Editing IPCC:AR6/WGI/Chapter-12 (section)

=== 12.4.2 Asia ===

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According to the region definitions given in Chapter 1, Asia is divided into 11 regions: the Arabian Peninsula (ARP), Western Central Asia (WCA), West Siberia (WSB), East Siberia (ESB), the Russian Far East (RFE), East Asia (EAS), East Central Asia (ECA), the Tibetan Plateau (TIB), South Asia (SAS), South East Asia (SEA) and the Russian Arctic Region (RAR). CID changes in RAR are assessed in the Polar Region section ( [[#12.4.9|Section 12.4.9]] ). As assessed in previous IPCC Reports, major concerns in Asia are associated particularly with droughts and floods in all regions, heat extremes in SAS and EAS, sand-dust storms in WCA, tropical cyclones in SEA and EAS, snow cover and glacier changes in ECA and the Hindu Kush Himalaya (HKH) region, and sea ice and permafrost thawing in northern Asia.

Since AR5, a large body of new literature is now available relevant to climate change in Asia, which includes projections of both mean climate and extreme climate phenomena from global and regional ensembles of climate simulations such as CMIP6 and CORDEX ( [[IPCC:Wg1:Chapter:Chapter-10|Chapter 10]] and the Atlas). Literature has also considerably grown on several climate topics relevant to Asia such as the mountain climate ( [[IPCC:Wg1:Chapter:Chapter-3|Chapter 3]] of the SROCC), and the novel regional assessments such as the Hindu Kush Himalaya Assessment ( [[#Wester--2019|Wester et al., 2019]] ). Figure 12.6 shows the regional changes in indices related to floods, and coastal erosion over Asia, which are assessed on a regional basis along with other climatic impact-driver indices below.

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[[File:ceaaf766f0a386cf4d807136bb2b937f IPCC_AR6_WGI_Figure_12_6.png]]

'''Figure 12.6''' '''|''' '''Projected changes in selected climatic impact-driver indices for Asia.''' '''(a)''' Mean change in 1-in-100-year river discharge per unit catchment area (Q100, m <sup>3</sup> s <sup>–1</sup> km <sup>–2</sup> ) from CORDEX models for the West, South East and East Asia domains for 2041–2060 relative to 1995–2014 for RCP8.5. '''(b)''' Shoreline position change along sandy coasts by the year 2100 relative to 2010 for RCP8.5 (metres; negative values indicate shoreline retreat) from the CMIP5-based dataset presented by [[#Vousdoukas--2020b|Vousdoukas et al. (2020b)]] . '''(c)''' Bar plots for Q100 (m <sup>3</sup> s <sup>–1</sup> km <sup>–2</sup> ) averaged over land areas for the AR6 WGI Reference Regions (defined in Chapter 1). The left-hand column within each panel (associated with the left-hand y-axis) shows the ‘recent past’ (1995–2014) Q100 absolute values in grey shades. The other columns (associated with the right-hand y-axis) show the Q100 changes relative to the recent past values for two time periods (‘mid’ 2041–2060 and ‘long’ 2081–2100) and for three global warming levels (defined relative to the pre-industrial period 1850–1900): 1.5°C (purple), 2°C (yellow) and 4°C (brown). The bars show the median (dots) and the 10–90th percentile range of model ensemble values across each model ensemble. CMIP6 is shown by the darkest colours, CMIP5 by medium, and CORDEX by light. SSP5-8.5/RCP8.5 is shown in red and SSP1-2.6/RCP2.6 in blue. '''(d)''' Bar plots for shoreline position change show CMIP5-based projections of shoreline position change along sandy coasts for 2050 and 2100 relative to 2010 for RCP8.5 (red) and RCP4.5 (blue) from [[#Vousdoukas--2020b|Vousdoukas et al. (2020b)]] . Dots indicate regional mean change estimates and bars show the 5–95th percentile range of associated uncertainty. Note that these shoreline position change projections assume that there are no additional sediment sinks/sources or any physical barriers to shoreline retreat. See Technical ( [[IPCC:Wg1:Chapter:Annex-vi|Annex VI]] for details of indices. Further details on data sources and processing are available in the chapter data table (Table 12.SM.1).

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==== 12.4.2.1 Heat and Cold ====

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'''Mean air temperature:''' A long-term warming trend in annual mean surface temperature has been observed across Asia during 1960–2015, and the warming accelerated after the 1970s ( ''high confidence'' ) ( [[#Davi--2015|Davi et al., 2015]] ; [[#Aich--2017|Aich et al., 2017]] ; [[#Cheong--2018|Cheong et al., 2018]] ; S. [[#Dong--2018|]] [[#Dong--2018|Dong et al., 2018]] ; [[#IPCC--2018|IPCC, 2018]] ; [[#Krishnan--2019|Krishnan et al., 2019]] ; M. [[#Zhang--2019|]] [[#Zhang--2019|]] [[#Zhang--2019|]] [[#Zhang--2019|Zhang et al., 2019]] ). Records also indicate a higher rate of warming in minimum temperatures than maximum temperatures in Asia, leading to more frequent warm nights and warm days, and less frequent cold days and cold nights ( ''high confidence'' ) ( [[#Supari--2017|Supari et al., 2017]] ; [[#Akperov--2018|Akperov et al., 2018]] ; [[#Cheong--2018|Cheong et al., 2018]] ; [[#Rahimi--2018|Rahimi et al., 2018]] ; [[#Khan--2019a|Khan et al., 2019a]] ; L. [[#Li--2019|]] [[#Li--2019|Li et al., 2019]] ; M. [[#Zhang--2019|]] [[#Zhang--2019|]] [[#Zhang--2019|]] [[#Zhang--2019|Zhang et al., 2019]] ).

Projections show continued warming over Asia in the future with contrasted regional patterns across the continent ( ''high confidence'' ) (Figure 4.19). For RCP8.5/SSP5-8.5 at the end of the century, the mean estimated warming exceeds 5°C in WSB, ESB and RFE and 7°C in some parts ( ''high confidence'' ). In most areas of ARP and WCA, 5°C is exceeded ( [[#Ozturk--2017|Ozturk et al., 2017]] ), but EAS, SAS and SEA have a lower projected warming of less than 5°C ( [[#Basha--2017|Basha et al., 2017]] ; [[#Lu--2019|]] [[#Lu--2019|C. Lu et al., 2019]] ; [[#Almazroui--2020|Almazroui et al., 2020]] ; Atlas.5). Under SSP1-2.6, the warming remains limited to 2°C in most areas except Arctic regions, where it exceeds 2°C (Figure 4.19).

