Global warming may reduce rice production far more than current agricultural and climate models suggest, according to a new study led by Yiwei Jian of Peking University and the Helmholtz Centre for Environmental Research (UFZ), published in Science Advances. The researchers estimate that every 1°C increase in global mean temperature could cut worldwide rice yields by 8.1%—more than double the losses projected by existing models.
The findings carry major implications because rice is the staple food for more than half of the world’s population. While its vulnerability to climate change has long been recognized, estimates of future yield losses have varied widely. According to the authors, one key reason is that many models fail to distinguish between the effects of rising average temperatures and those of short-lived episodes of extreme heat.
To address this gap, the researchers assembled the largest field-warming database ever compiled for rice, combining 214 observations from published studies with new field experiments conducted across 12 growing sites in China. This allowed them to isolate the effects of high temperatures at different stages of the plant’s development.
Their analysis shows that the greatest damage comes not from gradual warming itself but from exposure to hot days with temperatures between 30°C and 35°C, and especially above 35°C. During the reproductive stage, a single additional day above 30°C reduces yields by between 1.1% and 1.8%. By contrast, extreme heat during the vegetative stage has a much smaller impact. High temperatures primarily disrupt grain formation and the allocation of biomass to developing kernels rather than limiting the plant’s overall growth.
When the team compared these findings with seven leading global crop models, they found that nearly all of them underestimate the effects of extreme heat. Current models predict yield losses of only 0.1% to 1.3% for each additional hot day, well below the values observed in field experiments. Correcting for this bias raises the estimated global yield decline associated with 1°C of warming from 3.8% to 8.1%.
South Asia and Southeast Asia emerge as the regions most at risk. In Pakistan, India and Bangladesh, projected yield losses increase from 2.1% to 6.6%, while estimates for Thailand, the Philippines and Myanmar rise from 3.7% to 7.7%. The revisions are smaller for China and Japan.
The authors argue that these findings call for a reassessment of global food security projections and highlight the need for crop models that better capture the impact of extreme heat events. They also stress the urgency of developing heat-tolerant rice varieties, improving irrigation practices and enhancing soil management, particularly in tropical regions where climate change is expected to have the greatest impact on food production.
