Warmer growing seasons improve cereal yields in Northern Europe only with increasing precipitation

Abstract. Crop yields depend on climatic conditions such as precipitation and temperature and their timing before and during the growing season. At high latitudes, climate change could lengthen the growing season and provide more suitable temperatures, but also expose crops to more frequent damaging conditions. We quantified the response of regionally-averaged 1965–2020 winter and spring cereal yields in Sweden to a wide set of descriptors of climatic conditions. With statistical models, we explored the role of both short-term and average conditions over physiologically relevant developmental stages, as well as of a proxy of water availability during the period prior to the main growing season. Temperature and precipitation or dry spell lengths for the entire growing season explained 75–85 % of yield variability, performing better than short-term potentially damaging conditions. Low precipitation or extended dry spells combined with high temperatures and, conversely, high precipitation sums with cool temperatures decreased yields for all crops. Our findings suggest that under climate change crop yields will be reduced in Sweden, unless warming is accompanied by increase in precipitation during the main growing season. With unaltered or reduced growing season precipitation, benefiting from warmer temperatures caused by climate change will require adaptation measures.