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

==== 10.3.1.1 Observed Climate Change ====

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Observations of past and current climate in Asia are assessed in IPCC WGI AR6 ( [[#IPCC--2021|IPCC, 2021]] ). Examples of observed impacts in Asia with attributed CIDs are shown in Figure 10.2. Surface temperature has increased in the past century all over Asia ( ''very high confidence'' ). Elevation-dependent warming (i.e., the warming rate is different across elevation bands is observed in HMA) ( ''medium confidence'' ) ( [[#Hock--2019|Hock et al., 2019]] ; [[#Krishnan--2019|Krishnan et al., 2019]] ). While there is an overall trend of decreasing glacier mass in HMA, there are some regional differences and even areas with a positive mass balance due to increased precipitation ( [[#Wester--2019|Wester et al., 2019]] ). Rising temperatures have resulted in an increasing trend of growing-season length. The number of hot days and warm nights continues to increase in all of Asia ( ''high confidence'' ), while cold days and nights are decreasing except in the southern part of Siberia ( [[#Gutiérrez--2021|Gutiérrez et al., 2021]] ). Large increases in temperature extremes are observed in West and Central Asia ( ''high confidence'' ). Temperature increase is causing strong, more frequent and longer heatwaves in South and East Asia. The 2013 East China heatwaves case is such an example ( [[#Xia--2016|Xia et al., 2016]] ). In 2016 and 2018, extreme warmth was observed in Asia for which an event-attribution study revealed that this would not have been possible without anthropogenic global warming ( ''medium confidence'' ) ( [[#Imada--2018|Imada et al., 2018]] ; [[#Imada--2019|Imada et al., 2019]] ).

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[[File:24e9b419594dd459a7ab614fbea9c2e4 IPCC_AR6_WGII_Figure_10_002.png]]

'''Figure 10.2 |''' '''Detection and attribution of observed changes in Asia.''' Levels of Evidence (E), Agreement (A) and Confidence (C) are ranked by High (H), Medium (M) or Low (L). CID: climate-impact driver. References: (1) Heatwaves ( [[#Mishra--2015|Mishra et al., 2015]] ; [[#Rohini--2016|Rohini et al., 2016]] ; [[#Chen--2017|Chen and Li, 2017]] ; [[#Panda--2017|Panda et al., 2017]] ; [[#Ross--2018|Ross et al., 2018]] ); (2) Coastal urban flooding ( [[#Dulal--2019|Dulal, 2019]] ); (3) Biodiversity and habitat loss ( [[#Wan--2019|Wan et al., 2019]] ); (4) Dust storms ( [[#Kelley--2015|Kelley et al., 2015]] ; [[#Yu--2015|Yu et al., 2015]] ; [[#Alizadeh-Choobari--2016|Alizadeh-Choobari et al., 2016]] ; [[#Nabavi--2016|Nabavi et al., 2016]] ); (5) Sea level rise (only for coastal cities) ( [[#Brammer--2014|Brammer, 2014]] ; [[#Shahid--2016|Shahid et al., 2016]] ; [[#Hens--2018|Hens et al., 2018]] ); (6) Urban heat island (UHI) effect ( [[#Choi--2014|Choi et al., 2014]] ; [[#Santamouris--2015|Santamouris, 2015]] ; [[#Estoque--2017|Estoque et al., 2017]] ; [[#Ranagalage--2017|Ranagalage et al., 2017]] ; [[#Kotharkar--2018|Kotharkar et al., 2018]] ; [[#Li--2018a|Li et al., 2018a]] ; [[#Hong--2019c|Hong et al., 2019c]] ); (7) Permafrost thawing ( [[#Shiklomanov--2017a|Shiklomanov et al., 2017a]] ; [[#Biskaborn--2019|Biskaborn et al., 2019]] ); (8) Wildfire ( [[#Schaphoff--2016|Schaphoff et al., 2016]] ; [[#Brazhnik--2017|Brazhnik et al., 2017]] ); (9) Extreme rainfall events (in urban areas) ( [[#Ali--2014|Ali et al., 2014]] ); (10) Urban drought ( [[#Gu--2015|Gu et al., 2015]] ; [[#Pervin--2020|Pervin et al., 2020]] ); (11) Primary production in ocean ( [[#Roxy--2016|Roxy et al., 2016]] ); (12) Flood-induced damages ( [[#Fengqing--2005|Fengqing et al., 2005]] ); (13) Agriculture and food systems ( [[#Heino--2018|Heino et al., 2018]] ; [[#Prabnakorn--2018|Prabnakorn et al., 2018]] ).

