Spatiotemporal asymmetry in temperature amplitude and its impact on rice in Asia

Temperature asymmetry and its impact on rice

Abstract

Over half of the world's population relies on rice as a staple food, with Asia accounting for about 90% of both its production and consumption, making it central to global food security. Climate warming has increasingly altered the diurnal temperature range (DTR), with night-time temperatures rising faster than day-time temperatures, leading to pronounced diurnal asymmetry. This asymmetric warming shortens rice growth duration, increases spikelet sterility, reduces grain-filling period, and heightens respiratory losses, ultimately lowering grain yield and quality. Over the course of the 20th century, global average surface temperatures rose sharply, with warming rates nearly doubling in the latter half, largely due to anthropogenic activities. Climate data indicate that night-time temperatures are rising more rapidly than day-time temperatures-globally, at 1.4 times the rate, affecting more than half of the Earth's land surface between 1983 and 2017. Night-time heat is particularly harmful for rice; even a 1°C increase above the critical night-time threshold (~24°C) can cut grain yield and biomass by up to 10%. Elevated night-time temperatures during the reproductive stage disrupt respiration, nutrient translocation, and biomass allocation, and degrade grain quality, causing defects like chalky kernels-often more severely than high day-time temperatures. Despite this, yield declines are often attributed solely to night heat, overlooking broader effects of asymmetric warming. Given the variability in temperature patterns across time and regions, there is an urgent need for targeted strategies, such as breeding high-temperature-tolerant rice varieties, reducing heat-induced yield losses, and safeguarding future food security.