'''Extreme heat:''' There is increased evidence and ''high confidence'' of more frequent heat extremes in the recent decades than in previous ones in most of Asia ( [[#Acar%20Deniz--2015|Acar Deniz and Gönençgil, 2015]] ; [[#Rohini--2016|Rohini et al., 2016]] ; [[#Mishra--2017|Mishra et al., 2017]] ; [[#You--2017|You et al., 2017]] ; [[#Imada--2018|Imada et al., 2018]] ; [[#Khan--2019b|Khan et al., 2019b]] ; [[#Krishnan--2019|Krishnan et al., 2019]] ; [[#Rahimi--2019|Rahimi et al., 2019]] ; [[#Yin--2019|Yin et al., 2019]] ; Chapter 11) due to the effects of anthropogenic global warming, El Niño and urbanization ( [[#Luo--2017|Luo and Lau, 2017]] ; [[#Thirumalai--2017|Thirumalai et al., 2017]] ; [[#Imada--2019|Imada et al., 2019]] ; Y. [[#Sun--2019|]] [[#Sun--2019|]] [[#Sun--2019|Sun et al., 2019]] ; [[#Zhou--2019|Zhou et al., 2019]] ). But there is ''medium confidence'' of heat extremes increasing in frequency in many parts of India ( [[#Rohini--2016|Rohini et al., 2016]] ; [[#Mazdiyasni--2017|Mazdiyasni et al., 2017]] ; [[#van%20Oldenborgh--2018|van Oldenborgh et al., 2018]] ; [[#Sen%20Roy--2019|Sen Roy, 2019]] ; [[#Kumar--2020|Kumar et al., 2020]] ) partly due to the alleviation of anthropogenic warming by increased air pollution with aerosols and expanding irrigation ( [[#van%20Oldenborgh--2018|van Oldenborgh et al., 2018]] ; [[#Thiery--2020|Thiery et al., 2020]] ).

Extreme heat events are ''very likely'' to become more intense and/or more frequent in SAS, WCA, ARP, EAS, and SEA by the end of 21st century, especially under RCP6.0 and RCP8.5 (Figure 12.4a–c and Chapter 11; [[#Lelieveld--2016|Lelieveld et al., 2016]] ; [[#Pal--2016|Pal and Eltahir, 2016]] ; [[#Guo--2017|Guo et al., 2017]] ; [[#Mishra--2017|Mishra et al., 2017]] ; [[#Dosio--2018|Dosio et al., 2018]] ; [[#Lin--2018|Lin et al., 2018]] ; [[#Nasim--2018|Nasim et al., 2018]] ; [[#Shin--2018|Shin et al., 2018]] ; [[#Hong--2019|Hong et al., 2019]] ; [[#Su--2019|Su and Dong, 2019]] ; [[#Khan--2020|Khan et al., 2020]] ; [[#Kumar--2020|Kumar et al., 2020]] ). The exceedance of the dangerous heat stress 41°C threshold of the HI is expected to increase by about 250 days in SEA and by 50–150 days in SAS, WCA, ARP and EAS for SSP5-8.5 at the end of the century (Figure 12.4d–f and Figure 12.SM.2). Under SSP1-2.6, the increase would be restricted to less than 30 days in many of these regions except SEA, where the number of exceedance days increases by about 100 days in some areas. Such increases are already present in the middle of the century (Figure 12.4d–f; [[#Schwingshackl--2021|Schwingshackl et al., 2021]] ). In these regions, the increase in number of days with exceedance of 35°C of high heat stress is also expected to increase substantially for the mid-century under SSP5-8.5 (typically by 10–50 days except in Arctic and Siberian regions), and by more than 60 days in areas of SEA, and a large difference is found between low- and high-end scenarios in the end of the century ( ''high confidence'' ) (Figure 12.4b). Over WSB, ESB and RFE also, an increase of extreme heat durations and frequency is expected in all scenarios ( ''high confidence'' ) ( [[#Kattsov--2017|Kattsov et al., 2017]] ; [[#Khlebnikova--2019b|Khlebnikova et al., 2019b]] ).

'''Cold spell and frost:''' Cold spells intensity and frequency, as well as the number of frost days, in most Asian regions have been decreasing since the beginning of the 20th century ( ''high confidence'' ) (Chapter 11; [[#Sheikh--2015|Sheikh et al., 2015]] ; [[#Donat--2016|Donat et al., 2016]] ; [[#Erlat--2016|Erlat and Türkeş, 2016]] ; S. [[#Dong--2018|]] [[#Dong--2018|Dong et al., 2018]] ; [[#Liao--2018|Liao et al., 2018]] , 2020; [[#Lu--2018|Lu et al., 2018]] ; [[#van%20Oldenborgh--2019|van Oldenborgh et al., 2019]] ), except for the central Eurasian regions, where there was a cooling trend during 1995–2014, which is linked to sea ice loss in the Barents–Kara Seas ( ''medium confidence'' ) (Atlas.5.2; [[#Wegmann--2018|Wegmann et al., 2018]] ; [[#Blackport--2019|Blackport et al., 2019]] ; [[#Mori--2019|Mori et al., 2019]] ).

It is ''very likely'' that cold spells will have a decreasing frequency in all future scenarios across Asian regions (J. [[#Guo--2018|]] [[#Guo--2018|Guo et al., 2018]] ; [[#Sui--2018|Sui et al., 2018]] ; L. [[#Li--2019|]] [[#Li--2019|Li et al., 2019]] ), as well as frost days (L. [[#Wang--2017|]] [[#Wang--2017|]] [[#Wang--2017|Wang et al., 2017]] ; [[#Fallah-Ghalhari--2019|Fallah-Ghalhari et al., 2019]] ) except in tropical Asia (Chapter 11).

'''In Asia, temperatures have warmed during the last century''' ( high confidence '''). Extreme heat episodes have become more frequent in most regions''' ( high confidence '''), and are''' very likely '''to increase in all regions of Asia under all warming scenarios during this century. Dangerous heat stress thresholds such as HI &gt; 41°C will be crossed much more often (typically 5''' '''0–1''' '''50 days per year more than the recent past) in many southern Asia regions at the end of the century under SSP5-8.5 while these numbers should remain limited to a few tens under SSP1-2.6''' ( high confidence '''). It is''' very likely '''that cold spells and frost days will decrease in frequency in all future scenarios across Asian regions during the century.'''

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==== 12.4.2.2 Wet and Dry ====

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'''Mean precipitation:''' The most prominent features about changes in precipitation over Asia (1901–2010) are the increasing precipitation trends across higher latitudes, along with some scattered smaller regions of detectable increases and decreases ( [[#Knutson--2018|Knutson and Zeng, 2018]] ); however, spatial variability remains high (W. [[#Wang--2015|]] [[#Wang--2015|Wang et al., 2015]] ; [[#Limsakul--2016|Limsakul and Singhruck, 2016]] ; [[#Supari--2017|Supari et al., 2017]] ; [[#Rahimi--2018|Rahimi et al., 2018]] , 2019; [[#Sein--2018|Sein et al., 2018]] ; [[#Kumar--2019|Kumar et al., 2019]] ; H. [[#Wang--2019|]] [[#Wang--2019|]] [[#Wang--2019|]] [[#Wang--2019|Wang et al., 2019]] ; see Atlas.5) ( ''medium confidence'' ).

