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

==== Atlas.5.1.1 Key Features of the Regional Climate and Findings From Previous IPCC Assessments ====

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===== Atlas.5.1.1.1 Key Features of the Regional Climate =====

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The climatic regions defined for East Asia include central and eastern China, Japan and the Korea Peninsula (regions ECA and EAS in Figure Atlas.1 7). East Asia is significantly influenced by monsoon systems ( [[IPCC:Wg1:Chapter:Chapter-8#8.3.2.4.2|Section 8.3.2.4.2]] ). The seasonal advance or retreat of the East Asian summer monsoon (EASM) rainband is crucial to local climate. The East Asian winter monsoon (EAWM) has significant influence on the weather and climate over East Asia and plays an important role in regulating winter temperatures including strong cold events and snowstorms ( [[#Wang--2014|Wang and Chen, 2014]] ; [[#Wang--2016|Wang and Lu, 2016]] ). The East Asian monsoons exhibit considerable variability on a wide range of time scales, including notable interannual variabilities that includes an effect of the El Niño–Southern Oscillation (ENSO; [[#Wang--2000|Wang et al., 2000]] ) and the Indian Ocean Dipole (IOD; [[#Takaya--2020|Takaya et al., 2020]] ), and significant inter-decadal variabilities in the 20th century resulted from the effect of Pacific Decadal Variability (PDV; [[#Zhou--2009|Zhou et al., 2009]] ), see also [[IPCC:Wg1:Chapter:Annex-iv|Annex IV]] and Table Atlas.1. The thermal conditions of both the Tibetan Plateau and related ocean regions play key roles in modulating the intensity of the monsoon circulation. The East Asian monsoons are mainly driven by land–sea thermal contrast and, thus, are deeply affected by global climate change ( [[#Ding--2014|Ding et al., 2014]] ; [[#Gong--2018|Gong et al., 2018]] ).

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===== Atlas.5.1.1.2 Findings From Previous IPCC Assessments =====

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The findings of the IPCC AR5 ( [[#Christensen--2013|Christensen et al., 2013]] ) stated that the EASM and EAWM circulations have experienced an inter-decadal scale weakening since the 1970s, leading to a warmer climate in winter and enhanced mean precipitation along the Yangtze River Valley (30°N) but deficient mean precipitation in northern China in summer. Since the middle of the 20th century, it is ''likely'' that there has been an increasing trend in winter temperatures across much of Asia ( [[#Christensen--2013|Christensen et al., 2013]] ). The numbers of cold days and nights have decreased and the numbers of warm days and nights have increased over Asia ( [[#Hartmann--2013|Hartmann et al., 2013]] ). It is ''likely'' that there are decreasing numbers of snowfall events where increased winter temperatures have been observed ( [[#Hartmann--2013|Hartmann et al., 2013]] ). The SRCCL reports a land-use-change-induced cooling as large as –1.5°C in eastern China between 1871 and 2007 ( [[#Hartmann--2013|Hartmann et al., 2013]] ). The summer rainfall amount over East Asia shows no clear trend during the 20th century.

The IPCC AR5 ( [[#Christensen--2013|Christensen et al., 2013]] ) reports a significant increase in mean temperatures in south-eastern China, associated with a decrease in the number of frost days under the SRES A2 emissions scenario. The CMIP5 model projections indicate an increase of temperature in both boreal winter and summer over East Asia for RCP4.5. Based on CMIP5 model projections, there is ''medium confidence'' in an intensified EASM and increased summer precipitation over East Asia. More than 85% of CMIP5 models show an increase in mean precipitation of the EASM, while more than 95% of models project an increase in heavy precipitation events ( [[#Christensen--2013|Christensen et al., 2013]] ).The SROCC states that future projections of annual precipitation indicate increases of the order of 5–20% over the 21st century in many mountain regions, including the Himalaya and East Asia ( [[#Hock--2019b|Hock et al., 2019b]] ). The SR1.5 reports that statistically significant changes in heavy precipitation between 1.5°C and 2°C of global warming are found in East Asia ( [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ).

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