A roadmap for improving the representation of photosynthesis in Earth system models

Abstract

Summary Accurate representation of photosynthesis in terrestrial biosphere models ( TBM s) is essential for robust projections of global change. However, current representations vary markedly between TBM s, contributing uncertainty to projections of global carbon fluxes. Here we compared the representation of photosynthesis in seven TBM s by examining leaf and canopy level responses of photosynthetic CO 2 assimilation ( A ) to key environmental variables: light, temperature, CO 2 concentration, vapor pressure deficit and soil water content. We identified research areas where limited process knowledge prevents inclusion of physiological phenomena in current TBM s and research areas where data are urgently needed for model parameterization or evaluation. We provide a roadmap for new science needed to improve the representation of photosynthesis in the next generation of terrestrial biosphere and Earth system models.