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

==== 2.3.3.4 Observed Loss of Ice ====

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Studies since AR5 have confirmed ongoing and accelerating loss of lake and river ice in the Northern Hemisphere ( ''robust evidence'' , ''high agreement'' ) (Figure 2.4). In recent decades, systems have been freezing later in winter and thawing earlier in spring, reducing ice duration by &gt;2 weeks per year and leading to an increasing numbers of years with a loss of perennial ice cover, intermittent ice cover or even an absence of ice ( [[#Adrian--2009|Adrian et al., 2009]] ; [[#Kirillin--2012|Kirillin et al., 2012]] ; [[#Paquette--2015|Paquette et al., 2015]] ; [[#Adrian--2016|Adrian et al., 2016]] ; [[#Park--2016|Park et al., 2016]] ; [[#Roberts--2017|Roberts et al., 2017]] ; [[#Sharma--2019|Sharma et al., 2019]] ). The global extent of river ice declined by 25% between 1984 and 2018 ( [[#Yang--2020|Yang et al., 2020]] ). This trend has been more pronounced at higher latitudes, consistent with enhanced polar warming (large geographic coverage) ( [[#Du--2017|Du et al., 2017]] ). Empirical long-term and remote-sensing data gathered in an increasingly large number of freshwater systems supports ''very high confidence'' in attributing these trends to climate change. For the decline of glaciers, snow and permafrost, see [[IPCC:Wg2:Chapter:Chapter-4|Chapter 4]] (this report) and the Special Report on the Ocean and Cryosphere in a Changing Climate ( [[#IPCC--2019b|IPCC, 2019b]] ).

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'''Figure 2.4 | Global ice cover trends of lakes and rivers.'''

'''(a)''' Spatial distribution of current (light grey areas) and future (coloured areas) Northern Hemisphere lakes that may experience intermittent winter ice cover with climate warming. Projections were based on current conditions (1970–2010) and four established air temperature projections (Data source: ( [[#Sharma--2019|Sharma et al., 2019]] ).

'''(b)''' Spatial distribution of projected change in Northern Hemisphere river ice duration under the RCP4.5 emission scenario by 2080–2100 relative to the period 2009–2029. White areas refer to rivers without ice cover in the period 2009–2029 (zero days). Reference period isolines indicate river ice duration in the period 2009–2029. Coloured areas depict loss of ice duration in days. Blue areas depict a projected increase in river ice duration. Grey land areas indicate a lack of Landsat-observable rivers (Data source: ( [[#Yang--2020|Yang et al., 2020]] ).

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