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Interstate Differences in Greenhouse Gas Emissions: Much Less Than Meets the Eye

Laurie Johnson

Posted June 18, 2009 in Solving Global Warming

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U.S. per capita greenhouse emissions show tremendous differences between states, prompting concern that some states would bear much heavier burdens from a cap on global warming emissions than others. For example, while national per capita emissions are 20.6 metric tons CO2 (mT CO2), Washington D.C. averages less than 7 mT CO2, while Wyoming is over 128 mT CO2, a more than 18 fold difference.[1]

The differential impacts citizens would experience between states, however, is much lower than these simple averages suggest. Two factors have to be taken into consideration. First, some states, such as Wyoming, do not actually consume all of the electricity they produce-some of the carbon price attached to Wyoming's emissions will be felt by citizens in other states consuming Wyoming's electricity generation. Similarly, any price increases resulting from caps on industrial emissions will be felt nationwide by consumers of the products associated with those emissions.

This brief entry demonstrates the effect these two factors have on differences between state emission levels, showing that once they are taken into account, disparities are much smaller than first meets the eye.

Interstate electricity sales

A substantial amount of electricity production crosses state lines: some states export electricity generation they don't use, while others import it. To assess impacts on a state's citizens resulting from a cap on carbon, emissions must therefore be adjusted to reflect where they are consumed and paid for, not where they are generated.

Figures 1a and 1b compare per capita emissions based upon where electricity is generated versus where it is used.[2]

Emissions Generation Basis

Emissions Use Basis

Source: Greenhouse Gases and the American Lifestyle: Understanding the Interstate Differences in Emissions, Ackerman, F., Sheeran, K., and Stanton, E. April 2009.

 

Without any adjustment for interstate electricity transmissions, the per capita average emissions of the top 5 emitting states, Wyoming, North Dakota, Alaska, West Virginia, and Louisiana, is 7.6 times higher than that of the 5 lowest emitting states, Washington D.C, Rhode Island, Vermont, California, and New York. After accounting for interstate electricity sales, the ratio drops down to 4.4, and the ordering changes somewhat. As would be expected, emissions from Wyoming, West Virginia, and North Dakota, which account for 26 percent of all electricity sales crossing state lines, are significantly affected by this adjustment.

Industrial emissions

In addition to adjusting for interstate electricity sales, a second adjustment is needed to exclude industrial emissions. Emissions from industrial production help create goods that are sold around the entire country, or even outside the United States altogether. The majority of carbon costs will be passed on to the final consumers and will therefore be felt outside the state in which the associated goods are produced. For this reason, industrial emissions that vary by state do not imply any specific burden per se to the state in which they occur.[3]

Figures 2a and 2b show per capita emissions with and without including the industrial sector. The change further brings down the ratio of the top 5 to the bottom 5 from 4.4 to 2.8.

Emissions with industrial

Emissions without Industrial

Source: Greenhouse Gases and the American Lifestyle: Understanding the Interstate Differences in Emissions, Ackerman, F., Sheeran, K., and Stanton, E. April 2009.

Conclusion

Interstate emissions appear to vary sharply when comparing them based upon a state's generation mix of electricity. Upon closer examination, however, differences are much smaller than one would expect, due to interstate consumption of electricity, and the fact that consumption of industrial products occurs nationwide, rather than the state in which they are produced (and in which the emissions occur). Once emissions are adjusted for these factors, state differences are a small fraction of total emissions (Figure 1a versus Figure 2b).

 


 

[1] All calculations in this brief are based upon 2004 data, the year in which sources for all data were available. More recent numbers will have similar proportions between states, and therefore would provide similar results to those presented here.

[2] The methodology used to adjust for interstate electricity sales can be found in Appendix D, of Greenhouse Gases and the American Lifestyle, by Ackerman, F., Sheeran, K., and Stanton, E.A., April 2009.

[3] While consumers are impacted across the nation, workers in these industries are specific to where the production takes place. The Waxman-Markey bill, however, includes a provision to dedicate up to 15% of allowances to energy-intensive manufacturers selling in competitive international markets on an output basis. EPA's analysis of the Waxman-Markey bill shows that this allocation prevents job losses from the bill in these industries (http://www.epa.gov/climatechange/economics/economicanalyses.html#wax).

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Switchboard is the staff blog of the Natural Resources Defense Council, the nation’s most effective environmental group. For more about our work, including in-depth policy documents, action alerts and ways you can contribute, visit NRDC.org.

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