Editing IPCC:AR6/WGI/Chapter-Atlas (section)

==== Atlas.5.1.2 Assessment and Synthesis of Observations, Trends and Attribution ====

<div id="h3-15-siblings" class="h3-siblings"></div>

Summer (June–August) mean temperature in eastern China has increased by 0.82°C since reliable observations were established in the 1950s ( [[#Sun--2014|Sun et al., 2014]] ). Based on historical meteorological observations, the best estimate of the linear trend of annual mean surface air temperature (SAT) for China with 95% uncertainty ranges is 0.38°C ± 0.05°C per decade for 1979–2015 ( [[#Li--2017|Li et al., 2017]] ). From 1960 to 2010, theincreasing trend of temperature was about 0.34°C per decade in the arid region of north-west China, higher than the average over China ( [[#Li--2012|]] [[#Li--2012|B. Li et al., 2012]] ; [[#Xu--2015|Xu et al., 2015]] ). Over South Korea, warming is 1.4–2.6 times larger than global trends. The increase is 1.90°C during 1912–2014 and 0.99°C during 1973–2014 ( [[#Park--2017|Park et al., 2017]] ) with a 25–45% urbanization contribution. The annual temperature increased in large cities at a rate of 0.29°C ± 0.08°C per decade compared with 0.11°C ± 0.08°C per decade in other stations in South Korea from 1960 to 2010 (H.-S. [[#Kim--2016|]] [[#Kim--2016|Kim et al., 2016]] ). A relatively high increase in annual mean temperature at the rate of 3.0°C per century was detected in the Tokyo metropolitan area for the period 1901–2015 ( [[#Matsumoto--2017|Matsumoto et al., 2017]] ). Trends of annual temperature for the period of 1961–2015 are shown in Figure Atlas.11. Most areas of East Asia have significant warming trends exceeding 0.1°C per decade, and the strongestwarming (0.3°C–0.4°C per decade) occurs in northern China.

Observational studies indicated significant decadal variations in the EAWM ( [[#Wang--2016|Wang and Lu, 2016]] ; [[#He--2017|He et al., 2017]] ). It weakened significantly around the late 1980s, being relatively strong during 1976–1987 and weaker during 1988–2001. The EAWM has recovered in intensity after 2004 and caused frequent and prevalent severe cold spells, as well as a number of unusually harsh cold winters in many parts of East Asia during the period 2004–2012 ( [[#Wang--2014|Wang and Chen, 2014]] ; [[#Kug--2015|Kug et al., 2015]] ; [[#Ge--2016|Ge et al., 2016]] ; [[#Gong--2018|Gong et al., 2018]] ). Negative zonal mean winter SAT anomalies were observed over the whole of East Asia from 1980 to 1988, with positive anomalies observed over high and low latitudes from 1988 to 2010 ( [[#Miao--2020|Miao and Wang, 2020]] ).

Precipitation trends over East Asia show considerable regional differences ( ''medium confidence'' ). Mean precipitation has shown negligible sensitivity to the warming trend with consequently limited overall trends in China though summer rainfall daily frequency and intensity show respectively decreasing and increasing trends from 1961 to 2014 ( [[#Zhou--2017|Zhou and Wang, 2017]] ). The summer precipitation trends over eastern China display a dipole pattern, characterized by positive anomalies in central-eastern China along the Yangtze River Valley and negative anomalies in north China since the 1950s ( [[IPCC:Wg1:Chapter:Chapter-8#8.3.2.4.2|Section 8.3.2.4.2]] ). This pattern has changed with the enhanced rainfall in the Huaihe River Valley and decreased in the regions south of the middle and lower reaches of the Yangtze River Valley since the 2000s ( [[#Liu--2012|Liu et al., 2012]] ; [[#Zhao--2015|Zhao et al., 2015]] ). The climate in north-west China changed from ‘warm–dry’ to ‘warm–wet’ condition in the mid-1980s ( [[#Peng--2017|Peng and Zhou, 2017]] ; [[#Wang--2020|Wang et al., 2020]] ), with an increased rate of annual precipitation of about 3.7% per decade from 1961 to 2015 (P. [[#Wu--2019|]] [[#Wu--2019|Wu et al., 2019]] ) and 11.2 mm per decade between 1960 and 2011 in northern Xinjiang ( [[#Xu--2015|Xu et al., 2015]] ). Mean rainfall and the number of rainy days during the Meiyu-Baiu-Changma period from June to September have increased during 1973–2015 in Korea ( [[#Lee--2017|Lee et al., 2017]] ). The precipitation trend has caused a large increase in summer precipitation at a rate of 40.6 ± 4.3 mm per decade, resulting in an increase of annual precipitation of 27.7 ± 5.5 mm per decade in South Korea from 1960 to 2010 (H.-S. [[#Kim--2016|]] [[#Kim--2016|Kim et al., 2016]] ). Precipitation amounts exhibited a slight decrease at both the annual and seasonal scales in Japan for the period 1901–2012 ( [[#Duan--2015|Duan et al., 2015]] ).

Agriculture intensification through oasis expansion in Xinjiang region has increased summer precipitation in the Tian Shan mountains ( ''high confidence'' from ''medium evidence'' with ''high agreement'' ) ( [[#Zhang--2009|Zhang et al., 2009]] , 2019b; [[#Deng--2015|Deng et al., 2015]] ; [[#Guo--2015|Guo and Li, 2015]] ; [[#Yao--2016|Yao et al., 2016]] ; [[#Xu--2018|Xu et al., 2018]] ; [[#Cai--2019|Cai et al., 2019]] ). However, there is ''very low confidence'' of the effect of oasis expansion on the temperature warming trend ( [[#Han--2013|Han and Yang, 2013]] ; [[#Li--2013|Li et al., 2013]] ; [[#Yuan--2017|Yuan et al., 2017]] ).

In the context of climate warming, intense snowfalls have hit China frequently in recent winters and have caused severe damages to the sustainability of society ( [[#Sun--2019|Sun et al., 2019]] ). Observations generally show a decrease in the frequency and an increase in the mean intensity of snowfalls in north-western, north-eastern and south-eastern China and the eastern Tibetan Plateau since the 1960s ( [[#Zhou--2018|Zhou et al., 2018]] ), but the results may depend on the objective criteria for identifying winter snowfall (J. [[#Luo--2020|]] [[#Luo--2020|Luo et al., 2020]] ).

<div id="Atlas.5.1.3" class="h3-container"></div>

<span id="atlas.5.1.3-assessment-of-model-performance"></span>