UC Berkeley

Responses of global crop yields to warmer temperatures are fundamental to sustainable development under climate change but remain uncertain. Here, we combined a global dataset of field warming experiments (48 sites) for wheat, maize, rice and soybean with gridded global crop models to produce field-data-constrained estimates on responses of crop yield to changes in temperature (ST) with the emergent-constraint approach. Our constrained estimates show with >95% probability that warmer temperatures would reduce yields for maize (−7.1 ± 2.8% K−1), rice (−5.6 ± 2.0% K−1) and soybean (−10.6 ± 5.8% K−1). For wheat, ST was 89% likely to be negative (−2.9 ± 2.3% K−1). Uncertainties associated with modelled ST were reduced by 12–54% for the four crops but data constraints do not allow for further disentangling ST of different crop types. A key implication for impact assessments after the Paris Agreement is that direct warming impacts alone will reduce major crop yields by 3–13% under 2 K global warming without considering CO2 fertilization effects and adaptations. Even if warming was limited to 1.5 K, all major producing countries would still face notable warming-induced yield reduction. This yield loss could be partially offset by projected benefits from elevated CO2, whose magnitude remains uncertain, and highlights the challenge to compensate it by autonomous adaptation.