Can climate variability contribute to the "missing" CO2 sink?

Dai, A.  and  I.Y. Fung

Global Biogeochem. Cycles, 7,   599-609.


The contemporary carbon budget for the atmosphere requires a large "missing" carbon
sink to balance anthropogenic carbon inputs. We investigated climatic effects on carbon exchanges between the atmosphere and the undisturbed biosphere and assessed the possible contribution of climate variability to the carbon sink. Empirical models and global temperature and precipitation data sets were used in the study. It was found that climate
perturbations during 1940-1988 caused considerable variations in plant productivity and
soil respiration. The different sensitivities of the fluxes to climate perturbations led to a significant carbon accumulation in the biosphere. The cumulative carbon sink for the
period 1950-1984 (~20±5 GtC or 10**12 kg C) was predominantly located in mid-latitudes
in the northern hemisphere (30-60°N) and could amount to half of the missing CO2 sink as derived from deconvolution analyses. Our results indicate that climate variations have unequal impacts on biospheric carbon fluxes from different ecosystems and imply that caution must be exercised in generalizing in situ observations to the globe.