Editing IPCC:AR6/SROCC/Chapter-4 (section)

===== 4.2.2.5.2 Attribution of global mean sea level change to anthropogenic forcing =====

By estimating a probabilistic upper range of long-term persistent natural sea level variability, Dangendorf et al. (2015) <sup>[[#fn:r356|356]]</sup> detected a fraction of observed sea level change that is unexplained by natural variability and concluded by inference that it is ''virtually certain'' that at least 45% of the observed increase in GMSL since 1900 is attributable to anthropogenic forcing. Similarly, Becker et al. (2014) provided statistical evidence that the observed sea level trend, both in the global mean and at selected tide gauge locations, is not consistent with unforced, internal variability. They inferred that more than half of the observed GMSL trend during the 20th century is attributable to anthropogenic forcing.

Slangen et al. (2016) <sup>[[#fn:r357|357]]</sup> reconstructed GMSL from 1900 to 2005 based on CMIP5 model simulations separating individual components of radiative climate forcing and combining the contributions of thermosteric sea level change with glacier and ice sheet mass loss. They found that the naturally caused sea level change, including the long-term adjustment of sea level to climate change preceding 1900, caused 67 ± 23% of observed change from 1900 to 1950, but only 9 ± 18% between 1970 and 2005. Anthropogenic forcing was found to have caused 15 ± 55% of observed sea level change during 1900–1950, but 69 ± 31% during 1970–2005. The sum of all contributions explains only 74 ± 22% of observed GMSL change during the period 1900–2005 considering the mean of the reconstructions of Church and White (2011) <sup>[[#fn:r358|358]]</sup> , Ray and Douglas (2011) , Jevrejeva et al. (2014b) and Hay et al. (2015) . However, the budget could be closed taking into contribution of glaciers that are missing from the global glacier inventory or have already melted (Parkes and Marzeion, 2018 <sup>[[#fn:r361|361]]</sup> ) which were not considered in Slangen et al. (2016) <sup>[[#fn:r362|362]]</sup> .

Based on these multiple lines of evidence, there is ''high confidence'' that anthropogenic forcing ''very likely'' is the dominant cause of observed GMSL rise since 1970.

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