Assessing agricultural risks of climate change in the 21st century in a global gridded crop model intercomparison

Abstract

Here we present the results from an intercomparison of multiple global gridded crop models (GGCMs) within the framework of the Agricultural Model Intercomparison and Improvement Project and the Inter-Sectoral Impacts Model Intercomparison Project. Results indicate strong negative effects of climate change, especially at higher levels of warming and at low latitudes; models that include explicit nitrogen stress project more severe impacts. Across seven GGCMs, five global climate models, and four representative concentration pathways, model agreement on direction of yield changes is found in many major agricultural regions at both low and high latitudes; however, reducing uncertainty in sign of response in mid-latitude regions remains a challenge. Uncertainties related to the representation of carbon dioxide, nitrogen, and high temperature effects demonstrated here show that further research is urgently needed to better understand effects of climate change on agricultural production and to devise targeted adaptation strategies.

Keywords: AgMIP; ISI-MIP; agriculture; climate impacts; food security.

Fig. 1.

Mean relative yield change (%) from reference period (1980–2010) compared to local mean temperature change (°C) in 20 top food-producing regions for each crop and latitudinal band. Results shown for the 7 GGCMs (6 for rice) for all GCM combinations of RCP8.5 compared to results from IPCC AR4 (represented as orange dots and quadratic fit; 36). Quadratic least-squares fits are used to estimate the general response for the GGCMs with explicit nitrogen stress (EPIC, GEPIC, pDSSAT, and PEGASUS; red line) and for those without (GAEZ-IMAGE, LPJ-GUESS, and LPJmL; green line). The 15–85% range of all models for each ¼°C band is represented in gray. Limits of local temperature changes reflect differences in projected warming in current areas of cultivation.

Fig. 2.

Average reference period (1980–2010) GGCM maize yield (A–F, H), rescaled to a common global average to make the spatial patterns more apparent, and historical yield M3 observation set (G) (39). Note that because some models are calibrated and others are not and because some models simulate potential rather than actual yields, it is not advisable to compare the absolute yields in the ensemble with observations.

Fig. 3.

Median yield changes (%) for RCP8.5 (2070–2099 in comparison to 1980–2010 baseline) with CO₂ effects over all five GCMs x seven GGCMs (6 GGCMs for rice) for rainfed maize (35 ensemble members), wheat (35 ensemble members), rice (30 ensemble members), and soy (35 ensemble members). Hatching indicates areas where more than 70% of the ensemble members agree on the directionality of the impact factor. Gray areas indicate historical areas with little to no yield capacity. The bottom 8 panels show the corresponding yield change patterns over all five GCMs x four GGCMs with nitrogen stress (20 ensemble members from EPIC, GEPIC, pDSSAT, and PEGASUS; except for rice which has 15) (Left); and 3 GGCMs without nitrogen stress (15 ensemble members from GAEZ-IMAGE, LPJ-GUESS, and LPJmL).

Fig. 4.

Relative change (%) in RCP8.5 decadal mean production for each GGCM (based on current agricultural lands and irrigation distribution) from ensemble median for all GCM combinations with (solid) and without (dashed) CO₂ effects for maize, wheat, rice, and soy; bars show range of all GCM combinations with CO₂ effects. GEPIC, GAEZ-IMAGE, and LPJ-GUESS only contributed one GCM without CO₂ effects.

Fig. 5.

Absolute deviation of decadal average production changes from ensemble median yield changes (as fraction of 1980–2010 reference period mean production) for all GCM × GGCM combinations in RCP2.6 (dark blue), RCP4.5 (light blue), RCP6.0 (orange), and RCP8.5 (red) for maize, wheat, rice, and soy with (Upper) and without (Lower) CO₂ effects. Simulations in A with CO₂ effects included five GCMs and seven GGCMs (35 members), whereas GAEZ-IMAGE, GEPIC, and LPJ-GUESS ran only a single GCM without CO₂ effects, resulting in 23 members in B.