The current imbalance in the global carbon budget (''missing carbon'') is approximately 1.5 to 2.0 PgC/yr. The study by Tans et al. [1990], based on geographically based estimates of industrial emissions, atmospheric data, and a model of atmospheric transport, suggested that the missing carbon was accumulating in terrestrial ecosystems of the northern hemisphere's temperate zone. Two recent analyses of forest growth in this region have reported an accumulation of carbon that approaches 1 PgC/yr, and on the basis of these three studies one might conclude that the carbon budget is close to balanced. These recent analyses are incomplete, however. They included the accumulation of carbon in regrowing forests logged during the last several decades but not the emissions of carbon from plant matrial initially held in those forests before logging. When all of the carbon is accounted for, the net flux of carbon (to forests as well as from forest products and logging debris) is close to zero in these regions. Thus the recent analyses have not uncovered a missing sink for carbon, as claimed. On the contrary, they seem to have confirmed that the current imbalance in the carbon budget cannot be explained by the net accumulation of wood in northern forests. If the entire global imbalance is accumulating in the biomass of these forests, the required accumulation rate is too large to have been missed by forest surveys. An annual flux of 1.5 to 2.0 PgC/yr seems too large to be accommodated in aboveground vegetation anywhere. ¿ American Geophysical Union 1993 |