27 Sea Level Rise Sea level rise is caused by thermal expansion of water in the seas due to their warming, as well as the increase of the amount of water due to the melting of the cryosphere. From 2006-2015, the sum of ice sheets and glacier melt contributions has been the dominant source of sea level rise, exceeding that of thermal expansion.114 The findings of the IPCC provide that the rise of global mean sea level (GMSL) in the 20th century is at a rate faster than any preceding century in at least the last three millennia. Between 2006 and 2018, the average rate of sea level rise was 3.7 mm per year.115 Since 1901, GMSL has risen by 0.20 [0.15-0.25] m, and the rate is accelerating116 due to the combined increased ice loss from the Greenland and Antarctic ice sheets. Ocean Acidification Ocean acidification occurs when oceans absorb CO2. The IPCC reports provide that the ocean has been absorbing more CO2 and has undergone increasing surface acidification. The ocean has taken up between 20 to 30 percent of total anthropogenic CO2 emissions since the 1980s.117 This has resulted in ocean surface pH declining globally over the past four decades and in all ocean basins in the ocean interior over the past two to three decades.118 3. Cryosphere Loss The cryosphere refers to the portions of the Earth System that is frozen such as glaciers, ice sheets, icebergs, sea ice, snow cover, and the like.119 It is inherently reactive to temperature changes and “provides some of the most visible signatures of climate change.”120 Over the last few decades, the cryosphere has seen widespread 114 IPCC SROCC SPM, supra note 111. 115 IPCC, AR 6, WG1, SPM, supra note 107. 116 Id. 117 IPCC SROCC SPM, supra note 111. 118 IPCC, AR 6, WG1, SPM, supra note 107. 119 IPCC SROCC SPM, supra note 111. 120 Intergovernmental Panel on Climate Change, Observations: Cryosphere, in Climate Change 2013 – The Physical Science Basis: Working Group I Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change 317-382 (Cambridge University Press, 2014). doi:10.1017/ CBO9781107415324.012 [hereinafter referred to us IPCC Observations: Cryosphere].