Chapter 8, Key Finding 2
Inverse model analyses of atmospheric CO2 data suggest substantial interannual variability in net carbon uptake over North America. Over the period 2004 to 2013, North American fossil fuel emissions from inventories average 1,774 ± 24 teragrams of carbon (Tg C) per year, partially offset by the land carbon sink of 699 ± 82 Tg C per year. Additionally, inversion models suggest a trend toward an increasing sink during the period 2004 to 2013. These results contrast with the U.S. land sink estimates reported to the United Nations Framework Convention on Climate Change, which are smaller and show very little trend or interannual variability.