Critical increase in the occurrence of heat stress during reproductive growth in Russian wheat beyond 1.5 C global warming

Abstract

Exposure to a critical high temperature during the reproductive period can harm wheat development, entail yield losses and lead to yield instability. In the recent past, Russian wheat production suffered a few times from marked downturns caused by heat waves that eventually had repercussions on the global wheat market. In this study, we assess the frequency of heat stress days on Russian spring and winter wheat production using climate scenarios generated from five general circulation models and reflecting four emission scenarios. We find that the fraction of cultivated area characterized by a significant positive trend in risk increases sharply if global warming exceeds 1.5 °C targeted by the Paris Agreement. Currently particularly affected areas are the main cultivation regions in the southern Urals and southern Siberia (spring wheat) and southern European Russia (winter wheat). In scenarios not foreseeing mitigation, conditions comparable to those experienced in 2010, considered here as a critical year, could become rather common in the future. We estimated that the probability of incurring in a critical year within a 30-year time window could reach 40–60% (spring wheat), respectively 20-40% (winter wheat) during the second half of the century, over most of the Russian territory. Our analysis suggests that expansion of the cultivation area towards more northern latitudes is not sufficient to prevent risk associated with heat waves, suggesting the need for other measures of adaptation to sustain production and stabilize yield.