Chapter 2, Key Finding 4
Using bottom-up, inventory-based calculations, the Second State of the Carbon Cycle Report (SOCCR2) estimates that the average annual strength of the land-based carbon sink in North America was 606 Tg C per year (±75%) during the 2004 to 2013 time period, compared with the estimated 505 Tg C per year (±50%) in ca. 2003, as reported in the First State of the Carbon Cycle Report (CCSP 2007). There is apparent consistency in the two estimates, given their ranges of uncertainty, with SOCCR2 calculations including additional information on the continental carbon budget. However, large uncertainties remain in some components (very high confidence).