Analyzing Carbon Flux Measurements

摘要

We read with considerable interest Christian Koerner's analysis and criticism of carbon flux measurements in Kyoto protocol accounting ("Slow in, rapid out―carbon flux studies and Kyoto targets," Perspectives, 23 May, p. 1242). Although we agree with his analysis of the carbon cycle in slow and fast processes, it appears to us that there is a misunderstanding about the use of the eddy-covariance measurements in current efforts to determine the carbon balance of continents or large geographical regions. In the United States and Europe (1), the flux measurements form an integral part of the experimental program that is based around the multiple constraint approach to close the carbon balance. The key rationale behind these efforts is that, ultimately, fluxes from the land, both the slow and the fast ones, affect atmospheric concentrations of CO_2 at a regional scale and that the slow and fast fluxes ideally should match. The multiple constraint approach uses this concept to predict carbon fluxes on all scales. Two major continental-scale programs, the U.S.