Mean precipitation is ''likely'' to increase in most areas of northern (WSB, ESB, RFE), southern (ECA, TIB, SAS) and East Asia (EAS) in different scenarios ( ''high confidence'' ) ( [[#Huang--2014|Huang et al., 2014]] ; [[#Xu--2017|Xu et al., 2017]] ; [[#Kusunoki--2018|Kusunoki, 2018]] ; [[#Mandapaka--2018|Mandapaka and Lo, 2018]] ; [[#Luo--2019|Luo et al., 2019]] ; [[#Wu--2019|Wu et al., 2019]] ; X. [[#Zhu--2019|]] [[#Zhu--2019|Zhu et al., 2019]] ; [[#Almazroui--2020|Almazroui et al., 2020]] ; [[#Jiang--2020|Jiang et al., 2020]] ; [[#Rai--2020|Rai et al., 2020]] ; see Atlas.5). Monsoon circulation will also increase seasonal contrasts, with SAS seeing wetter wet seasons and drier dry seasons (Atlas.5.3). Higher uncertainty between CMIP5 and CMIP6 as well as spatial differences lend ''low confidence'' to model projections in ARP and WCA (Atlas.5.5), with large seasonal differences ( [[#Zhu--2020|Zhu et al., 2020]] ) and some models projecting decreases in precipitation in Central Asia ( [[#Ozturk--2017|Ozturk et al., 2017]] ), Pakistan ( [[#Nabeel--2020|Nabeel and Athar, 2020]] ) and SEA (Supari et al., 2020).

'''River flood:''' Flood risk has grown in many places in China from 1961 to 2017 ( [[#Kundzewicz--2019|Kundzewicz et al., 2019]] ) ( ''low confidence'' ). In SAS, the numbers of flood events and human fatalities have increased in India during 1978–2006 ( [[#Singh--2013|Singh and Kumar, 2013]] ), whereas the average country-wide inundation depth has been decreasing during 2002–2010 in Bangladesh, attributed to improved flood management ( ''low confidence'' ) ( [[#Sciance--2018|Sciance and Nooner, 2018]] ).

Given the increase of heavy precipitation in most Asian regions, the river flood frequency and intensities will change consequently in Asia. Over China floods will increase with different levels under different warming scenarios ( ''medium confidence'' ) ( [[#Lin--2018|Lin et al., 2018]] ; [[#Kundzewicz--2019|Kundzewicz et al., 2019]] ; [[#Liang--2019|Liang et al., 2019]] ; [[#Gu--2020|Gu et al., 2020]] ). Monsoon floods will be more intense in SAS ( ''medium confidence'' ) ( [[#Nowreen--2015|Nowreen et al., 2015]] ; [[#Babur--2016|Babur et al., 2016]] ; [[#Mohammed--2018|Mohammed et al., 2018]] ). The total flood damage will increase greatly in river basins in SEA countries under the conditions of climate change and rapid urbanization in the near future ( [[#Dahal--2018|Dahal et al., 2018]] ; [[#Kefi--2020|Kefi et al., 2020]] ). A changing snowmelt regime in the mountains may contribute to a shift of spring floods to earlier periods in Central Asia in future ( ''medium confidence'' ) ( [[#Reyer--2017b|Reyer et al., 2017b]] ). The annual maximum river discharge can almost double by the mid-21st century in major Siberian rivers, and annual maximum flood area is projected to increase across Siberia mostly by 2–5% relative to the baseline period (1990–1999) under RCP8.5 scenario ( ''medium confidence'' ) ( [[#Shkolnik--2018|Shkolnik et al., 2018]] ).

'''Heavy precipitation and pluvial flood:''' Pluvial floods are driven by extreme precipitation and land use. Observed changes in extreme precipitation vary considerably by region (Chapter 11). Heavy precipitation is ''very'' ''likely'' to become more intense and frequent in all areas of Asia except in ARP ( ''medium confidence'' ) for a 2°C GWL or higher (Chapter 11).

'''Landslide:''' The majority of non-seismic fatal landslide events were triggered by rainfall, and Asia is the dominant geographical area of landslide distribution ( [[#Froude--2018|Froude and Petley, 2018]] ). Floods and landslides are the most frequently occurring natural hazards in the eastern Himalayas and hilly regions, particularly caused by torrential rain during the monsoon season ( [[#Gaire--2015|Gaire et al., 2015]] ; [[#Syed--2016|Syed and Al Amin, 2016]] ). They accounted for nearly half of the events recorded in the countries of the HKH region ( [[#Vaidya--2019|Vaidya et al., 2019]] ). Intense monsoon rainfall in northern India and western Nepal in 2013, which led to landslides and one of the worst floods in history, has been linked to increased loading of GHG and aerosols ( [[#Cho--2016|Cho et al., 2016]] ). Due to an increase of heavy precipitation and permafrost thawing, an increase in landslides is expected in some areas of Asia, such as northern Taiwan (China), some South Korean mountains, Himalayan mountains, and permafrost territories of Siberia, and the increase is expected to be the greatest over areas covered by current glaciers and glacial lakes ( ''medium confidence'' , ''medium evidence'' ) ( [[#Kim--2015|Kim et al., 2015]] ; [[#Kharuk--2016|Kharuk et al., 2016]] ; C.-W. [[#Chen--2019|]] [[#Chen--2019|Chen et al., 2019]] ; [[#Kirschbaum--2020|Kirschbaum et al., 2020]] ).

'''Aridity:''' Aridity in West Central Asia and parts of South Asia increased in recent decades ( ''medium confidence'' ), as documented in Afghanistan ( [[#Qutbudin--2019|Qutbudin et al., 2019]] ), Iran ( [[#Zarei--2016|Zarei et al., 2016]] ; [[#Zolfaghari--2016|Zolfaghari et al., 2016]] ; [[#Pour--2020|Pour et al., 2020]] ), most parts of Pakistan (K. [[#Ahmed--2018|Ahmed et al., 2018]] , 2019), and many parts of India ( [[#Roxy--2015|Roxy et al., 2015]] ; [[#Mallya--2016|Mallya et al., 2016]] ; [[#Matin--2017|Matin and Behera, 2017]] ; [[#Ramarao--2019|Ramarao et al., 2019]] ). Some spatial and seasonal differences within these regions remain, with [[#Ambika--2020|Ambika and]] [[#Mishra--2020|Mishra (2020)]] noting significant aridity declines over the Indo–Gangetic Plain in India during 1979–2018 due in part to the effect of irrigation, and [[#Araghi--2018|Araghi et al. (2018)]] found that many parts of Iran show no significant trends in aridity. There was a drying tendency in the dry season and significant wetting in the wet season in the Philippines during 1951–2010 ( [[#Villafuerte--2014|Villafuerte et al., 2014]] ), and slight wetting in Vietnam during 1980–2017 ( [[#Stojanovic--2020|Stojanovic et al., 2020]] ) ( ''low confidence'' ). In EAS there is ''low confidence'' of broad aridity changes, as the frequency of droughts have increased (especially in spring) along a strip extending from south-west China to the western part of north-east China; however, there is no evidence of a significant increase in drought severity over China as a whole and many parts in the arid north-west China got wetter during 1961–2012 (W. [[#Wang--2015|]] [[#Wang--2015|Wang et al., 2015]] ; [[#Zhai--2017|Zhai et al., 2017]] ; H. [[#Wang--2019|]] [[#Wang--2019|]] [[#Wang--2019|]] [[#Wang--2019|Wang et al., 2019]] ; [[#Zhang--2019|Zhang and Shen, 2019]] ). In Siberia, the number of dry days has decreased for much of the region, but increased in its southern parts ( [[#Khlebnikova--2019a|Khlebnikova et al., 2019a]] ).

