Two years ago, researchers at Purdue University working in conjunction with NASA Project Vulcan released preliminary estimates of the carbon dioxide emissions by all counties in the 50 United States (see Purdue press release, ENN article).

Preliminary data suggested that Houston’s Harris County emitted the most carbon dioxide in the USA. Since then, the same research team has fine-tuned its analysis and reduced various sources of error, leading to a final set of findings released at the beginning of this year to little publicity and no fanfare. The new findings place Los Angeles County on top of the CO2 rankings for releasing a whopping 21.5 million tons of carbon dioxide into the atmosphere in one year.

Here is the final Purdue/NASA ranking of the top 20 counties in CO2 emissions, measured in units of millions of tons:

1. Los Angeles County, CA: 21.5 million tons in a year
2. Harris County, TX (Houston): 19.6
3. Cook County, IL (Chicago): 16.5
4. Cuyahoga County, OH (Cleveland): 12.1
5. Wayne County, MI (Detroit): 8.9
6. Hennepin County, MN (Minneapolis): 8.6
7. Wilcox County, AL (Camden): 8.5
8. San Juan County, NM (Farmington): 8.5
9. East Baton Rouge, LA: 7.6
10. San Diego County, CA: 7.5
11. Maricopa County, AZ (Phoenix): 7.4
12. Jefferson County, AL (Birmingham): 7.4
13. Carbon County, PA (Jim Thorpe): 7.4
14. Titus County, TX (Mt. Pleasant): 7.3
15. Clark County, NV (Las Vegas): 6.8
16. Porter County, IN (Valparaiso): 6.6
17. Dallas County, TX: 6.3
18. Hillsborough County, FL (Tampa): 6.3
19. Jefferson County, OH (Steubenville): 6.3
20. Indiana County, PA (Indiana): 6.3

To get a general idea of the patterns of CO2 emissions across the United States, see the map below, plotted in cells as small as six miles across:

Hello, New Jersey. Some of the patterns in CO2 emissions are evident in this map: CO2 emissions are greatest where the most people live and where the most people drive — you could plan a cross-country highway trip using that map. While it’s true that Los Angeles, Houston and Chicago are the biggest emitters of CO2, it’s also true that the most people live there. It might not be fair to see that ranking as an indication of environmental sin. To filter out the effect of population size, let’s look at the 20 counties in the USA that emit the greatest number of tons of CO2 per person who lives there. It’s a very different list:

1. Oliver County, North Dakota (Center): 800.3 tons/person in a year
2. Mercer County, North Dakota (Stanton): 674.3
3. Wilcox County, Alabama (Camden): 654.8
4. Rosebud County, Montana (Forsyth): 454.1
5. Platte County, WY (Wheatland): 410.0
6. North Slope Borough, AK (Barrow): 385.2
7. Emery County, UT (Huntington): 381.6
8. Stewart County, TN (Clarksville): 374.5
9. Pleasants County, WV (St. Marys): 315.5
10. Millard County, UT (Delta): 312.2
11. Carroll County, KY (Carrollton): 309.1
12. McLean County, ND (Washburn): 299.1
13. Pike County, IN (Petersburg): 295.3
14. Linn County, KS (Pleasanton): 294.0
15. Grant County, WV (Petersburg): 293.6
16. Heard County, GA (Franklin): 278.1
17. Titus County, TX (Mt. Pleasant): 258.4
18. Pottawatomie County, KS (Westmoreland): 256.6
19. Monroe County, GA (Forsyth): 247.4
20. Spencer County, IN (Rockport): 211.4

There’s a steep drop-off within the top 20 CO2 producers per capita, but each of the top 20 counties is extraordinary: among counties in the USA, the median CO2 per person produced is 4.1 tons in a year, much lower than in these counties. What do you think is going on in these places to raise the per capita CO2 production so high? The Purdue University climate team has data to give us an answer. 14 of the top 20 emitting counties per capita are home to one of top 50 CO2 emitting power plants in the nation. Another 4 of the top 20 are home to one of the top 100 CO2 emitting power plants. Wilcox County gets its status for a high-emissions paper plant, and the North Slope of Alaska is famous for its oil production.

The important roles played by people, transportation and power production in producing carbon dioxide emissions in the United States is clarified by looking at Purdue/NASA data on the sources of CO2 in the United States overall:

Commercial, industrial and power-related production of CO2 can be addressed through changes in policy by government bodies, policy changes for which people can advocate through social movement and election activity. Transportation and residential emission of CO2 is accomplished personally by you and me and can be addressed personally. According to Purdue/ NASA Project Vulcan statistics, there isn’t much variability from county to county in transportation and residential emissions. This indicates that while individual people may be able to make some changes to reduce their household and car carbon dioxide production, they’re changes we need to make in all areas of the nation.

A postscript: this data is taken from observations made in the year 2002, and it’s the last year for which such data is available. Why no updated information? NASA’s Orbiting Carbon Observatory was meant to leapfrog over this data with constant satellite measurements of CO2 production in various geographic areas. Sadly, it crashed into the ocean after its launch in 2009, and a significant opportunity to expand our understanding of CO2 production by people was lost.