Identification and characterization of abrupt changes in the land uptake of carbon

Claudie Beaulieu, Jorge L. Sarmiento, Sara E. Mikaloff Fletcher, Jie Chen, David Medvigy

Research output: Contribution to journalArticle

20 Scopus citations


A recent study of the net land carbon sink estimated using the Mauna Loa, Hawaii atmospheric CO 2 record, fossil fuel estimates, and a suite of ocean models suggests that the mean of the net land carbon uptake remained approximately constant for three decades and increased after 1988/1989. Due to the large variability in the net land uptake, it is not possible to determine the exact timing and nature of the increase robustly by visual inspection. Here, we develop a general methodology to objectively determine the nature and timing of the shift in the net land uptake based on the Schwarz Information Criterion. We confirm that it is likely that an abrupt shift in the mean net land carbon uptake occurred in 1988. After taking into account the variability in the net land uptake due to the influence of volcanic aerosols and the El Nio Southern Oscillation, we find that it is most likely that there is a remaining step increase at the same time (p-values of 0.01 and 0.04 for Mauna Loa and South Pole, respectively) of about 1 Pg C/yr. Thus, we conclude that neither the effect of volcanic eruptions nor the El Nio Southern Oscillation are the causes of the sudden increase of the land carbon sink. By also applying our methodology to the atmospheric growth rate of CO 2, we demonstrate that it is likely that the atmospheric growth rate of CO 2 exhibits a step decrease between two fitted lines in 1988-1989, which is most likely due to the shift in the net land uptake of carbon.

Original languageEnglish (US)
Article numberGB1007
JournalGlobal Biogeochemical Cycles
Issue number1
Publication statusPublished - Jan 30 2012
Externally publishedYes


ASJC Scopus subject areas

  • Global and Planetary Change
  • Environmental Chemistry
  • Environmental Science(all)
  • Atmospheric Science

Cite this