Nighttime warming affects yields of major grain crops: A global meta-analysis

Current studies and future projections of climate change indicate an asymmetric warming characterized by a greater increase in nighttime temperatures relative to daytime temperatures. Warmer nights negatively impact crop yields, posing challenges for global food security. The effects of nighttime warming vary by crop species, developmental stages, regions, and experimental conditions. This meta-analysis synthesizes data from 59 studies (680 observations) on wheat, rice, maize, and soybean under controlled (i.e., greenhouses and growth chambers) and field conditions. Results show an average yield reduction of ∼25 % due to a mean nighttime warming of ∼4.5 °C, with rice (∼33 %) and wheat (∼21 %) being most affected, followed by maize (∼10 %), while soybean showed no significant changes. Yield losses were more pronounced under controlled conditions (∼41 %) than in field studies (∼10 %), likely due to differences in experimental setups and temperature intensities. Yield reductions were most significant during the critical periods of development for yield determination and grain-filling in wheat and rice, especially under higher warming intensities. Controlled studies reported higher yield penalties per °C increase in nighttime temperature compared to field studies: 4.7 % vs. 1.0 % in rice and 5.5 % vs. 0.5 % in wheat. These findings highlight the value of controlled experiments for understanding physiological impacts and assessing their mechanisms, but frequently overestimate yield penalties, emphasizing the need for more field-based approaches to represent real-world conditions better. This study underscores the urgency of standardizing experimental protocols and focusing research on major crops like maize and soybean, as well as other food-security crops like sorghum, millets, and legumes, in regions vulnerable to climate change. Incorporating advanced phenotyping, modeling, and field-adapted technologies will be crucial for developing effective adaptation, mitigation, and resilience strategies to combat nighttime warming’s impacts on global crop production.