(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: The United States absorbs more CO2 into its land than it emits into the air. The world should be grateful.

Answer: As often the case, at the heart of this talking point is a grain of truth. But it does not serve the purpose for which it’s been enlisted. According to the U.S. Department of Energy land-use changes in the U.S. between 1952 and 1992 have resulted in a net absorption of CO2. But this is only true of natural CO2 — the natural flux of CO2 into and out of forests and peat bogs and soil, as well as carbon that’s been sequestered as lumber and other wood products. These fluxes are actually much larger than anthropogenic emissions, but they go both ways, whereas fossil fuel burning only emits carbon.

This net sink of natural carbon has only been sufficient to offset around 25% of fossil fuel carbon emissions from vehicles, power plants, and the like. In Chapter 7 of this 1996 report, the DoE notes:

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For purposes of comparison, this estimated amount of sequestered carbon offset approximately 17 percent of the 1,381 million metric tons of carbon (or 5,068 million metric tons of carbon dioxide) emitted in the United States in 1992 from the burning of fossil fuels.

So at least for 1992, that leaves 83% of fossil-fuel emissions in the atmosphere to spread over the globe or be absorbed into the oceans. In the 2003 report, that number has increased to 83.1%:

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The U.S. Environmental Protection Agency (EPA) estimates annual U.S. carbon sequestration in 2003, based on data generated by the U.S. Department of agriculture (USDA), at 828.0 million metric tons carbon dioxide equivalent (MMTCO2e), a decline of approximately 21 percent from the 1,042.1 MMTCO2e sequestered in 1990 (Table 33). Land use, land-use change, and forestry practices offset approximately 16.9 percent of total U.S. anthropogenic carbon dioxide emissions in 1990 and 11.9 percent in 2003. [page 75-76]

With per capita emissions five times greater than the global average, that leaves a lot the world does not have to thank the U.S. for.