Modelling impacts of climate change on wheat yields in England and Wales: assessing drought risks

With global warming, evapotranspiration (ET) is likely to increase and, with more variable rainfall, droughts could occur more often. Our objective was to evaluate the impact of climate change on drought indicators and yield of winter wheat in England and Wales. We used the crop simulation model Sirius to assess the effect of changing climate on maximum soil moisture deficit (SMDmax), drought-related reduction of potential yield (YRdr) and wheat yields. Climate scenarios were based on the output from the Hadley Centre Climate Model (HadCM2) and were constructed by using a stochastic weather generator (LARS-WG). Weather was generated for the baseline (1960–1990) and future (2020s and 2050s) periods at representative sites in the UK using two types of scenarios: (1) those incorporating only mean changes in climate variables and (2) those incorporating changes in means and variance. Probability distributions were derived from multiple simulations using representative weather, soil types and sowing dates. SMDmax is likely to increase in the future, especially on shallow soils, and the probability of YRdr exceeding 25% will increase by 10% until the 2050s. However, average wheat yields are likely to increase by 1.2 to 2 t/ha (15–23%) by the 2050s because of a CO2-related increase in radiation use efficiency (RUE). Grain yields are likely to be less variable but the probability of the annual coefficient of variation (CV) exceeding 15% remains the same. Changes in the variance of weather variables will have little effect on grain yields. Ignoring genetic improvement in varieties, yields are predicted to increase more until the 2020s than in the following 30 years. A sensitivity analysis for crop growth parameters suggests that further yield gains (1 t/ha) are possible with new varieties that increase the grain filling period.