The counteracting factors of projected increases in precipitation and temperature across most of Asia ( [[IPCC:Wg1:Chapter:Chapter-11#11.9|Section 11.9]] and Atlas.5) leads to ''low confidence'' ( ''limited evidence'' , inconsistent trends) for broad, long-term aridity changes with ''medium confidence'' only for aridity increases in West Central Asia and East Asia. A growing number of studies highlight the potential for more localized aridity trends, including projection ensembles indicating significant increase in aridity and more frequent and intense droughts in most parts of China (Y. [[#Li--2019|]] [[#Li--2019|Li et al., 2019]] ; [[#Yao--2020|Yao et al., 2020]] ) and India under RCP4.5 and RCP8.5 for the 2020–2100 period ( [[#Gupta--2018|Gupta and Jain, 2018]] ; [[#Bisht--2019|Bisht et al., 2019]] ; [[#Preethi--2019|Preethi et al., 2019]] ).

'''Hydrological drought:''' Section 11.9 indicates that ''limited evidence'' and inconsistent regional trends gives ''low confidence'' to observed and projected changes in hydrological drought in all Asian regions at a 2°C GWL (approximately mid-century), although West Central Asia hydrological droughts increase at the 4°C GWL (approximately end-of-century under higher emissions scenarios) ( ''medium confidence'' ). Human activities such as reservoir operation and water abstraction have had a profound effect on low river flow characteristics and drought impacts in many Asian regions ( [[#Kazemzadeh--2016|Kazemzadeh and Malekian, 2016]] ; [[#Yang--2020b|Yang et al., 2020b]] ). There was no observed overall long-term change of both meteorological droughts and hydrological droughts over India during 1870–2018 ( [[#Mishra--2020|Mishra, 2020]] ), but there were strong trends towards drying of soil moisture in north-central India ( [[#Ganeshi--2020|Ganeshi et al., 2020]] ) and intensified droughts in north-west India, parts of Peninsular India, and Myanmar ( [[#Malik--2016|Malik et al., 2016]] ). The frequency of water scarcity connected with hydrological droughts has increased significantly in southern Russia since the beginning of the 21st century ( [[#Frolova--2017|Frolova et al., 2017]] ). Higher future temperatures are expected to alter the seasonal profile of hydrologic droughts given reduced summer snowmelt ( ''medium confidence'' ) downstream of mountains such as the Himalayas and the Tibetan Plateau ( [[#Sorg--2014|Sorg et al., 2014]] ). Several studies project more severe future hydrological drought in the Weihe River basin in northern China ( [[#Yuan--2016|Yuan et al., 2016]] ; [[#Sun--2020|Sun and Zhou, 2020]] ).

'''Agricultural and ecological drought:''' Section 11.9 assesses ''medium confidence'' in observed increases to agricultural and ecological droughts in West Central Asia, East Central Asia, and East Asia. Persistent droughts were the main factor for grassland degradation and desertification in Central Asia in the early 21st century (G. [[#Zhang--2018|]] [[#Zhang--2018|Zhang et al., 2018]] ; [[#Emadodin--2019|Emadodin et al., 2019]] ). Compound meteorological drought and heat events, which lead to water stress conditions for agricultural and ecological systems, have become more frequent, widespread and persistent in China especially since the late 1990s ( [[#Yu--2020|Yu and Zhai, 2020]] ). There were more agricultural droughts in northern China than in southern China, and the intensity of agricultural drought increased during 1951–2018 ( [[#Zhao--2021|Zhao et al., 2021]] ).

Studies examining a 2°C GWL give ''low confidence'' for projected broad changes to agricultural and ecological drought across all Asia regions, although at 4°C GWL agricultural and ecological drought increases are projected for West Central Asia and East Asia along with a decrease in South Asia ( ''medium confidence'' ) ( [[IPCC:Wg1:Chapter:Chapter-11#11.9|Section 11.9]] ). Summer temperature increase will enhance evapotranspiration, facilitating ecological and agricultural drought over Central Asia towards the latter half of this century (Chapter 11; see also Figure 12.4 for soil moisture and DF indices; [[#Ozturk--2017|Ozturk et al., 2017]] ; [[#Reyer--2017b|Reyer et al., 2017b]] ; [[#Senatore--2019|Senatore et al., 2019]] ). However, broader changes in droughts could not be determined in Asia due to the mixture of total precipitation signals together with temperature increase patterns ( [[IPCC:Wg1:Chapter:Chapter-11#11.9|Section 11.9]] and Atlas.5).

'''Fire weather:''' Under the global warming scenario of 2°C, the magnitude of length and frequency of fire seasons are projected to increase with strong effects in India, China and Russia ( ''medium confidence'' ) (Q. [[#Sun--2019|]] [[#Sun--2019|]] [[#Sun--2019|Sun et al., 2019]] ). [[#Abatzoglou--2019|Abatzoglou et al. (2019)]] found that higher fire weather conditions due to climate change emerge in the first part of the 21st century in South China, WCA as well as in boreal areas of Siberia and RFE. The potential burned areas in five Central Asian countries (Kazakhstan, Kyrgyzstan, Tajikistan, Uzbekistan and Turkmenistan) will increase by 2–8% in the 2030s and 3–13% in the 2080s compared with the baseline ( ''medium confidence'' ) (1971–2000; [[#Zong--2020|Zong et al., 2020]] ).

'''In conclusion, there is''' medium confidence '''that extreme precipitation, mean precipitation and river floods will increase across most Asian regions. There is''' low confidence '''for projected changes in aridity and drought given overall increases in precipitation and regional inconsistencies, with medium increases for West Central Asia and East Asia especially beyond the middle of the century and global warming levels beyond 2°C. Fire weather seasons are projected to lengthen and intensify particularly in the northern regions''' ( medium confidence ''').'''

