Terrestrial biosphere model performance for inter-annual variability of land-atmosphere CO 2 exchange

T. F. Keenan, Ian Baker, Alan Barr, Philippe Ciais, Ken Davis, Michael Dietze, Danillo Dragoni, Christopher M. Gough, Robert Grant, David Hollinger, Koen Hufkens, Ben Poulter, Harry Mccaughey, Brett Raczka, Youngryel Ryu, Kevin Schaefer, Hanqin Tian, Hans Verbeeck, Maosheng Zhao, Andrew D. Richardson

Research output: Contribution to journalArticlepeer-review

221 Scopus citations


Interannual variability in biosphere-atmosphere exchange of CO 2 is driven by a diverse range of biotic and abiotic factors. Replicating this variability thus represents the 'acid test' for terrestrial biosphere models. Although such models are commonly used to project responses to both normal and anomalous variability in climate, they are rarely tested explicitly against inter-annual variability in observations. Herein, using standardized data from the North American Carbon Program, we assess the performance of 16 terrestrial biosphere models and 3 remote sensing products against long-term measurements of biosphere-atmosphere CO 2 exchange made with eddy-covariance flux towers at 11 forested sites in North America. Instead of focusing on model-data agreement we take a systematic, variability-oriented approach and show that although the models tend to reproduce the mean magnitude of the observed annual flux variability, they fail to reproduce the timing. Large biases in modeled annual means are evident for all models. Observed interannual variability is found to commonly be on the order of magnitude of the mean fluxes. None of the models consistently reproduce observed interannual variability within measurement uncertainty. Underrepresentation of variability in spring phenology, soil thaw and snowpack melting, and difficulties in reproducing the lagged response to extreme climatic events are identified as systematic errors, common to all models included in this study.

Original languageEnglish (US)
Pages (from-to)1971-1987
Number of pages17
JournalGlobal change biology
Issue number6
StatePublished - Jun 2012
Externally publishedYes


  • Biosphere-atmosphere interaction
  • Carbon fluxes
  • Carbon sequestration
  • Interannual variability
  • Process-based models
  • Remote sensing

ASJC Scopus subject areas

  • Global and Planetary Change
  • Environmental Chemistry
  • Ecology
  • General Environmental Science


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