低排放情景下全球极端气候事件变化在温升过冲前后达到1.5℃的差异

The differences of global extreme climate events changes before and after 1.5℃overshoot

基于耦合模式比较计划第六阶段(CMIP6)全球气候模式在SSP1-1.9温室气体排放情景下的模拟结果,预估了全球平均气温相对于工业化前达到1.5℃温升(P1阶段)后继续增暖然后再次返回(过冲)到1.5℃温升时的(P2阶段)全球气温、降水及极端气候指数的可能变化,并且分析其预估不确定性。结果表明:P1和P2两阶段间气温、降水及极端气候的多模式一致的差异在全球各分区广泛出现,且区域性和局地性特征明显。各指标表征的多模式一致的极端温度变化普遍接近或者超过全球陆地面积的15%。极端低温的P1和P2两阶段差异的空间分布与冬季平均气温差异的空间分布有一定相似度,极端高温变化的分布则更凸显局地性。全球范围内低温和高温多模式一致增加的面积都高于其减少的面积,预计欧亚大陆中高纬的西部、北美洲、中国东北等区域的低温风险以及青藏高原、中国东部、南亚、东非、北美洲、南极洲等区域的高温风险会升高。各指标表征的多模式一致的极端降水变化普遍超过全球陆地面积的20%,其中增加与减少的面积接近。强降水差异的分布特征与年降水的有部分相似,一致增多主要分布在中国南方、南亚、东南亚、南美洲东部和西南端、北美、澳洲和中东欧的部分地区等,一致减少主要分布在中国华北到东北、青藏高原南麓、非洲南部、南美洲北部和澳洲北部等。连续干旱日数在多数区域表现为增多,集中且连续地分布在中亚、南亚、青藏高原、俄罗斯中北部、非洲撒哈拉以北和中部、澳洲中部、南极洲部分地区等。这些都表明即使全球在2030年前达到碳排放峰值,并立即开始减少碳排放,但由于各个区域气候对全球变暖的响应有明显差异,温升过冲后部分区域的极端事件发生频率并未及时回退到过冲前的水平,需警惕区域和局地尺度气象灾害及其影响的增加。

Based on global climate models from Coupled Model Intercomparison Projection Phase 6(CMIP6)under SSP1-1.9 scenario,the changes in mean temperature and precipitation,as well as seven extreme climate indices,over the 23 subregions at 1.5℃level(P1 phase)and cooled to 1.5℃level(P2 phase)were projected.Results show that the differences of temperature,precipitation,and extreme climate events between P1 and P2 phases show good agreement worldwide among multiple models,with obvious regional and local features.Multi-model consistent changes in temperature extremes generally approach or exceed 15%of the global land area.The spatial pattern of extreme cold events differences between two phases is similar to that of winter mean temperature,and the distribution of extreme hot events shows the local character.Globally,the areas with multi-model consistent increases in both cold and hot events are larger than those with the decreases.The risk of extreme cold/hot events will increase over the western part of mid-high latitudes in Eurasia,North America and northeastern China/the Tibet Plateau,eastern China,South Asia,East Africa,North America and Antarctic.Multi-model consistent changes in precipitation extremes generally exceeds 20%of global land area,but the area with increases is close to that with decreases.The spatial pattern of heavy precipitation differences is partially similar to that of annual mean precipitation:the values over southern China,South Asia,Southeast Asia,eastern and southwestern South America,North America,Australia,and central and eastern Europe will increase with good agreement,and the values over North China to northeastern China,southern edge of the Tibet Plateau,southern Africa,northern South America and northern Australia will decrease with good agreement.More consecutive dry days(CDDs)are projected in most regions,the large changes with good agreement can be found over Central Asia,South Asia,the Tibet Plateau,central and northern Russia,north of Sahara in Africa and central Africa,central Australia,parts of Antarctic.It indicates that even if global carbon emission peaks before 2030 and then begins to reduce immediately,temperature and precipitation extremes at certain regions will be even larger than those before overshooting,due to the diverse regional climate responses to global warming.Then the impact will still last many years,with the influence increasing.Thus,the projected increases in extreme climate events on regional and local scale should be alerted.