Editing IPCC:AR6/WGI/Chapter-9 (section)

=== Sea Ice ===

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'''The Arctic Ocean will''' ''likely'' '''become practically sea ice free''' <sup>[[#footnote-004|1]]</sup> '''during the seasonal sea ice minimum for the first time before 2050 in all considered SSP scenarios. There is no tipping point for this loss of Arctic summer sea ice''' ( ''high confidence'' ''').''' The practically ice-free state is projected to occur more often with higher greenhouse gas concentrations, and it will become the new normal for high-emissions scenarios by the end of this century ( ''high confidence'' ). Based on observational evidence, Coupled Model Intercomparison Project Phase 6 (CMIP6) models and conceptual understanding, the substantial satellite-observed decrease of Arctic sea ice area over the period 1979 '''–''' 2019 is well described as a linear function of global mean surface temperature, and thus of cumulative anthropogenic carbon dioxide (CO <sub>2</sub> ) emissions, with superimposed internal variability ( ''high confid'' ''ence'' ). According to both process understanding and CMIP6 simulations, a practically sea ice-free state will ''likely'' be observed some years before additional (post-2020) cumulative anthropogenic CO <sub>2</sub> emissions reach 1000 GtCO <sub>2</sub> . {4.3.2, 9.3.1}

'''For Antarctic sea ice, regionally opposing trends and large interannual variability result in no significant trend in satellite-observed sea ice area from 1979 to 2020 in both winter and summer''' ( ''high confidence'' ''').''' The regionally opposing trends result primarily from changing regional wind forcing ( ''medium confidence'' ). There is ''low confidence'' in model simulations of future Antarctic sea ice decrease, and lack of decrease, due to deficiencies of process representation, in particular at the regional level. {2.3.2, 9.2.3, 9.3.2}

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