Sea Level

Sea level change is an important climate diagnostic. However, interpretation of the moderate rate of sea level rise of the past century is complicated by the fact that several competing processes contribute to net sea level change. The most important processes are melting of land ice (the large ice sheets on Greenland and Antarctica and mountain glaciers) and thermal expansion of ocean water as the ocean warms. Storage of water behind dams and depletion of groundwater aquifers also affect sea level.

Over the past 5000 years the average rate of sea level rise was much less than 1 meter per millennium (1 mm/year), as shown by geologic markers on coastlines. In the past century tide gauges at coastal cities reveal a larger rate of sea level rise. The second chart below shows that sea level rose about 2 mm/year during 1920-2000.

Satellites began to measure sea level precisely in 1993. Since then sea level has been rising about 3.6 mm/year. This rate is equal to just over one foot per century. The impact of such sea level change is substantial, yet the concern is that far greater sea level rise will occur this century if the major ice sheets disintegrate.

Global sea level change measured by TOPEX satellite (1992-2001), Jason-1 (2002-mid 2008), Jason-2 (mid 2008-2015), Jason-3 (2016-2020) and Sentinel-6 MF (2022-2025). Data source: University of Colorado at Boulder (data through March 7, 2025) and AVISO (data through November 11, 2025)

in PDF (Last modified: 2026/01/05)

Sea level change for 1900-1992, based on tide gauge measurements, from J.A. Church and N.J. White "Sea-level rise from the late 19th to the early 21st Century" Surveys in Geophysics (2011), but multiplied by 0.78 to have 1901-1990 trend as 1.2 mm/yr as stated in C.C. Hay, et al. "Probabilistic reanalysis of twentieth-century sea-level rise", Nature (2015). 1993-2025 data are cnes AVISO. Figure also available in PDF. (Last modified: 2026/01/05)