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

=== Changes in Modes of Variability ===

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'''Since the late 19th century, major modes of climate variability show no sustained trends but do exhibit fluctuations in frequency and magnitude at inter-decadal time scales, with the notable exception of the Southern Annular Mode, which has become systematically more positive''' ( ''high confidence'' '''). There is''' ''high confidence'' '''that these modes of variability have existed for millennia or longer, but''' ''low confidence'' '''in detailed reconstructions of most modes prior to direct instrumental records.''' Both polar annular modes have exhibited strong positive trends toward increased zonality of mid-latitude circulation over multi-decadal periods, but these trends have not been sustained for the Northern Annular Mode since the early 1990s ( ''high confidence'' ). For tropical ocean modes, a sustained shift beyond multi-centennial variability has not been observed for El Niño–Southern Oscillation ( ''medium confidence'' ), but there is ''limited evidence'' and ''low agreement'' about the long-term behaviour of other tropical ocean modes. Modes of decadal and multi-decadal variability over the Pacific and Atlantic oceans exhibit no significant trends over the period of observational records ( ''high confidence'' ). {2.4}

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