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==== 12.4.2.3 Wind ====

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'''Mean wind speed:''' There is ''high confidence'' of the slowdown in terrestrial near-surface wind speed (SWS) in Asia by approximately –0.1 m s <sup>–1</sup> per decade since the 1950s based on observations and reanalysis data, with the significant decreases in Central Asia among the highest in the world followed by EAS and SAS (J. [[#Wu--2018|]] [[#Wu--2018|Wu et al., 2018]] ; [[#Tian--2019|Tian et al., 2019]] ; R. [[#Zhang--2019|]] [[#Zhang--2019|]] [[#Zhang--2019|]] [[#Zhang--2019|Zhang et al., 2019]] ). But a short-term strengthening in SWS was observed during the winter since 2000 in eastern China ( ''medium confidence'' ) ( [[#Zeng--2019|Zeng et al., 2019]] ; [[#Zha--2019|Zha et al., 2019]] ).

There is ''medium confidence'' of future declining mean SWS in Asia, except in SAS and SEA, as global projections indicate a decreasing trend in all climate scenarios for most of northern Asia, TIB and East Asia by the mid-century ( [[#Karnauskas--2018a|Karnauskas et al., 2018a]] ; [[#Fedotova--2019|Fedotova, 2019]] ; [[#Jung--2019|Jung and Schindler, 2019]] ; [[#Ohba--2019|Ohba, 2019]] ; J. [[#Wu--2020|]] [[#Wu--2020|Wu et al., 2020]] ; [[#Zha--2020|Zha et al., 2020]] ; Figure 12.4m–o), with negative effects on wind energy potential. Decreases in North Asia are generally modest, not exceeding 10% for the mid-century and 20% for the end of century for the RCP8.5 and RCP4.5 scenarios (Figure 12.4m–o).

'''Severe wind storms:''' Consistent with the general mean decreasing surface winds, there is ''medium confidence'' that strong winds declined faster than weak winds in the past few decades in Asia in general ( [[#Vautard--2010|Vautard et al., 2010]] ; [[#Tian--2019|Tian et al., 2019]] ), but evidence is lacking for spatial patterns. There is ''low confidence'' that extra-tropical cyclones will decline in number in future climate scenarios over WCA, TIB, WSB and ESB, and intensify over the Arctic regions as a result of the poleward shift of storm tracks ( [[#Basu--2018|Basu et al., 2018]] ; Chapter 11). There is ''limited evidence'' for projection of changes in severe winds occurring in convective storms in Asia.

'''Tropical cyclone:''' There was an increase in the number and intensification rate of intense tropical cyclones (TC), such as Category 4–5 (wind speeds &gt;58 m s <sup>–1</sup> ), in the Western North Pacific (WNP) and Bay of Bengal since the mid-1980s ( ''medium confidence'' ) ( [[IPCC:Wg1:Chapter:Chapter-11#11.7|Section 11.7]] ; [[#Kim--2016|Kim et al., 2016]] ; [[#Mei--2016|Mei and Xie, 2016]] ; [[#Walsh--2016a|Walsh et al., 2016a]] ; [[#Knutson--2019|Knutson et al., 2019]] ). There is ''medium confidence'' that there has been a significant north-westward shift in TC tracks and a poleward shift in the average latitude where TCs reach their peak intensity in the WNP since the 1980s ( [[#Knutson--2019|Knutson et al., 2019]] ; J. [[#Sun--2019|]] [[#Sun--2019|]] [[#Sun--2019|Sun et al., 2019]] ; [[#Lee--2020|Lee et al., 2020]] ), increasing exposure to TC passage and more destructive landfall over eastern China, Japan, and Korea in the last few decades ( [[#Kossin--2016|Kossin et al., 2016]] ; [[#Li--2017|Li et al., 2017]] ; [[#Altman--2018|Altman et al., 2018]] ; [[#Liu--2019|Liu and Chan, 2019]] ), and decreasing exposure in the region of SAS and southern China ( [[#Cinco--2016|Cinco et al., 2016]] ; [[#Kossin--2016|Kossin et al., 2016]] ; see Chapter 11). However, while the analysis shows fewer typhoons, more extreme TCs have affected the Philippines ( ''low confidence'' ) ( [[#Takagi--2016|Takagi and Esteban, 2016]] ). The frequency and duration of tropical cyclones has significantly increased over time over the Arabian Sea and insignificantly decreased over the Bay of Bengal during 1977–2018 ( ''low confidence'' ) ( [[#Fan--2020|Fan et al., 2020]] ).

There is ''medium confidence'' that future TC numbers will decrease but the maximum TC wind intensities will increase in the western Pacific as elsewhere (Chapter 11, see Figure 11.24; [[#Choi--2019|Choi et al., 2019]] ; [[#Cha--2020|Cha et al., 2020]] ; [[#Knutson--2020|Knutson et al., 2020]] ). The simulations for the late 21st century for the RCP8.5 scenario yield considerably more TCs in the WNP that exceed 49.4 m s <sup>−1</sup> (Category 3) intensity ( [[#Mclay--2019|Mclay et al., 2019]] ). There is ''medium confidence'' that the average location of the maximum wind will migrate poleward (see Chapter 11), and TC translation speeds at the higher latitudes would decrease ( [[#Yamaguchi--2020|Yamaguchi et al., 2020]] ). As a consequence, the intensity of TCs affecting the Japan Islands would increase in the future under the RCP8.5 scenario ( [[#Yoshida--2017|Yoshida et al., 2017]] ), whereas the frequency of TCs affecting the Philippine region and Vietnam is projected to decrease ( [[#Kieu-Thi--2016|Kieu-Thi et al., 2016]] ; [[#Wang--2017|]] [[#Wang--2017|]] [[#Wang--2017|C. Wang et al., 2017]] ; [[#Gallo--2019|Gallo et al., 2019]] ) ( ''medium confidence'' ).

'''Sand and dust storm''' : The Asia-Pacific region contributes 26.8 per cent to global dust emissions as of 2012 ( [[#UNESCAP--2018|UNESCAP, 2018]] ). In West Asia, the frequency of dust events has increased markedly in some areas (east and north-east of Saudi Arabia, north-west of Iraq and east of Syria) from 1980 to the present ( [[#Nabavi--2016|Nabavi et al., 2016]] ; [[#Alobaidi--2017|Alobaidi et al., 2017]] ). This marked dust increase has been associated with drought conditions in the Fertile Crescent ( [[#Notaro--2015|Notaro et al., 2015]] ; [[#Yu--2015|Yu et al., 2015]] ), ''likely'' amplified by anthropogenic warming ( [[#Kelley--2015|Kelley et al., 2015]] ; Chapter 10). Dust storm frequency in most regions of northern China show a decreasing trend since the 1960s due to the decrease in surface wind speed ( ''medium confidence'' ) ( [[#Guan--2017|Guan et al., 2017]] ).

