Effects of model structural uncertainty on carbon cycle projections: Biological nitrogen fixation as a case study

William R. Wieder, Cory C. Cleveland, David M. Lawrence, Gordon B. Bonan

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Uncertainties in terrestrial carbon (C) cycle projections increase uncertainty of potential climate feedbacks. Efforts to improve model performance often include increased representation of biogeochemical processes, such as coupled carbon-nitrogen (N) cycles. In doing so, models are becoming more complex, generating structural uncertainties in model form that reflect incomplete knowledge of how to represent underlying processes. Here, we explore structural uncertainties associated with biological nitrogen fixation (BNF) and quantify their effects on C cycle projections. We find that alternative plausible structures to represent BNF result in nearly equivalent terrestrial C fluxes and pools through the twentieth century, but the strength of the terrestrial C sink varies by nearly a third (50 Pg C) by the end of the twenty-first century under a business-as-usual climate change scenario representative concentration pathway 8.5. These results indicate that actual uncertainty in future C cycle projections may be larger than previously estimated, and this uncertainty will limit C cycle projections until model structures can be evaluated and refined.

    Original languageEnglish
    Article number044016
    JournalEnvironmental Research Letters
    Volume10
    Issue number4
    DOIs
    StatePublished - Apr 1 2015

    Keywords

    • biological nitrogen fixation
    • carbon cycle
    • climate change
    • community land model
    • Earth system modeling
    • structural uncertainty

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