The Fingerprint of Climate Trends on European Crop Yields

Europe has experienced a stagnation of some crop yields since the early-1990s as well as statistically-significant warming during the growing-season. While it has been argued that these two are causally connected, no previous studies have formally attributed long-term yield trends to a changing climate. Here we present two statistical tests based on the distinctive spatial pattern of climate change impacts and adaptation, and explore their power under a range of parameter values. We show that statistical power for the identification of climate change impacts is high in many settings, but that power for identifying adaptation is almost always low. Applying these tests to European agriculture, we find evidence that long-term temperature and precipitation trends have reduced continent-wide wheat, maize, and barley yields by 2.7%, 1.1%, and 3.9%, and have increased sugarbeet yields by 1.0%. This can account for approximately 10% of the yield stagnation in Europe, with changes in agricultural and environmental policies likely explaining the remainder.