Spatiotemporal variation of future heat damage of rice in the Middle and Lower Reaches of the Yangtze River using CMIP6 projections

Rice production can be significantly suffered from frequent heat damage with the ongoing climate change in recent years. For instance, the Middle & Lower Reaches of the Yangtze River play an important role in the single and double rice growing areas in China, with a yield and planting area of more than 1/3. Since the beginning of summer in 2022, the middle & lower reaches of the Yangtze River have suffered an unprecedentedly long period of extremely high temperature events, which can inevitably pose adverse effects on the rice growth stages. The estimations on the evolution of heat damage of rice in the future are beneficial to develop reliable strategies for climate change, particularly for national food security and agriculture sustainability. Furthermore, the prediction ability of extreme temperature can be expected to be improved using the latest Coupled Mode Intercomparison Project (CMIP6). In this study, the current and future (2015-2040, 2041-2060, 2061-2080, 2081-2100) was predicted to share the socioeconomic paths (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) in the spatiotemporal evolution characteristics of accumulated hot damage temperature for single and double rice. The bias-corrected processing was performed on the daily maximum temperature data from 14 climate models in CMIP6 by the grid observation data in the CN05.1 dataset from 1961 to 2000, and further combined with Bayesian model averaging (BMA). Results show that: 1) The bias correction significantly reduced the systematic bias of climate model data, whereas, the BMA effectively improved the reliability of CMIP6 projections. The CanESM5, IPSL-CM6A-LR, and MIROC6 accounted for a larger proportion, indicating a more accurate simulation of daily maximum temperature, compared with the rest. 2) Single rice and early rice were more susceptible to heat damage than late rice. Heat damage of the whole growth duration of rice was mainly distributed in the Jianghan Plain, the central Hunan hilly area, and the Poyang Lake Plain. There was more significant growth of accumulated hot damage temperature in these areas in the future. 3) Much more areas were exposed to heat damage, as the radiative forcing levels increased. The areas of single and early rice were projected to increase by more than 20℃•d during the 2090s under the SSP2-4.5 scenario, compared with the historical period. There was occupying over 1/3 areas, while the areas increased more than 60℃•d were over 80% under the SSP5-8.5 scenario. 4) The maximum increase of accumulated hot damage temperature in the whole growth period (booting-maturity) for the single, early, and late rice was projected to reach 70.8, 76.1, and 14.9℃•d, respectively during the 2090s. The heat damage increasing in single and late rice was concentrated in the booting to milking maturity, while the heat damage increasing in early rice was concentrated in the flowering to maturity. The change of accumulated hot damage temperature was less affected by climate change in the other growth stages. The finding can provide an important strong reference for rice production to better cope with climate change, particularly against the high-temperature disasters for national food security.