Editing IPCC:AR6/WGII/Chapter-10 (section)

==== 10.3.1.2 Projected Climate Change ====

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Rising temperatures increase the likelihood of the threat of heatwaves across Asia, droughts in arid and semiarid areas of West, Central and South Asia, floods in monsoon regions in South, Southeast and East Asia, and glacier melting in the HKH region ( ''high confidence'' ) ( [[#Doblas-Reyes--2021|Doblas-Reyes et al., 2021]] ; [[#Ranasinghe--2021|Ranasinghe et al., 2021]] ; [[#Seneviratne--2021|Seneviratne et al., 2021]] ). Confidence in the direction of the projected change in CIDs in Asia are summarised in Table 12.4 of WGI AR6 [[IPCC:Wg2:Chapter:Chapter-12|Chapter 12]] ( [[#Ranasinghe--2021|Ranasinghe et al., 2021]] ).

Projections of future changes in annual mean surface air temperature in Asia are qualitatively similar to those in the previous assessments with greater warming at higher latitudes (i.e., North Asia) ( ''high confidence'' ) ( [[#Gutiérrez--2021|Gutiérrez et al., 2021]] ). Projected surface air temperature changes in the Tibetan Plateau, Central Asia and West Asia are also significant ( ''high confidence'' ) ( [[#Gutiérrez--2021|Gutiérrez et al., 2021]] ). The highest levels of warming for extremely hot days are expected to occur in West and Central Asia with increased dryness of land ( ''high confidence'' ) (SR1.5). Over mountainous regions, elevation-dependent warming will continue ( ''medium confidence'' ) ( [[#Hock--2019|Hock et al., 2019]] ). Glaciers will generally shrink, but rates will vary among regions ( ''high confidence'' ) ( [[#Wester--2019|Wester et al., 2019]] ). Thawing permafrost presents a problem in northern areas of Asia, particularly Siberia ( [[#Parazoo--2018|Parazoo et al., 2018]] ). Temperature rise will be strongest in winter in most regions, while it will be the strongest on summer in the northern part of West Asia and some parts of South Asia where a desert climate prevails ( ''high confidence'' ) ( [[#Gutiérrez--2021|Gutiérrez et al., 2021]] ). The wet-bulb globe temperature, which is a measure of heat stress, is ''likely'' [[#footnote-011|2]] to approach critical health thresholds in West and South Asia under the RCP4.5 scenario, and in some other regions, such as East Asia, under the RCP8.5 scenario ( ''high confidence'' ) (Lee et al., 2021a; [[#Seneviratne--2021|Seneviratne et al., 2021]] ). The occurrence of extreme heatwaves will ''very likely'' increase in Asia. Projections show that a sizeable part of South Asia will experience heat stress conditions in the future ( ''high confidence'' ). It is ''virtually certain'' that cold days and nights will become fewer ( [[#Ranasinghe--2021|Ranasinghe et al., 2021]] ).

Projections of future annual precipitation change are qualitatively similar to those in the previous SREX and AR5 assessments ( [[#IPCC--2021|IPCC, 2021]] ). A ''very likely'' large percentage increase in annual precipitation is projected in South and North Asia ( ''high confidence'' ) ( [[#Douville--2021|Douville et al., 2021]] ; Lee et al., 2021a). Precipitation is projected to decrease over the northwest part of the Arabian Peninsula and increase over its southern part ( ''medium confidence'' ) ( [[#Gutiérrez--2021|Gutiérrez et al., 2021]] ). Both heavy and intense precipitation are projected to intensify and become more frequent in South, Southeast and East Asia ( ''high confidence'' ) ( [[#Seneviratne--2021|Seneviratne et al., 2021]] ). There will be a large increase in flood frequency in these monsoon regions ( [[#Oppenheimer--2019|Oppenheimer et al., 2019]] ). Without further mitigation efforts, this will lead to continued loss of lives and infrastructure. SR1.5 assessed higher risk from heavy precipitation events at 2°C compared with 1.5°C of global warming in East Asia. A large ensemble-modelling study shows that future warming is expected to further increase winter precipitation, and extreme weather events, such as rain-on-snow, will result in an increase in extreme runoff in Japan ( ''low confidence'' ) ( [[#Ohba--2020|Ohba and Kawase, 2020]] ). Furthermore, the earlier snowmelt will affect energy supply by hydropower.

Monsoon land precipitation ''likely'' will increase in East, Southeast and South Asia mainly due to increasing moisture convergence by elevated temperature ( ''high confidence'' ); however, there is ''low confidence'' in the magnitude and detailed spatial patterns of precipitation changes at the sub-regional scale in East Asia ( [[#Doblas-Reyes--2021|Doblas-Reyes et al., 2021]] ). Increasing land–sea thermal contrast and resultant lower tropospheric circulation changes, together with increasing moisture, are projected to intensify the South Asian summer monsoon precipitation ( ''medium confidence'' ). Anthropogenic aerosols greatly modify sub-regional precipitation changes, and their spatio-temporal changes are uncertain ( [[#Douville--2021|Douville et al., 2021]] ). Monsoonal winds will generally become weaker in a future warming world with different magnitudes across regions ( ''medium confidence'' ). Future changes in sand and dust storms are uncertain.

The global proportion of very intense TCs (category 4–5) will increase under higher levels of global warming ( ''medium to high confidence'' ). Mean global TC precipitation rate will increase ( ''medium to high confidence'' ). Models suggest a reduction in TC frequency but an increase in the proportion of very intense TCs over the western North Pacific in the future; however, some individual studies project an increase in western North Pacific TC frequency ( ''medium confidence'' ) ( [[#Cha--2020|Cha et al., 2020]] ). In the western North Pacific, some models project a poleward expansion of the latitude of maximum TC intensity, leading to a future increase in intense TC frequency south of Japan ( ''medium confidence'' ) ( [[#Yoshida--2017|Yoshida et al., 2017]] ).

Relative SLR associated with climate change in Asia will range from 0.3–0.5 m in SSP1-2.6 to 0.7–0.8 m in SSP5-8.5 for 2081–2100 relative to 1995–2014 ( [[#Ranasinghe--2021|Ranasinghe et al., 2021]] ). In coastal regions, evaluation of SLR is necessary at the regional scale to assess the impacts on coastal sectors. [[#Liu--2016c|Liu et al. (2016c)]] investigated the regional-scale SLR using dynamic downscaling from the three global-climate models in the western North Pacific. In their projection in the case following the RCP8.5 scenario, the regional sea level rises along Honshu Island in Japan during 2081–2100 relative to 1981–2000 are 6–25 cm higher than the global mean SLR due to the dynamic response of the ocean circulation. For the impact assessment of coastal hazards, the total SLR included extreme events due to storm surge and high ocean waves, which are influenced by the changes in TCs ( [[#Seneviratne--2021|Seneviratne et al., 2021]] ). [[#Mori--2016|Mori and Takemi (2016)]] summarised the characteristics of TCs in the western Pacific in the past and in the future, and the extreme value of significant wave height increased in several regions. There is considerable increase in the return levels along the China coast under 2.0°C warming compared with that under the 1.5°C warming scenario ( [[#Feng--2018b|Feng et al., 2018b]] ).

Ocean acidification will continue over the 21st century ( ''virtually certain'' ) (SROCC). Projected decrease in global surface ocean pH from 1986–2005 to 2081–2100 is about 0.145 under RCP4.5 (Lee et al., 2021a).

Diverse and complex climate characteristics in Asia limit climate models’ ability to reasonably simulate the current climate and project its future change ( [[#Gutiérrez--2021|Gutiérrez et al., 2021]] ).

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