Impacts of 1.5 degrees C and 2.0 degrees C global warming above pre-industrial on potential winter wheat production of China

摘要

Keeping global temperatures below 2.0 degrees C above pre-industrial condition and pursuing efforts toward the more ambitious 1.5 degrees C goal in the late 21st century was the main target from the Paris Agreement in 2015. Here we assessed the likely challenges for the China's winter wheat production under 1.5 degrees C and 2.0 degrees C increase of global temperature, with four wheat crop models (CERES-Wheat, Nwheat, WheatGrow, and APSIM-Wheat) and the latest climate projections from the Half a degree Additional warming, Prognosis and Projected Impacts project (HAPPI). Instead of using average "winter type" wheat cultivar, and same management and soil inputs for whole region, location-specific winter wheat cultivars with local agronomic information were calibrated for each of the representative wheat growing area of China, allowing a better spatial agronomic representation of the whole wheat planting area. The mean growing season temperature (GST) during the winter wheat vegetative stage was projected to increase by 0.6 to 1.4 degrees C for the 1.5 degrees C scenario, and 0.9 to 1.8 degrees C for the 2.0 degrees C scenario, while during the reproductive stage was decreased between 0 and 0.9 degrees C for the 1.5 degrees C scenario and -0.3 and 1.1 degrees C for the 2.0 degrees C scenario. Growing season duration (GSD) for the whole period was shortened by 6 to 15 days for the 1.5 degrees C scenario and 8 to 18 days for the 2.0 degrees C scenario, as a result of higher GST under global warming. Increase in GST and decrease in GSD was more obvious in the Southwest Subregion (SWS) than subregions in the north. The shortening GSD for the whole wheat growth period was mostly from the shortening vegetative period, as no appreciable difference in number of days from anthesis to maturity was found for the whole regions. Although there is variability among models, the indication is that wheat yields were projected to increase in the North Subregion (NS), the Huang-Huai Subregion (HHS), and the Middle-lower Researches of Yangzi River Subregion (MYS), but to decrease in the SWS under two warming scenarios. The effects of elevated CO2 concentration were mostly beneficial and tended to offset the negative impacts of increasing temperature at both global warming scenarios, with a rate of 7-14% yield increase per 100-ppm, except for locations with GST of baseline higher than 11 degrees C. Aggregating to regional wheat production, the total winter wheat production of China was projected to increase by 2.8% (1.6% to 3.0%, 25th percentile to 75th percentile) and 8.3% (7.0% to 9.6%, 25th percentile to 75th percentile) under 1.5 degrees C and 2.0 degrees C scenarios, and most of increase was observed in the north subregions due to the largest wheat planting area. Our results will lay the foundation for developing adaptation strategies to future climate change to ensure China and global wheat supply and food security.