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

==== Atlas.5.1.4 Assessment and Synthesis of Projections ====

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The development of climate models provides a solid basis for projection of future monsoon changes under different global warming scenarios. Coupled model simulations indicate that East Asia and the Tibetan Plateau will ''likely'' experience higher warming than the global mean conditions across all global warming levels (Figure Atlas.1 7) and with the projected warming greater in ECA and TIB than EAS. Also, in the CMIP6 ensemble, the multi-model mean and 90th percentile warming for a given period and emissions scenario are consistently greater than in the CMIP5 ensemble. Larger warming magnitudes are projected to occur in the southern, north-western, and north-eastern regions of China, parts of Mongolia, the Korean Peninsula, and Japan than in other regions ( [[#Li--2018a|Li et al., 2018a]] ). Projections indicate winter increases in SAT over the East Asian continent and in precipitation over the northern East Asian continent with 1.5°C and 2.0°C global warming under the RCP4.5 and RCP8.5 scenarios ( [[#Miao--2020|Miao et al., 2020]] ).

Projected annual precipitation changes in the CMIP5 and CMIP6 ensembles are positive for all warming levels in ECA and TIB and for the higher warming levels in EAS. Changes in precipitation per degree Celsius global warming are larger in DJF than in JJA in ECA but show smaller seasonal difference in EAS (Figure Atlas.1 7). The EASM precipitation is projected to increase but with a complex spatial structure ( [[#Kitoh--2017|Kitoh, 2017]] ; [[#Moon--2017|Moon and Ha, 2017]] ). Simulations from CMIP5 models show that compared with the current summer climate, both SAT and precipitation increase significantly over the East Asian continent during the 1.5°C warming period (L. [[#Chen--2019|]] [[#Chen--2019|Chen et al., 2019]] ) and that the main mode of EASM precipitation changes from tripolar to dipolar ( [[#Wang--2018|Wang et al., 2018]] ). The increase in precipitable water in the wet EASM region is only slightly greater than the global average but the increase in precipitation is much greater (Z. [[#Li--2019|]] [[#Li--2019|Li et al., 2019]] ). The monsoon circulation in the lower troposphere is projected to strengthen due to the enhanced thermal forcing by the Tibetan Plateau ( [[#He--2019|He et al., 2019]] ; [[#He--2020|He and Zhou, 2020]] ), which causes the increased summer precipitation over the East Asian continent. Precipitation over eastern China increases for almost all months under global warming in projections from GCMs with different horizontal resolutions ( [[#Kusunoki--2018a|Kusunoki, 2018a]] ). Also, under RCP scenarios, in the 21st century, mean precipitation is projected to increase ( [[#Kim--2020|Kim et al., 2020]] ), especially in the late afternoons ( [[#Oh--2018|Oh and Suh, 2018]] ), over the Korean Peninsula due to global warming and associated changes in EASM. Increase in JJA mean precipitation is projected in northern East Asia consistently among the CMIP models, while northward migration of early summer East Asian rainbands such as the Meiyu-Baiu-Changma is delayed along with that of the mid-latitude westerly jet in the future ( [[#Horinouchi--2019|Horinouchi et al., 2019]] ). However, the geographical distribution of precipitation change tends to depend more on the cumulus convection scheme ( [[#Ose--2017|Ose, 2017]] ) and horizontal resolution of models rather than on SST distributions. Under the RCP4.5 and the RCP8.5 scenarios, the interannual variability in EASM rainfall is projected by the multi-model ensemble mean to increase in the 21st century ( [[#Ren--2017|Ren et al., 2017]] ). Further studies show a projected increase in heavy rainfall together with increases in rainfall intensity ( [[#Endo--2017|Endo et al., 2017]] ). Multi-model intercomparison indicates significant uncertainties in future projections of climate change in East Asia, although precipitation increases consistently across models ( [[#Zhou--2017|Zhou et al., 2017]] ). Simulations under the RCP4.5 scenario project that the number of snow days will be reduced by the end of the 21st century relative to 1986–2005, primarily owing to the decline of light snowfall events. The total amount is projected to increase in north-western China but decrease in the other sub-regions ( [[#Zhou--2018|Zhou et al., 2018]] ).

The increasing temperature trends under RCP scenarios were consistently reproduced in projections using CORDEX-EA models (Y. [[#Kim--2016|]] [[#Kim--2016|Kim et al., 2016]] ) as reported in AR5 using GCMs. However, changes in annual and seasonal mean precipitation exhibit significant inter-RCM differences with larger magnitudes and variability than in the GCMs ( [[#Ham--2016|Ham et al., 2016]] ; [[#Ozturk--2017|Ozturk et al., 2017]] ; H. [[#Sun--2018|]] [[#Sun--2018|Sun et al., 2018]] ; D. [[#Zhang--2018|]] [[#Zhang--2018|Zhang et al., 2018]] ). RCM simulations project that the Meiyu-Baiu-Changma heavy rainfall will significantly increase in northern Japan at the end of the 21st century under the RCP8.5 scenario ( [[#Osakada--2018|Osakada and Nakakita, 2018]] ), but projected precipitation amount and the number of precipitation days in summer around and over Japan differ as a result of RCM uncertainty ( [[#Suzuki-Parker--2018|Suzuki-Parker et al., 2018]] ). Annual total snowfall is projected to decrease in most parts of Japan except for Japan’s northern island under RCP2.6 ( [[#Kawase--2021|Kawase et al., 2021]] ).

Projejctions based on statistical downscaling of 37 CMIP5 GCMs for Xinjiang, China, show pronounced temperature increases of 0.27°C to 0.51°C per decade from 2021 to 2060 while precipitation changes were projected to be between –1.7% to 6.8% per decade and varying seasonally and spatially ( [[#Luo--2018|Luo et al., 2018]] ). A decrease of precipitation was projected in the western region of Xinjiang during summer. More extreme rainfall events were projected to occur during summer and autumn.

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