Abstract
Abstract. Concerns about food security under climate change motivate efforts to better understand future changes in crop yields. Process-based crop models, which represent plant physiological and soil processes, are necessary tools for this purpose since they allow representing future climate and management conditions not sampled in the historical record and new locations to which cultivation may shift. However, process-based crop models differ in many critical details, and their responses to different interacting factors remain only poorly understood. The Global Gridded Crop Model Intercomparison (GGCMI) Phase 2 experiment, an activity of the Agricultural Model Intercomparison and Improvement Project (AgMIP), is designed to provide a systematic parameter sweep focused on climate change factors and their interaction with overall soil fertility, to allow both evaluating model behavior and emulating model responses in impact assessment tools. In this paper we describe the GGCMI Phase 2 experimental protocol and its simulation data archive. A total of 12 crop models simulate five crops with systematic uniform perturbations of historical climate, varying CO2, temperature, water supply, and applied nitrogen (“CTWN”) for rainfed and irrigated agriculture, and a second set of simulations represents a type of adaptation by allowing the adjustment of growing season length. We present some crop yield results to illustrate general characteristics of the simulations and potential uses of the GGCMI Phase 2 archive. For example, in cases without adaptation, modeled yields show robust decreases to warmer temperatures in almost all regions, with a nonlinear dependence that means yields in warmer baseline locations have greater temperature sensitivity. Inter-model uncertainty is qualitatively similar across all the four input dimensions but is largest in high-latitude regions where crops may be grown in the future.
Highlights
Understanding crop yield response to a changing climate is critically important, especially as the global food production system will face pressure from increased demand over the century (Foley et al, 2005; Bodirsky et al, 2015)
The 12 models included in Global Gridded Crop Model Intercomparison (GGCMI) Phase 2 are all processbased crop models that are widely used in impacts assessments (Table 3)
The GGCMI Phase 2 protocol includes a second set of experiments, “A1”, that assume that future cultivars are modified to adjust to changes along the T dimension in the CTWN experiment
Summary
Understanding crop yield response to a changing climate is critically important, especially as the global food production system will face pressure from increased demand over the century (Foley et al, 2005; Bodirsky et al, 2015). Process-based models have been widely used in studies on future food security (Wheeler and Von Braun, 2013; Elliott et al, 2014a; Frieler et al, 2017), options for climate mitigation (Müller et al, 2015) and adaptation (Challinor et al, 2018), and future sustainable development (Humpenöder et al, 2018; Jägermeyr et al, 2017) They are a necessity for global gridded simulations, which allow understanding the global dynamics of agricultural trade, because global market mechanisms can strongly modulate the economic impacts of regional yield changes (Stevanovicet al., 2016; Hasegawa et al, 2018). We provide an assessment of model fidelity based on observed yields at the country level, and show some selected examples of the simulation output dataset to illustrate model responses across the input dimensions
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