Rosenzweig, et al., 2013

By Greg Reppucci

The Global Gridded Crop Model Intercomparison (GGCMI) team has just released Phase 2 Protocols for the Carbon, Temperature, Water, Nitrogen and Adaptation (CTWN-A) sensitivity study. The simulation experiment officially starts now! First deadlines for data submissions are March 2016.

The focus of GGCMI is to bring together and sustain an international and diverse community of crop modelers to assess climate impacts at continental and global scales and compare and improve models. Input data and model results are assimilated and shared through a robust IT infrastructure based on Globus technology and allows for real time collaboration among spatially separated modeling groups. Data processing and analysis is conducted through a pipeline of software tools managed in an open-source code repository. Over 20 modeling groups from over 10 countries currently participate in the GGCMI.

During Phase 1 of the GGCMI, crop modelers, given similar input data and procedures, ran and compared historical simulations to historical observations in an effort to establish the commonalities and differences of crop models. Phase 2 enhances this with a large ensemble to evaluate sensitivity across CTWN-A.

The protocols establish a common procedure among crop modelers. Participating modeling groups follow the outlined framework, allowing for a cohesive and consistent comparison of resulting model outputs.

The primary outcomes of the project so far include a detailed comparison of the major differences and similarities among global gridded crop models, evaluation of model and ensemble hindcasting skill, quantification of key uncertainties from climate input data, model choice, and other sources, and multi-model analysis of the agricultural impacts of large-scale climate extremes from the historical record. Expected outcomes from Phase 2 include detailed assessments of large-scale model response, next-generation multi-model climate impact emulators for use in downstream analysis and economic or integrated assessment models, and a first-of-its-kind analysis of model response at daily time-scales spanning the whole globe.

The AgMIP community is open to expanding the GGCMI network to any interested modeling groups. Gridded crop modelers, who are not already involved but wish to participate in the very exciting Phase 2, please contact Joshua Elliott and Christoph Müller at

Click here for the full GGCMI protocols.
Published open-source Phase 1 protocols can be found here.
Open-source pipeline for Phase 1 can be found here.