不同升温阈值下中国地区极端气候事件变化预估

本文基于耦合模式比较计划第五阶段(CMIP5)的18个全球气候模式的模拟结果,预估了全球平均气温在不同典型浓度路径(RCPs)下达到2℃、3℃和4℃阈值时,中国地区气温和降水的变化,并采用了具有稳定统计意义的27个极端气候指标定量评估了全球平均气温达到不同阈值时,中国地区极端气候事件的可能变化。结果表明,未来我国平均气温增幅将高于全球平均增暖,极端暖事件(如暖夜、暖昼、热带夜)明显增多,达到4℃阈值时,暖夜指数相比参考时段增加约49.9%。极端冷事件(如冷夜、冷昼、霜冻)减少。随全球气温升高,中国北方平均降水增多。在不同升温阈值下,中国地区降水的极端性都体现出增强的趋势,强降水事件发生频率(如中雨日数、大雨日数)和强度(如五日最大降水量、极端强降水量)都明显增加。随升温阈值的升高,这些变化幅度更大,在 RCP8.5 情景下全球升温 3℃和4℃时,中国平均五日最大降水分别增加 12.5mm和17.0mm。我国西南地区极端降水强度的增幅高于其他地区。

Changes in Climate Extremes over China in a 2°C, 3°C,and 4°C Warmer World

Due to human-induced global warming, global Average Surface Air Temperature (ASAT) will reach certain thresholds with reference to the pre-industrial period. Quantitative assessments of climate extremes across China when reaching these thresholds are important indicators in disaster risk management and policymaking. In this study, based on outputs of 18 General Circulation Models (GCMs) from the Coupled Model Intercomparison Project Phase 5 (CMIP5), 27 climate-extreme indices computed with a consistent methodology are used to quantify the changes in the mean and extreme climate across China when the 2°C, 3°C, and 4°C thresholds under different Representative Concentration Pathways (RCP) scenarios are exceeded. In general, the ASAT warms faster over China than the global mean in the 21st century. Extreme warm events (e.g., warm nights, warm days, and tropical nights) increase greatly, while extreme cold events (e.g., cold nights, cold days, and frost days) decrease. When the 4°C threshold is exceeded, warm nights index (spatially averaged over China) are projected to show an increase of about 49.9% relative to the reference period. Accompanied by the increase in global mean temperature, the northern part of China will see more precipitation when the 2°C threshold is exceeded. Extreme precipitation shows obvious intensification in both frequency and magnitude when different temperature thresholds are exceeded. China is dominated by lengthening heavy and very heavy precipitation days and increasing maximum consecutive 5-day precipitation and extremely wet days. Under the RCP8.5 scenario, the maximum consecutive 5-day precipitation amount increases by 12.5 mm and 17.0 mm when the global ASAT becomes 3°C and 4°C warmer, respectively. The changes are found to be more pronounced under higher temperature thresholds. Southwest China, however, exhibits larger changes in the magnitude of extreme precipitation than other regions.