There are considerable regional differences in observed annual precipitation trend ( ''medium confidence'' ). Observations show a decreasing trend of the South Asian summer monsoon precipitation during the second half of the 20th century ( ''high confidence'' ) ( [[#Douville--2021|Douville et al., 2021]] ). No clear trend in precipitation is observed in high-mountain Asia ( [[#Nepal--2015|Nepal and Shrestha, 2015]] ), while a continuous shift towards a drier condition has been observed since the early 1980s in spring over the central Himalaya ( [[#Panthi--2017|Panthi et al., 2017]] ). Increase in heavy precipitation occurred recently in South Asia ( ''high confidence'' ), and in Southeast and East Asia ( ''medium confidence'' ) ( [[#Seneviratne--2021|Seneviratne et al., 2021]] ). In Japan, there is no significant long-term trend in the annual precipitation, while significant increasing trend is observed in the annual number of events of heavy precipitation (daily precipitation ≥400 mm) and intense precipitation (hourly precipitation ≥50 mm) ( [[#JMA--2018|JMA, 2018]] ). Decreased precipitation and increased evapotranspiration are observed in West and Central Asia, contributing to drought conditions and decreased surface runoff.

Annual surface wind speeds have been decreasing in Asia since the 1950s ( ''high confidence'' ) ( [[#Ranasinghe--2021|Ranasinghe et al., 2021]] ). The observed changes in the frequency of sand and dust storms vary from region to region in Asia ( ''medium confidence'' ). The frequency and intensity of dust storms are increasing in some regions, such as West and Central Asia, due to land use and climate change ( [[#Mirzabaev--2019|Mirzabaev et al., 2019]] ). Significant decreasing trends of dust storms are observed in some parts of Inner Mongolia and over the Tibetan Plateau ( [[#Ranasinghe--2021|Ranasinghe et al., 2021]] ). In contrast, West Asia has witnessed more frequent and intensified dust storms affecting Iran and Persian Gulf countries in recent decades ( ''medium confidence'' ) ( [[#Nabavi--2016|Nabavi et al., 2016]] ).

There is no significant long-term trend during 1951–2017 in the numbers of tropical cyclones (TCs) with maximum winds of 66.37 km h –1 or higher forming in the western North Pacific and the South China Sea ( ''medium confidence'' ). There are substantial inter-decadal variations in basin-wide TC frequency and intensity in the western North Pacific ( [[#Lee--2020a|Lee et al., 2020a]] ). Numbers of strong TCs (maximum winds of 124.93 km h –1 or higher) also show no discernible trend since 1977 when complete wind-speed data near TC centre become available ( [[#JMA--2018|JMA, 2018]] ). According to [[#Cinco--2016|Cinco et al. (2016)]] , for TCs in the Philippines there are no significant trends in the annual number of TCs during 1951–2013. Their analysis showed that the Philippines have been affected by fewer TCs above 124.93 km h –1 , but affected more by extreme TCs (above 158.11 km h –1 ). There has been a significant northwestward shift in TC tracks since the 1980s, and a detectable poleward shift since the 1940s in the average latitude where TCs reach their peak intensity in the western North Pacific ( ''medium confidence'' ) ( [[#Lee--2020a|Lee et al., 2020a]] ).

According to [[#Bindoff--2019|Bindoff et al. (2019)]] , the oceans have warmed unabatedly since 2004, continuing the multi-decadal ocean-warming trends. Their report also summarised that there is increased agreement between coupled model simulations of anthropogenic climate change and observations of changes in ocean heat content ( ''high confidence'' ). Observed SLR around Asia over 1900–2018 is similar to the global mean sea level change of 1.7 mm yr –1 , but for the period 1993–2018, the SLR rate increased to 3.65 mm yr –1 in the Indo-Pacific region and 3.53 m yr –1 in the Northwest Pacific, compared with the global value of 3.25 mm yr –1 ( [[#Ranasinghe--2021|Ranasinghe et al., 2021]] ). The extreme SLR has occurred since the 1980s along the coast of China ( [[#Feng--2018b|Feng et al., 2018b]] ).

Ocean acidification continues with surface seawater pH values having shown a clear decrease by 0.01–0.09 from 1981–2011 along the Pacific coasts of Asia ( ''high confidence'' ) ( [[#Lauvset--2015|Lauvset et al., 2015]] ). For the western North Pacific along the 137°E line, the trend varies from −0.013 at 3°N to −0.021 at 30°N per decade during 1985–2017 ( [[#JMA--2018|JMA, 2018]] ). Ocean interior (about 150–800 m) pH also shows a decreasing trend with higher rates in the northern than the southern subtropics, which may be due to greater loading of atmospheric CO 2 in the former ( [[#JMA--2018|JMA, 2018]] ).

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