| 英文摘要: | Crop models are essential tools for assessing the threat of climate change to local and global food production1. Present models used to predict wheat grain yield are highly uncertain when simulating how crops respond to temperature2. Here we systematically tested 30 different wheat crop models of the Agricultural Model Intercomparison and Improvement Project against field experiments in which growing season mean temperatures ranged from 15 °C to 32 °C, including experiments with artificial heating. Many models simulated yields well, but were less accurate at higher temperatures. The model ensemble median was consistently more accurate in simulating the crop temperature response than any single model, regardless of the input information used. Extrapolating the model ensemble temperature response indicates that warming is already slowing yield gains at a majority of wheat-growing locations. Global wheat production is estimated to fall by 6% for each °C of further temperature increase and become more variable over space and time. Understanding how different climate factors interact and impact food production3 is essential when reaching decisions on how to adapt to the effects of climate change. To implement such strategies the contribution of various climate variables on crop yields need to be separated and quantified. For instance, a change in temperature will require a different adaptation strategy than a change in rainfall4. Temperature changes alone are reported to have potentially large negative impacts on crop production5, and hotspots—locations where plants suffer from high temperature stress—have been identified across the globe6, 7. Crop simulation models are useful tools in climate impact studies as they deal with multiple climate factors and how they interact with various crop growth and yield formation processes that are sensitive to climate. These models have been applied in many studies, including the assessment of temperature impacts on crop production1, 8. However, none of the crop models have been tested systematically against experiments at different temperatures in field conditions. Although many glasshouse and controlled-environment temperature experiments have been described, they are often not suitable for model testing as the heating of root systems in pots9 and effects on micro-climate differ greatly from field conditions10. Detailed information on field experiments with a wide range of sowing dates and infrared heating recently became available for wheat11, 12. Such experiments are well suited for testing the ability of crop models to quantify temperature responses under field conditions. Testing the temperature responses of crop models is particularly important for assessing the impact of climate change on wheat production, because the largest uncertainty in simulated impacts on yield arises from increasing temperatures2. In a ‘Hot Serial Cereal’ (HSC) well-irrigated and fertilized experiment with a single cultivar, the observed days after sowing (DAS) to maturity declined from 156 to 61 days when growing season mean temperatures (Tmean) increased from 15 °C to 26 °C (Fig. 1a, b). The performances of individual models are illustrated in Supplementary Fig. 3. Note that simulations were carried out in a ‘blind’ test (modellers had access to phenology and yield data of one of the treatments only (normal temperature); see Supplementary Methods). Higher temperatures thus decreased the number of days during which plants could intercept light for photosynthesis, with consequent reductions in biomass (Supplementary Fig. 5) and grain yields (Fig. 1). When Tmean was >28 °C and when there were extremely high temperatures early in the growing season with many days of maximum temperature (Tmax) > 34 °C, a critical maximum temperature for wheat13, crops did not reach anthesis or grain set, so it was not possible to record anthesis or maturity dates and the yields were zero (Fig. 1a–c and Supplementary Fig. 6a–c). Observed grain yields declined from about 8 t ha−1 when Tmean was 15 °C to zero when Tmean was >28 °C (Fig. 1c).
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