Improving Model Representation of CO2 Effects


AgMIP Crop modelers and FACE scientists improve CO2 effect representation after collaborative workshop

By Delphine Deryng and Greg Reppucci

An international group of AgMIP crop modelers and Free-Air Concentration Enrichment (FACE) scientists recently convened to examine the methodologies for improving model representation of CO2 effects on crop photosynthesis and water use.

Pipes surrounding a soybean plot

CO2 is released through the tiny holes

Heaters in a soybean plot, designed to examine the interaction between CO2 and heat-stress

The workshop, co-organized by Dr. Thomas Pugh (University of Birmingham), Dr. Delphine Deryng (Climate Analytics and Columbia University) and Dr. Andrew Leakey (University of Illinois), was supported by a seed grant from the Birmingham-Illinois Partnership for Discovery, Engagement and Education (BRIDGE) and was held near the Soybean Free Air Concentration Enrichment (SoyFACE) experimental site at the University of Illinois in Urbana-Champaign (IL) from 16-18 August 2017.

This model improvement workshop originated from work led by AgMIP researcher and Climate Analytics scientific advisor Dr. Delphine Deryng. In a paper published in the journal Nature Climate Change (doi:10.1038/nclimate2995), Deryng highlighted the limitation of global crop modeling tools in representing effects of elevated [CO2] on crop yield and crop water use. “CO2 appeared to make up for a large part of the simulated uncertainty”, said Deryng, “and model improvement in respect to CO2 has been very limited over the past 30 years despite significant progress on the experimental side.”

During the workshop, AgMIP and FACE scientists exchanged recent research with one another. To better comprehend crop model capabilities, model methods were presented to FACE scientists. In turn, FACE scientists presented crop modelers with results from recent experiments on several crop-CO2 processes, including biomass production and partitioning, water use, scaling from leaf to canopy, and interactions with temperature, water and nutrients stresses. This exchange encouraged productive discussion, improving model equations to better quantify CO2 processes and designing future FACE experiments that will meet the need of crop modelers.

Overall, improvements in CO2 representation in modelling scenarios were made. These improvements will assist in reducing uncertainty currently found in model simulations. Additionally, the co-design of future research experiments will further help in improving model capabilities going forward.

The collaboration with SoyFACE scientist, Dr. Andrew Leakey, started at the Adaptation Future conference in Rotterdam (May 2016), during which Deryng organized a session to discuss the role of CO2 in adapting cropping systems under climate change. During the summer of 2016, while Deryng visited Leakey and colleagues Dr. Elisabeth Ainsworth and Dr. Carl Bernacchi at the University of Illinois at Urbana -Champaign, the workshop was developed and planned for the subsequent year.

Deryng et al. (2016). Regional disparities in the beneficial effects of rising CO2 concentrations on crop water productivity. NCC. 6, 786–790. doi:10.1038/nclimate2995