Editing IPCC:AR6/WGII/Chapter-2 (section)

==== 2.3.3.2 Observed Changes in Water Level ====

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Depending on how the intensification of the global water cycle affects individual lake water budgets, the amount of water stored in specific lakes may increase, decrease or have no substantial cumulative effect ( [[#Notaro--2015|Notaro et al., 2015]] ; [[#Pekel--2016|Pekel et al., 2016]] ; [[#Rodell--2018|Rodell et al., 2018]] ; [[#Busker--2019|Busker et al., 2019]] ; [[#Woolway--2020b|Woolway et al., 2020b]] ). The magnitude of hydrological changes that can be assuredly attributed to climate change remains uncertain ( [[#Hegerl--2015|Hegerl et al., 2015]] ; [[#Gronewold--2019|Gronewold and Rood, 2019]] ; [[#Kraemer--2020|Kraemer et al., 2020]] ). Attribution of water storage variation in lakes due to climate change is facilitated when such variations occur coherently across broad geographic regions and long time scales, preferably absent of other anthropogenic hydrological influences ( [[#Watras--2014|Watras et al., 2014]] ; [[#Kraemer--2020|Kraemer et al., 2020]] ). There is increasing awareness that climate change contributes to the loss of small temporary ponds which cover a greater global area than lakes ( [[#Bagella--2016|Bagella et al., 2016]] ).

Lakes fed by glacial melt water are growing in response to climate change and glacier retreat ( ''robust evidence'' , ''high agreement'' ) ( [[#Shugar--2020|Shugar et al., 2020]] ). Water storage increases on the Tibetan Plateau (Figure 2.3a) have been attributed to changes in glacier melt, permafrost thaw, precipitation and runoff, in part as a result of climate change ( [[#Huang--2011|Huang et al., 2011]] ; [[#Meng--2019|Meng et al., 2019]] ; [[#Wang--2020a|Wang et al., 2020a]] ). ''High confidence'' in attribution of these trends to climate change is supported by long-term ground survey data and observations from the Gravity Recovery and Climate Experiment (GRACE) satellite mission ( [[#Ma--2010|Ma et al., 2010]] ; [[#Rodell--2018|Rodell et al., 2018]] ; [[#Kraemer--2020|Kraemer et al., 2020]] ).

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'''Figure 2.3 | Change in water extent in the Tibetan Plateau and annual mean global river flow.'''

'''(a)''' Changes in water storage on the Tibetan Plateau. Map of the Qinghai–Tibetan Plateau, Asia, showing the percent change in surface water extent from 1984 to 2019 based on LANDSAT imagery. Increases in surface water extent in this region are mainly caused by climate change-mediated increases in precipitation and glacial melt (Source: EC JRC/Google; ( [[#Pekel--2016|Pekel et al., 2016]] ).

'''(b)''' Global map of the median trend in annual mean river flow derived from 7250 observatories around the world (in 1971–2010). Some regions are drying (northeast Brazil, southern Australia and the Mediterranean) and others are wetting (northern Europe), mainly caused by large-scale shifts in precipitation, changes in factors that influence evapotranspiration and alterations of the timing of snow accumulation and melt driven by rising temperatures (Source: ( [[#Gudmundsson--2021|Gudmundsson et al., 2021]] ).

In the Arctic, lake area has increased in regions with continuous permafrost, and decreased in regions where permafrost is thinner and discontinuous ( ''robust evidence'' , ''high agreement'' ) (See Chapter 4) ( [[#Smith--2005|Smith et al., 2005]] ; [[#Andresen--2015|Andresen and Lougheed, 2015]] ; [[#Nitze--2018|Nitze et al., 2018]] ; [[#Mekonnen--2021|Mekonnen et al., 2021]] ).

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