Amplified agricultural impacts from increasingly sequential heat extremes

As the climate warms, interacting weather extremes such as sequential heat events pose complex risks to societies. Regarding the global food system, laboratory experiments suggest that crop exposure to spring heat may either confer tolerance or enhance vulnerability to subsequent summer heat events. We show, under historic conditions that hot springs benefit crop yield but amplify the impacts of summer heat by 3% to 36% across crops and regions compared to average spring conditions. This increasing sensitivity results in impacts outweighing hot spring benefits when summer temperature anomalies exceed 2-4°C. Analyzing projected temperature increases, we find an eight-fold rise in the frequency of sequential heat extremes under the Shared Socioeconomic Pathway 3-7.0. Accounting for the compounding effect of sequential heat on crop yields increases projected losses by 1 to 71% depending on crop and region. This underlines the emerging nonlinear risk of sequential heat extremes to food security, which can largely be avoided when limiting warming to 1.5°C globally.