Posted Sunday, May 01 2011

Last month I pointed out that the EPA's annual US greenhouse gas (GHG) emissions inventory report showed that US emissions in 2009 fell by 15% since 2000. I finally got around to digging into the report a little more and it turns out the decline is actually 14% and only on a net basis. Net emissions are total emissions less carbon sinks from changes in things like land use (e.g. uncut or unburned forests). The table below shows net emissions since 1990 as well as the total change since 1990 and 2000.

Net Emissions: Sources - Sinks

Year Net Emissions (Tg)1 Total Change Since 1990 Total Change Since 2000
1990 5,320.3
2000 6,536.1 22.85%
2005 6,157.1 15.73% -5.80%
2006 6,102.6 14.70% -6.63%
2007 6,202.5 16.58% -5.10%
2008 6,020.7 13.16% -7.89%
2009 5,618.2 5.60% -14.04%

While net emissions were down 14% since 2000, total emissions (i.e. emissions with no adjustments for carbon sinks) were down only 6.75%. I admit I'm not terribly informed in the ways of carbon accounting, but it seems like total or gross emissions are a more direct measure of resource use in the economy. As the table below shows, most of this more modest decline came in 2008 and 2009 while the economy was in recession.

Total Emissions: Sources Alone

Year Total GHG Emissions (Tg) 1 Year Change Total Change Since 1990 Total Change Since 2000
1990 6,182
1991 6,142 -0.65% -0.65%
1992 6,244 1.66% 1.00%
1993 6,367 1.97% 2.99%
1994 6,466 1.55% 4.59%
1995 6,551 1.31% 5.97%
1996 6,767 3.30% 9.46%
1997 6,807 0.59% 10.11%
1998 6,850 0.63% 10.81%
1999 6,916 0.96% 11.87%
2000 7,113 2.85% 15.06%
2001 6,999 -1.60% 13.22% -1.60%
2002 7,039 0.57% 13.86% -1.04%
2003 7,065 0.37% 14.28% -0.67%
2004 7,175 1.56% 16.06% 0.87%
2005 7,214 0.54% 16.69% 1.42%
2006 7,167 -0.65% 15.93% 0.76%
2007 7,263 1.34% 17.49% 2.11%
2008 7,061 -2.78% 14.22% -0.73%
2009 6,633 -6.06% 7.30% -6.75%

And as you can see, in terms of total emissions, 2007 was the most recent peak. So clearly the recession reduced the emissions rate of the US and we can expect it to pick up in 2010 and 2011 as the economy recovered. Still, it's somewhat impressive that while the economy grew 63% (in real terms) since 1990 and the population by almost 23%, emissions have only increased by 7.3%. We're clearly getting better at emissions per GDP and emissions per capita, but we're not yet at the point of unambiguous declines in total emissions.

1. Million metric tons CO2 Equivalent.