The carbon dioxide exchange

One key to accurately predicting future levels of atmospheric carbon dioxide (CO2) is understanding how land and atmosphere exchange CO2. Each year, photosynthesizing land plants remove (fix) one in eight molecules of atmospheric CO2, and respiring land plants and soil organisms return a similar number. This exchange determines whether terrestrial ecosystems are a net carbon sink or source. Two papers in this issue contribute to understanding the land-atmosphere exchange by elegantly analyzing rich data sets on CO2 fluxes from a global network of monitoring sites.