While dust activity has decreased greatly over EAS, current climate models are unable to reproduce the trends ( [[#Guan--2015|Guan et al., 2015]] , 2017; [[#Zha--2017|Zha et al., 2017]] ; [[#Wu--2018|]] [[#Wu--2018|C. Wu et al., 2018]] ). Thus, there is ''limited evidence'' for future trends of sand and dust storms in Asia.

'''In conclusion, surface wind speeds have been decreasing in Asia''' ( high confidence '''), but there is a large uncertainty in future trends. There is''' medium confidence '''that mean wind speeds will decrease in Central and northern Asia, and that tropical cyclones will have decreasing frequency and increasing intensity overall.'''

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<span id="snow-and-ice-2"></span>
==== 12.4.2.4 Snow and Ice ====

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'''Snow:''' There is no significant interannual trend of total snow cover from 2000 to 2016 over Eurasia (X. [[#Wang--2017|]] [[#Wang--2017|]] [[#Wang--2017|Wang et al., 2017]] a; [[#Sun--2020|Sun et al., 2020]] ). Observations do show significant changes in the seasonal timing of Eurasian snow cover extent (especially for earlier spring snowmelt) since the 1970s, with seasonal changes expected to continue in the future ( ''high confidence'' ) ( [[#Yeo--2017|Yeo et al., 2017]] ; [[#Zhong--2021|Zhong et al., 2021]] ). By 2100, snowline elevations are projected to rise between 400 and 900 m (4.4 to 10.0 m yr <sup>–1</sup> ) in the Indus, Ganges and Brahmaputra basins under the RCP8.5 scenario ( [[#Viste--2015|Viste and Sorteberg, 2015]] ).

'''Glacier:''' Observation and future projection of glacier mass changes in Asia are assessed in [[IPCC:Wg1:Chapter:Chapter-9#9.5.1|Section 9.5.1]] grouped in three main regions: northern Asia, High Mountains of Asia, and Caucuses and Middle East. All regions show continuing decline in glacier mass and area in the coming century ( ''high confidence'' ). Under RCP2.6 the pace of glacier loss slows, but glacier losses increase in RCP8.5 and peak in the mid to late 21st century. GlacierMIP projections indicate that glaciers in the High Mountains of Asia lose 42 ± 25%, 56 ± 24% and 71 ± 21% of their 2015 mass by the end of the century for RCP2.6, RCP4.5 and RCP8.5 scenarios respectively. Under the same scenarios, glaciers in North Asia would lose 57 ± 40%, 72 ± 38% and 85 ± 30% of their mass, and glaciers in the Caucuses and the Middle East would lose 68 ± 32%, 83 ± 19% and 94 ± 13% of their mass (see also [[#Kraaijenbrink--2017|Kraaijenbrink et al., 2017]] ; [[#Rounce--2020|Rounce et al., 2020]] ).

Although enhanced meltwater from snow and glaciers largely offsets hydrological drought-like conditions ( [[#Pritchard--2019|Pritchard, 2019]] ), this effect is unsustainable and may reverse as these cryospheric buffers disappear ( ''medium confidence'' ) ( [[#Gan--2015|Gan et al., 2015]] ; W. [[#Dong--2018|]] [[#Dong--2018|Dong et al., 2018]] ; [[#Huss--2018|Huss and Hock, 2018]] ). In the Himalayas and the TIB region higher temperatures will lead to higher glacier melt rates and significant glacier shrinkage and a summer runoff decrease ( ''medium confidence'' ) ( [[#Sorg--2014|Sorg et al., 2014]] ). Glacier runoff in the Asian high mountains will increase up to mid-century, and after that runoff might decrease due to the loss of glacier storage ( ''medium confidence'' ) ( [[#Lutz--2014|Lutz et al., 2014]] ; [[#Huss--2018|Huss and Hock, 2018]] ; [[#Rounce--2020|Rounce et al., 2020]] ).

Compared with the 1990s, the number of lakes in TIB in the 2010s decreased by 2%, whereas total lake area expanded by 25% (S. [[#Wang--2020|]] [[#Wang--2020|Wang et al., 2020]] ) due to the joint effect of precipitation increase and glacier retreat. Many new lakes are predicted to form as a consequence of continued glacier retreat in the Himalaya-Karakoram region ( [[#Linsbauer--2016|Linsbauer et al., 2016]] ). As many of these lakes will develop at the immediate foot of steep icy peaks with degrading permafrost and decreasing slope stability, the risk of glacier lake outburst floods and floods from landslides into moraine-dammed lakes is increasing in Asian high mountains ( ''high confidence'' ) ( [[#Haeberli--2017|Haeberli et al., 2017]] ; [[#Kapitsa--2017|Kapitsa et al., 2017]] ; [[#Bajracharya--2018|Bajracharya et al., 2018]] ; [[#Narama--2018|Narama et al., 2018]] ; S. [[#Wang--2020|]] [[#Wang--2020|Wang et al., 2020]] ).

'''Permafrost''' : Permafrost is thawing in Asia ( ''high confidence'' ). Temperatures in the cold continuous permafrost of north-eastern East Siberia rose from the 1980s up to 2017, and the active layer thicknesses in Siberia and Russian Far East generally increased from late 1990s to 2017 ( [[#Romanovsky--2018|Romanovsky et al., 2018]] ). The change in mean annual ground temperature for northern Siberia is about +0.1 to +0.3°C per decade since 2000 ( [[#Romanovsky--2018|Romanovsky et al., 2018]] ). Ground temperature in the permafrost regions of TIB (taking 40% of TIB currently) increased (0.02–0.26°C per decade for different boreholes) during 1980 to 2018, and the active layer thickened at a rate of 19.5 cm per decade (L. [[#Zhao--2020|]] [[#Zhao--2020|Zhao et al., 2020]] ). There is ''high confidence'' that permafrost in Asian high mountains will continue to thaw and the active layer thickness will increase ( [[#Bolch--2019|Bolch et al., 2019]] ). The permafrost area is projected to decline by 13.4–27.7% and 60–90% in TIB (L. [[#Zhao--2020|]] [[#Zhao--2020|Zhao et al., 2020]] ) and 32% ± 11% and 76% ± 12% in Russia ( [[#Guo--2016|Guo and Wang, 2016]] ) by the end of the 21st century under the RCP2.6 and RCP8.5 scenarios respectively ( ''high confidence'' ).

'''Lake and river ice:''' Lake ice cover duration got shorter in many lakes in TIB ( [[#Yao--2016|Yao et al., 2016]] ; [[#Cai--2019|Cai et al., 2019]] ; [[#Guo--2020|Guo et al., 2020]] ) and some other areas such as north-west China ( [[#Cai--2020|Cai et al., 2020]] ) and north-east China ( [[#Yang--2019|Yang et al., 2019]] ) in the last two decades ( ''high confidence'' ). River ice cover extent decreased in TIB as well (H. [[#Li--2020|]] [[#Li--2020|]] [[#Li--2020|Li et al., 2020]] ; [[#Yang--2020a|Yang et al., 2020a]] ). Climate warming also leads to a significant reduction in the period with ice phenomena and the decrement of ice regime hazard in Russian lowland rivers ( [[#Agafonova--2017|Agafonova et al., 2017]] ), and the Inner Mongolia reach of the Yellow River in northern China ( [[#Wan--2020|Wan et al., 2020]] ) ( ''high confidence'' ). Lake ice and river ice in Asia are expected to decline with projected increases in surface air temperature towards the end of this century ( ''high confidence'' ) ( [[#Guo--2020|Guo et al., 2020]] ; [[#Yang--2020a|Yang et al., 2020a]] ).

