Climatic Change

, Volume 33, Issue 1, pp 31–62

Accounting for the missing carbon-sink with the CO2-fertilization effect


  • Haroon S. Kheshgi
    • Corporate Research Laboratories, Exxon Research and Engineering Company
  • Atul K. Jain
    • Department of Atmospheric SciencesUniversity of Illinois
  • Donald J. Wuebbles
    • Department of Atmospheric SciencesUniversity of Illinois

DOI: 10.1007/BF00140512

Cite this article as:
Kheshgi, H.S., Jain, A.K. & Wuebbles, D.J. Climatic Change (1996) 33: 31. doi:10.1007/BF00140512


A terrestrial-biosphere carbon-sink has been included in global carbon-cycle models in order to reproduce past atmospheric CO2, 13C and 14C concentrations. The sink is of large enough magnitude that its effect on projections of future CO2 levels should not be ignored. However, the cause and mechanism of this sink are not well understood, contributing to uncertainty of projections. The estimated magnitude of the biospheric sink is examined with the aid of a global carbon-cycle model. For CO2 emissions scenarios, model estimates are made of the resulting atmospheric CO2 concentration. Next, the response of this model to CO2-emission impulses is broken down to give the fractions of the impulse which reside in the atmosphere, oceans, and terrestrial biosphere - all as a perturbation to background atmospheric CO2 concentration time-profiles that correspond to different emission scenarios. For a biospheric sink driven by the CO2-fertilization effect, we find that the biospheric fraction reaches a maximum of roughly 30% about 50 years after the impulse, which is of the same size as the oceanic fraction at that time. The dependence of these results on emission scenario and the year of the impulse are reported.

Copyright information

© Kluwer Academic Publishers 1996