Results from recent models in the coupled carbon cycle
climate model intercomparison project (C4MIP) indicate a positive feedback to
global warming from the interactive carbon cycle, but the magnitude varies
widely. A typical model simulates an additional increase of 90 ppmv in the
atmospheric CO2, and 0.6 degree additional warming due to this
feedback, but some model can be as large as 250ppm. Using a liner perturbation
framework, we analyze what might have caused such large discrepancy in the
models, with a focus on land where the largest uncertainties lie. Change in NPP
such as different sensitivity to the CO2 fertilization effect is one
where in some models it is modest largely due to the multiple limiting factors
constraining terrestrial productivity and carbon loss. The large differences
among the models are also manifestations of other poorly constrained processes
such as the turnover time and rates of soil decomposition.
Author: N. Zeng, H. Qian, E. Munoz and R. Iacono
Filesize: 11.58 Kb