'''Heavy snowfall and ice storm:''' Observed trends in heavy snowfall and ice storms are uncertain. Annual maximum snow depth decreased for the period between 1962 and 2016 on the western side of both eastern and western Japan, at rates of 12.3% and 14.6% per decade respectively ( [[#MOE--2018|MOE et al., 2018]] ). Observational results generally show a decrease in the frequency and an increase in the mean intensity of snowfalls in most Chinese regions ( ''medium confidence'' ) ( [[#Zhou--2018|]] [[#Zhou--2018|B. Zhou et al., 2018]] ). Because of the decrease in the snow frequency, the occurrence of large-scale snow disasters in TIB decreased ( ''low confidence'' ) ( [[#Qiu--2018|Qiu et al., 2018]] ; S. [[#Wang--2019|]] [[#Wang--2019|]] [[#Wang--2019|]] [[#Wang--2019|Wang et al., 2019]] ). Large parts of northern high-latitude continents (including Siberia and RFE) have experienced cold snaps and heavy snowfalls in the past few winters, and the reduction of Arctic sea ice would increase the chance of heavy snowfall events in those regions in the coming decades ( ''medium confidence'' ) ( [[#Song--2017|Song and Liu, 2017]] ). Heavy snowfall is projected to occur more frequently in Japan’s Northern Alps, the inland areas of Honshu Island and Hokkaido Island ( [[#Kawase--2016|Kawase et al., 2016]] , 2020; [[#MOE--2018|MOE et al., 2018]] ), and the heavy wet snowfall can be enhanced over the mountainous regions in central Japan and northern part of Japan ( [[#Ohba--2020|Ohba and Sugimoto, 2020]] ) ( ''medium confidence'' ).

'''Hail:''' The hailstorm in the Asian region shows a decreasing trend in several regions ( ''low confidence'' , ''limited evidence'' ). In China severe weather days including thunderstorms, hail and/or damaging wind have decreased by 50% from 1961 to 2010 (M. [[#Li--2016|]] [[#Li--2016|]] [[#Li--2016|Li et al., 2016]] ; [[#Zhang--2017|Zhang et al., 2017]] ), and the hail size decreased since 1980 ( [[#Ni--2017|Ni et al., 2017]] ). A rate of decrease of 0.214 hail days per decade has also been reported for Mongolia between 1984–2013, where the annual number of hail days averaged is 0.74 ( [[#Lkhamjav--2017|Lkhamjav et al., 2017]] ).

'''Snow avalanche:''' There is as yet ''limited evidence'' for the evolution of avalanches in Asia. Tree-ring-based snow avalanche reconstructions in the Indian Himalayas show an increase in avalanche occurrence and runout distances in recent decades ( [[#Ballesteros-Cánovas--2018|Ballesteros-Cánovas et al., 2018]] ).

'''In summary, snowpack and glaciers are projected to continue decreasing and permafrost to continue thawing in Asia''' ( high confidence '''). There is''' medium confidence '''of increasing heavy snowfall in some regions, but''' limited evidence '''on future changes in hail and snow avalanches.'''

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<span id="coastal-and-oceanic-1"></span>
==== 12.4.2.5 Coastal and Oceanic ====

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'''Relative sea level:''' Around Asia, from 1900–2018, a new tide gauge-based reconstruction finds a regional mean RSL change of 1.33 [0.80 to 1.86] mm yr <sup>–1</sup> in the Indian Ocean–Southern Pacific and 1.68 [1.27 to 2.09] mm yr <sup>–1</sup> in the North-west Pacific ( [[#Frederikse--2020|Frederikse et al., 2020]] ), compared to a GMSL change of around 1.7 mm yr <sup>–1</sup> [[IPCC:Wg1:Chapter:Chapter-2#2.3.3.3|Section 2.3.3.3]] and Table 9.5). For the period 1993–2018, the RSLR rates around Asia, based on satellite altimetry, increased to 3.65 [3.23 to 4.08] mm yr <sup>–1</sup> and 3.53 [2.64 to 4.45] mm yr <sup>–1</sup> respectively ( [[#Frederikse--2020|Frederikse et al., 2020]] ), compared to a GMSL change of 3.25 mm yr <sup>–1</sup> [[IPCC:Wg1:Chapter:Chapter-2#2.3.3.3|Section 2.3.3.3]] and Table 9.5). The rate of RSLR along the coastline of China ranges from –2.3 ± 1.9 to +5.7 ± 0.4 mm yr <sup>–1</sup> during 1980–2016; after removing the vertical land movement, the average rate of sea level rise is 2.9 ± 0.8 mm yr <sup>–1</sup> over 1980–2016 and 3.2 ± 1.1 mm yr <sup>–1</sup> since 1993 ( [[#Qu--2019|Qu et al., 2019]] ). However, the rates of land subsidence reported by [[#Minderhoud--2017|Minderhoud et al. (2017)]] are substantially higher than those reported by [[#Qu--2019|Qu et al. (2019)]] . RSL change in many coastal areas in Asia, especially in EAS, is affected by land subsidence due to sediment compaction under building mass and groundwater extraction ( ''high confidence'' ) ( [[#Erban--2014|Erban et al., 2014]] ; [[#Nicholls--2015|Nicholls, 2015]] ; [[#Minderhoud--2019|Minderhoud et al., 2019]] ; [[#Qu--2019|Qu et al., 2019]] ). During 1991–2016, the Mekong Delta in Vietnam sank on average about 18 cm as a consequence of groundwater withdrawal, and the subsidence related to groundwater extraction has gradually increased with highest sinking rates estimated to be 11 mm yr <sup>–1</sup> in 2015 ( [[#Minderhoud--2017|Minderhoud et al., 2017]] ).

Relative sea level rise is ''very likely'' to continue in the oceans around Asia. Regional mean RSLR projections for the oceans around Asia range from 0.3–0.5 m under SSP1-2.6 to 0.7–0.8 m under SSP5-8.5 for 2081–2100 relative to 1995–2014 (median values), which is within the range of projected GMSL change ( [[IPCC:Wg1:Chapter:Chapter-9#9.6.3.3|Section 9.6.3.3]] ). These RSLR projections may, however, be underestimated due to potential partial representation of land subsidence in their assessment ( [[IPCC:Wg1:Chapter:Chapter-9#9.6.3.2|Section 9.6.3.2]] ).

