THEGREENGROK    Statistically Speaking

Statistical Grok: U.S. CO2 Emissions by the Numbers

by Bill Chameides | May 30th, 2008
posted by Erica Rowell (Editor)

Permalink | 2 comments


On May 13, 2008 an editorial in the Wall Street Journal (“McCain’s Climate ‘Market’”) argued that there was no critical need for federal climate legislation. Why? Its argument was built around a statistic that net U.S. carbon dioxide (CO2) emissions have fallen by 3% since 2001. Is this true? The correct year is since 2000 not 2001. But even so, the stat and their arguments at best are misleading.

It is true that net CO2 emissions in the United States have dropped since 2000, but you have to be mindful of what we mean by “net emissions.” Scientists distinguish between net emissions and actual emissions. Net emissions are the difference between the actual emissions from burning fossil fuels and the storage of CO2 (for example, from “sinks” like forests and other vegetation). As EPA data in the chart below show, actual emissions of CO2 have not decreased.

Key Stats Between 2000 and 2006

Percent change in U.S. net CO2 emissions: -3%
Percent change in the amount of CO2 U.S. forests and other vegetation absorbed: +31%
Percent change in actual US emissions of CO2: +0.3%

Factors Slowing the Growth in US Emissions: Economy and Weather

The growth in actual emissions since 2000 has been quite small, less than 1%. Does this mean the United States is in the midst of a fundamental change in how energy is produced and used? No, the slow growth is due to a confluence of unrelated events, namely milder weather and a slowed economy.

Years with a decrease in actual US CO2 emissions: 2001 and 2006
Year with the slowest growth in US GDP: 2001
Rate of GDP in 2001: .8%
Year with the lowest need for heating in the U.S. thanks to a warm winter: 2006

Initial Data from 2007

The largest jump in CO2 emissions from U.S. power plants since 1998: +2.9%

CO2 emissions from energy sector: +1.6%


Trends in U.S. Greenhouse Gas Emissions and Sinks in Units of millions of tons of CO2

2000 2001 2002 2003 2004 2005 2006
Actual emissions
(primarily burning fossil fuels)
7,032.6 6,921.3 6,981.2 6,998.2 7,078.0 7,129.9 7,054.2
Sinks (C02 removal and storage in forests and other vegetation 673.6 750.2 826.8 860.9 873.7 878.6 883.7
Net emissions (Actual emissions minus sinks) 6,359.0 6,171.1 6,154.4 6,137.3 6,204.3 6,251.3 6,170.5

Inventory of U.S. Greenhouse Gas Emissions and Sinks (April 2008) USEPA #430-R-08-005.


EPA Trends Report INVENTORY OF U.S. GREENHOUSE GAS EMISSIONS AND SINKS: 1990-2006 (April 2008), USEPA #430-R-08-005
Energy Information Agency –
Bureau of Economic Analysis –
EPA Clean Air Markets –

Energy Information Administration:

filed under: carbon dioxide emissions, faculty, Statistically Speaking


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  1. Patrick McNamara
    Jun 2, 2008

    So how is it the net emissions are calculated then? I’ve always glanced at them in the eia.doe excel files when doing research, but never knew how the “sunk” emissions were deducted.

    • Erica Rowell
      Jun 6, 2008

      Dr. Bill Chameides responds: It is pretty straightforward. You take the total actual emissions (like those from cars and power plants) and subtract the sinks (like uptake of CO2 by forests) to get the net emissions

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