The United States' role in climate disruption is far greater than most people realize. Not only does the U.S. emit more carbon dioxide (CO2) than any other nation besides China, not only does the U.S. have one of the highest per-capita emissions levels in the world, but the U.S. economy also accounts for a massive amount of emissions released by the rest of the world.
I crunched the numbers to see just how much CO2 the United States economy is actually responsible for. The results are disturbing.
Every product and service requires energy, and thus carbon. Commercial agriculture requires petroleum or natural gas-based fertilizers and diesel fuel for planting and harvesting. Manufacturing requires energy to extract raw materials, petroleum to transport those materials to a factory, energy to convert those materials into products, and yet more petroleum to transport the products to end users. Even services like housecleaning or web site hosting have an energy cost, the former in the creation of chemicals and electric cleaning tools and the latter for the server (a product with its associated energy cost of creation), the electricity used to run the computer, and the energy consumed in constructing the computer center that houses the server. And in all cases, the energy cost to create the product or service creates carbon emissions.
Given this, the amount of CO2 that a product or service indirectly emits in its creation, transport and use can be estimated. And by extension, the total amount of CO2 produced by the combined products and services (gross domestic product) of a nation can be estimated. The total CO2 emissions from consumption of energy per dollar of a country's GDP is called carbon intensity.
The official carbon intensity of the United States in 2006, as noted by the Department of Energy, was 0.52 metric tons of CO2 emitted per thousand dollars (indexed for inflation to the value of the dollar in 2000). For comparison, the carbon intensity of Iceland in 2006 was 0.31 metric tons of CO2 per thousand dollars, and the carbon intensity of Russia was 4.54 metric tons of CO2 per thousand dollars.
The fact that carbon intensity varies from country to country is a function of the country's energy mix and overall productivity -- more coal or oil burned for electricity or heating produces higher carbon intensity, and lots of manual labor producing valuable products produces a higher carbon intensity, too. Large amounts of manual labor producing inexpensive products produces an extremely low carbon intensity, as witnessed by the very low carbon intensity of 0.10 metric tons of CO2 emitted per thousand dollars from Cambodia.
From carbon intensity, we can estimate the amount of CO2 produced in the process of creating the goods and services that the U.S. exports -- and that other countries export to us. The result is the following graph:
Figure 1 shows the 15 nations that "export" the most CO2 to the United States in goods and services used in the U.S. economy. In essence, anything the U.S buys that says "Made in China" is part of the U.S. economy, so the carbon emitted in the creation of that product belongs to the U.S. economy as much as the carbon emitted in manufacturing a Ford Focus in Detroit does. Figure 1 represents the balance of carbon, imported CO2 from other nations to the U.S. minus the CO2 the U.S. exports to them, as determined from the nations' carbon intensity. It's clear that China contributes by far the most CO2 to U.S. carbon emissions.
In words, the graph says that the U.S. exported over a billion metric tons of CO2 to the rest of the world in 2006.
Figure 2 below illustrates data in a similar fashion, but as a percentage of total U.S. carbon emissions:
In this case, U.S.-generated emissions as a percentage of total emissions attributable to the U.S. economy have fallen steadily since 1985, from a high of 97.8% to 79.3%. That means the U.S. economy has offshored 20.7% of our CO2emissions the same way it has offshored production and jobs.
If the U.S. is no longer generating a significant amount of our CO2 emissions, that means the official carbon intensity of the United States (0.52 metric tons per thousand dollars) is actually much higher. And if that is the case, then the reduction in carbon intensity that many people are pleased about is at least partly an illusion. Figure 3 below illustrates how much an illusion the regular improvements in U.S. carbon intensity actually is:
Figure 3 reveals an unpleasant fact -- as U.S. businesses have offshored more and more of the U.S. economy's CO2 emissions to parts of the world where the carbon intensity is higher but labor is cheaper, the economy's real carbon intensity has actually worsened since hitting its all-time low in 2001.
These figures illustrate a vitally important conclusion -- the U.S. economy demands a huge amount of CO2emissions beyond its borders. The U.S. has essentially offshored its greenhouse gas emission problem to the rest of the world, turning their economies into dumping grounds for our own air pollution. Yes, they've been paid well for it in U.S. dollars that helped raise the standard of living in affected countries. But this also means the U.S. has a responsibility to help those countries clean their dirty energy houses.
After all, wouldn't you want your neighbor to rake up all the leaves he blew into your yard?
I acquired the US GDP data, carbon intensity data related to energy production and gas flaring, and U.S. imports and exports from the data repositories listed below in sources and then performed the calculations that resulted in the graphs above. The Excel file of these calculations is available here (zipped Excel file) for anyone wishing to verify the calculations.
The EIA data on carbon intensity is only from the consumption of fossil fuels and flaring of gas -- it does not include agricultural emissions, for example. In addition, the calculations are for carbon dioxide alone, excluding methane, ozone and other long lived greenhouse gases.
This analysis assumes that all units of production for import and export are equivalent in terms of CO2 emissions, while this is certainly untrue. However, given the large variety of imports and exports, and thus a large variety of CO2 emission profiles, I believe this assumption is reasonable.
The estimates of imported (and exported) CO2 are equal the carbon intensity multiplied by the value of the imports, with the net amount of CO2 generated by other nations on behalf of the U.S. defined as the CO2 imports minus the exports.
Finally, all nations have data from 1992 until 2006, but only major trading partners have data from 1985 until 2006. This produces an error in the data from 1985 to 1992. Given that over 90% of all emissions are via major trading partners such as China and Canada, this error is believed to be relatively small.
US GDP information (Excel file)
Energy related carbon intensity (Excel file)