Submitted as: review and perspective paper 25 May 2021

Submitted as: review and perspective paper | 25 May 2021

Review status: this preprint is currently under review for the journal GMD.

Validation of Terrestrial Biogeochemistry in CMIP6 Earth System Models: A Review

Lynsay Spafford1,2 and Andrew Hugh MacDougall1 Lynsay Spafford and Andrew Hugh MacDougall
  • 1Climate and Environment, Saint Francis Xavier University, Antigonish, Canada
  • 2Environmental Sciences, Memorial University, St. John’s, Canada

Abstract. The vital role of terrestrial biogeochemical cycles in influencing global climate change is explored by modelling groups internationally through Land Surface Models (LSMs) coupled to atmospheric and oceanic components within Earth System Models (ESMs). The sixth phase of the Coupled Model Intercomparison Project (CMIP6) provided an opportunity to compare ESM output by providing common forcings and experimental protocols. Despite these common experimental protocols, a variety of terrestrial biogeochemical cycle validation approaches were adopted by CMIP6 participants, leading to ambiguous model performance assessment and uncertainty attribution across ESMs. In this review we summarize current methods of terrestrial biogeochemical cycle validation utilized by CMIP6 participants and concurrent community model comparison studies. We focus on variables including: the dimensions of evaluations, observation-based reference datasets, and metrics of model performance. To ensure objective and thorough validations for the seventh phase of CMIP (CMIP7) we recommend the use of a standard validation protocol employing a broad suite of certainty-weighted observation-based reference datasets, targeted model performance metrics, and comparisons across a range of spatiotemporal scales.

Lynsay Spafford and Andrew Hugh MacDougall

Status: open (until 20 Jul 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Lynsay Spafford and Andrew Hugh MacDougall

Lynsay Spafford and Andrew Hugh MacDougall


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Short summary
Land biogeochemical cycles influence global climate change. Their influence is examined through complex computer models which account for the interaction of the land, ocean, and atmosphere. Improved models used in the recent round of model intercomparison used inconsistent validation methods to compare simulated land biogeochemistry to datasets. For the next round of model intercomparison we recommend a validation protocol with explicit reference datasets and informative performance metrics.