UC San Diego

We explore the ability of the atmospheric CO₂ record since 1900 to constrain the source of CO₂ from land use and land cover change (hereafter "land use"), taking account of uncertainties in other terms in the global carbon budget. We find that the atmospheric constraint favors land use CO₂ flux estimates with lower decadal variability and can identify potentially erroneous features, such as emission peaks around 1960 and after 2000, in some published estimates. Furthermore, we resolve an offset in the global carbon budget that is most plausibly attributed to the land use flux. This correction shifts the mean land use flux since 1900 across 20 published estimates down by 0.35 PgC year^-1 to 1.04 ± 0.57 PgC year^-1 , which is within the range but at the low end of these estimates. We show that the atmospheric CO₂ record can provide insights into the time history of the land use flux that may reduce uncertainty in this term and improve current understanding and projections of the global carbon cycle.