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Lanzhou University (2019)

Climate Change over East-central Asia under the Global Warming Limits of 1.5℃ and 2℃

张萌;

Titre : Climate Change over East-central Asia under the Global Warming Limits of 1.5℃ and 2℃

Auteur : 张萌;

Grade : Master’s Theses 2019

Université : Lanzhou University

Résumé
East Asia-Central Asia is one of most sensitive regions to climate changes because of its significant sea-land thermal differences,complex terrain conditions and fragile ecological environment.Since the industrial revolution,the temperature increase rate in East Asia-Central Asia has always been higher than the global average level,which has led to the frequency of extreme climate events in this region and the intensification of drought.The Paris Climate Change Conference reached a consensus to keep the global average warming within 2℃ compared with the temperature rise in the pre-industrial period,and has been working to keep the temperature rise within1.5 ℃.The climate response of East Asia-Central Asia under these two warming targets is of vital interest to the billions of people living here.This study,based on the consequence of three groups of 1.5℃ and 2℃ experiments simulated by the Community Earth System Model,evaluated the extreme temperature,extreme precipitation and drought expansion in East Asia-Central Asia in detail and quantitatively.The results are as follows:First,the number of frost days and ice days that characterize the frequency of extreme temperature cold events decrease more rapidly in arid and semi-arid regions,by approximately 10 days(1.5℃)and 15 days(2℃)compared to the historical period(1971-2000)respectively.The summer days and tropical nights occur more frequently in humid areas,especially in southeastern China.Under 1.5℃ target,the increase of intensity indices is equal to the average temperature warming response(1.5℃),while the additional 0.5℃ warming makes the response of intensity indices increase as high as 0.8-1.0℃.There is no significant difference between arid and semi-arid areas and humid areas.In winter,the temperature increase is 0.2-0.4℃ higher than that in summer.The daily temperature range will experience a 0.3-0.5℃ increase in dry-wet transition zone in summer because of the additional global warming of 0.5℃.Most humid areas are projected to experience a 0.5℃ increase in winter,On the contrary,a0.2-0.5℃ decrease will occur in arid and semi-arid areas.This change is closelyrelated to the distribution of cloud cover and precipitation.Second,all the three selected extreme precipitation indices(Rx1day,Rx5 day,R95p)will significantly increase under the 1.5℃ warming limit compared to historical period,especially in the southeastern China and the Tibetan Plateau.There is a accelerated increase of extreme precipitation response to a additional 0.5℃ warming.Humid areas are projected to experience more increase in absolute value and area fraction,whereas arid and semi-arid areas may have a larger probability ratio and a higher potential risk.There is projected to be over 200 mm increase in the amplitude of R95 p in a 1.5℃ future and a further 100 mm increase in 2℃ relative to1.5℃ in southeastern China and Himalayas.Moreover,the proportion of extreme precipitation in total precipitation will increase about 10%-20%.Extreme precipitation events may cause more flooding risks under 1.5℃ and 2℃ warming limits.Third,the results show that the additional 0.5℃ warming would lead to the positive change in both precipitation(by 1.78%)and potential evapotranspiration(by2.92%).Aridity index is projected to decrease slightly(by-0.99%),especially in arid and semi-arid areas(-1.18%)and dry-wet transition zone due to the faster increase in potential evapotranspiration compared with precipitation.Surface air temperature and precipitation are two dominate factors affecting aridity index in arid and semi-arid areas.In humid areas,the influence of humid area and precipitation is twice as much as the temperature(-63% to 31%).Other three factors play a relatively weak role in aridity index variation,the total sum of the three is less than 10% in both arid and semi-arid areas and humid areas.Moreover,under the additional 0.5℃ warming,all meteorological elements have changed significantly in areas with fragile ecological environment and extremely sensitive climate change such as the Qinghai-Tibet Plateau.

Mots clés : extreme temperature; extreme precipitation; aridity index; 1.5℃ and 2℃ warming limits; East Asia-Central Asia;

Présentation (CNKI)

Page publiée le 20 mars 2020