'''Coastal flood:''' The present-day 1-in-100-year ETWL is between 0.5–8 m around Asia, with values above 2.5 m or above common along the coasts of Central and north-eastern Asia ( [[#Vousdoukas--2018|Vousdoukas et al., 2018]] ; [[#Kirezci--2020|Kirezci et al., 2020]] ). Sea level rise and land subsidence will jointly lead to more flooding in delta areas in Asia ( ''high confidence'' ) ( [[#Takagi--2016|Takagi et al., 2016]] ; J. [[#Wang--2018|]] [[#Wang--2018|Wang et al., 2018]] ).

Extreme total water level magnitude and occurrence frequency are expected to increase throughout the region ( ''high confidence'' ) (Figure 12.4p–r and Figure 12.SM.6). Across the region, the 5–95th percentile range of the 1-in-100-year ETWL is projected to increase (relative to 1980–2014) by 7–44 cm and by 10–52 cm by 2050 under RCP4.5 and RCP8.5 respectively. By 2100, this range is projected to be 11–91 cm and 28–187 cm under RCP4.5 and RCP8.5 respectively ( [[#Vousdoukas--2018|Vousdoukas et al., 2018]] ; [[#Kirezci--2020|Kirezci et al., 2020]] ). Furthermore, the present-day 1-in-100-year ETWL is projected to have median return periods of around 1-in-50-years by 2050 and 1-in-10-years by 2100 under RCP4.5 in most of Asia, except SEA and ARP, in which the present-day 1-in-100-year ETWL is projected occur once per year or more, both by 2050 and 2100 ( [[#Vousdoukas--2018|Vousdoukas et al., 2018]] ). The present-day 1-in-50-year ETWL is projected to occur around three times a year by 2100 with a SLR of 1 m across Asia ( [[#Vitousek--2017|Vitousek et al., 2017]] ). Compound impacts of precipitation change, land subsidence, sea level rise, upstream hydropower development, and local water infrastructure development may lead to larger flood extent and prolonged inundation in the Vietnamese Mekong Delta ( [[#Triet--2020|Triet et al., 2020]] ).

'''Coastal erosion:''' Over the past 30 years, South, South East and East Asia exhibit the most pronounced delta changes globally due to strong human-induced changes to the fluvial sediment flux ( [[#Nienhuis--2020|Nienhuis et al., 2020]] ). Satellite derived shoreline change estimates over 1984–2015 indicate shoreline retreat rates between 0.5 m yr <sup>–1</sup> and 1 m yr <sup>–1</sup> along the coasts of WCA and ARP, increasing to 3 m yr <sup>–1</sup> in SAS. Over the same period, shoreline progradation has been observed along the coasts of RFE (0.2 m yr <sup>–1</sup> ), SEA (0.1 m yr <sup>–1</sup> ) and EAS (0.5 m yr <sup>–1</sup> ) ( [[#Luijendijk--2018|Luijendijk et al., 2018]] ; [[#Mentaschi--2018|Mentaschi et al., 2018]] ). Meanwhile, there has been a gross coastal area loss of 3,590 km <sup>2</sup> in South Asia, and a loss of 2,350 km <sup>2</sup> in Pacific Asia, over a 30-year period (1984–2015) ( [[#Mentaschi--2018|Mentaschi et al., 2018]] ).

Projections indicate that a majority of sandy coasts in the Asia region will experience shoreline retreat ( ''high confidence'' ) ( [[#Udo--2017|Udo and Takeda, 2017]] ; [[#Ritphring--2018|Ritphring et al., 2018]] ; [[#Vousdoukas--2020b|Vousdoukas et al., 2020b]] ), while parts of the RFE, EAS, SEA and WCA coastline are projected to prograde over the 21st century, if present ambient shoreline change trends continue. Median shoreline change projections (CMIP5), relative to 2010, presented by [[#Vousdoukas--2020b|Vousdoukas et al. (2020b)]] show that, by mid-century, sandy shorelines in Asia will retreat by between 10–50 m, except in SAS where shoreline retreat is projected to exceed 100 m, under both RCP4.5 and RCP8.5. By 2100, and under RCP4.5, shoreline retreats of around 85, 100 and 300 m are projected along the sandy coastlines of SEA and WCA, ARP and SAS respectively (50 m or less in other Asian regions), while under RCP8.5, over the same period, sandy shorelines along all regions with coastlines, except RFE and EAS, are projected to retreat by more than 100 m, with the retreat in SAS reaching 350 m (2100 RCP8.5 projections for RFE and EAS are about 60 m and about 85 m respectively; Figure 12.6).

'''Marine heatwave:''' There have been frequent marine heatwaves (MHW) in the coastal oceans of Asia, connected to the increase between 0.25°C and 1°C in mean SST of the coastal oceans since 1982–1998 ( [[#Oliver--2018|Oliver et al., 2018]] ). There is ''high confidence'' that MHWs will increase around most of Asia. Mean SST is projected to increase by 1°C (2°C) around Asia by 2100, with a hotspot of around 2°C (5°C) along the coastlines of the Sea of Japan and the RFE under RCP4.5 (RCP8.5; Interactive Atlas). Under global warming conditions, MHW intensity and duration are projected to increase in the coastal zones of all sub-regions of Asia, but most notably in SEA and SAS ( [[#Frölicher--2018|Frölicher et al., 2018]] ). Projections for SSP1-2.6 and SSP5-8.5 both show an increase in MHWs around Asia by 2081–2100, relative to 1985–2014 (Box 9.2, Figure 1).

'''In general, there is''' high confidence '''that most coastal/ocean-related climatic impact-drivers in Asia will increase over the 21st century. Relative sea level rise is''' very likely '''to continue around Asia, contributing to increased coastal flooding in low-lying areas''' ( high confidence ''') and shoreline retreat along most sandy coasts''' ( high confidence '''). Marine heatwaves are also expected to increase around the region over the 21st century''' ( high confidence ''').'''

The assessed direction of change in climatic impact-drivers for Asia and associated confidence levels are illustrated in Table 12.4.

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'''Table 12.4''' '''|''' '''Summary of confidence in direction of projected change in climatic impact-drivers in Asia, representing their aggregate characteristic changes for mid-century for scenarios RCP4.5, SSP2-4.5, SRES A1B or above within each AR6 region (defined in Chapter 1), approximately corresponding (for CIDs that are independent of sea level rise) to global warming levels between 2°C and 2.4°C (see [[#12.4|Section 12.4]] for more details of the assessment method).''' The table also includes the assessment of observed or projected time-of-emergence of the CID change signal from the natural interannual variability if found with at least ''medium confidence'' in [[#12.5.2|Section 12.5.2]] .

[[File:70f9e96f64e1f7863919397ba6aa2df7 IPCC_AR6_WGI_Chapter12_Table_12_4.jpg]]

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<span id="australasia"></span>