Sea level rise is the long-term increase in global mean sea level driven primarily by ocean warming and land ice loss. Observed rates have accelerated in recent decades, and future rise is projected for centuries under all emissions scenarios, posing extensive risks to coastal systems and low‑lying communities worldwide.
Last updated March 26, 2026
Global mean sea level; primary drivers: thermal expansion and land ice mass loss; observed acceleration; projections to 2100 and beyond.
Definition and Measurement
Sea level rise is the long-term increase in global mean sea level (GMSL) driven mainly by ocean thermal expansion and the addition of water from melting glaciers and ice sheets, with smaller contributions from changes in land water storage IPCC AR6 WGI SPM. GMSL is measured by satellite altimeters since 1993 and by coastal tide gauges over longer periods; tide gauges reflect relative sea level changes influenced by vertical land motion and local processes, whereas satellites provide near‑global coverage of ocean height NOAA Ocean Service.
Observed Changes
Between 1901 and 2018, GMSL increased by 0.20 m (likely range 0.15–0.25 m) IPCC AR6 WGI SPM. Since 1880, global average sea level has risen about 21–24 cm NOAA Climate.gov. Satellite altimetry shows a rise of roughly 10.1 cm since 1993 to the latest data NASA JPL Vital Signs and 98.8 mm as displayed on the NASA Sea Level Change Portal NASA Sea Level Portal. The rate of rise has accelerated: 3.7 mm/yr (likely 3.2–4.2) during 2006–2018 IPCC AR6 WGI SPM, with a current annual rate around 0.44 cm/yr (~4.4 mm/yr) based on the multi‑mission satellite record NASA Sea Level Portal. In 2023, the annual global mean reached about 101.4 mm above the 1993 average, a record in the satellite era NOAA Climate.gov; recent global assessments also report record‑high sea level and continued acceleration WMO.
Physical Drivers
Heating of the climate system raises sea level through ocean expansion and land ice mass loss. For 1971–2018, thermal expansion accounted for about 50 % of observed GMSL rise, glaciers 22 %, ice sheets 20 %, and changes in land‑water storage 8 % (high confidence) IPCC AR6 WGI SPM. Observations indicate strongly increased ice‑sheet mass loss since the 1990s, making glacier and ice‑sheet contributions dominant in 2006–2018 IPCC AR6 WGI SPM. Regional sea level varies due to ocean dynamics, gravitational and rotational effects of changing ice mass, and vertical land motion, leading to local departures from the global mean NOAA Ocean Service.
Projections
It is virtually certain that GMSL will continue to rise throughout the 21st century and beyond. Relative to 1995–2014, likely GMSL rise by 2100 is 0.28–0.55 m under very low emissions (SSP1‑1.9) and 0.63–1.01 m under very high emissions (SSP5‑8.5); by 2150 it is 0.37–0.86 m (SSP1‑1.9) and 0.98–1.88 m (SSP5‑8.5) (medium confidence) IPCC AR6 WGI SPM, IPCC AR6 SYR Fig. 3.4. Low‑likelihood, high‑impact outcomes with higher rise (approaching ~2 m by 2100 under SSP5‑8.5) cannot be ruled out due to deep uncertainty in ice‑sheet processes IPCC AR6 WGI SPM. On multi‑millennial timescales, committed rise is on the order of meters even if global warming stabilizes, reflecting slow deep‑ocean warming and ice‑sheet response IPCC AR6 WGI SPM.
Impacts and Extremes
Rising mean sea level increases the frequency and severity of coastal flooding and erosion. Events that historically occurred once per century are projected to occur at least annually by 2100 at more than half of tide‑gauge locations due to relative sea level rise (high confidence) IPCC AR6 WGI SPM. High‑tide (nuisance) flooding has already increased dramatically in many U.S. coastal communities relative to 50 years ago NOAA Ocean Service. Regional relative sea level rise will be within ±20 % of the global mean along roughly two‑thirds of coastlines, with local departures driven by vertical land motion and oceanographic factors IPCC AR6 WGI SPM.
Monitoring and Data
Continuous monitoring uses satellite radar altimetry (e.g., TOPEX/Poseidon, Jason series, Sentinel‑6 Michael Freilich) to measure sea surface height globally and tide‑gauge networks to track relative sea level at coasts NASA JPL Vital Signs, NOAA Ocean Service. Multi‑mission satellite records show an accelerating rise, with the latest indicators reporting a current rate near 0.44 cm/yr and a cumulative increase near 10 cm since 1993 NASA Sea Level Portal, NASA JPL Vital Signs. Tide‑gauge reconstructions and satellite data together underpin historical estimates, including an 8–9 inch rise since 1880 NOAA Climate.gov.
Sea level rise is the long-term increase in global mean sea level driven primarily by ocean warming and land ice loss. Observed rates have accelerated in recent decades, and future rise is projected for centuries under all emissions scenarios, posing extensive risks to coastal systems and low‑lying communities worldwide.
Last updated March 26, 2026
Global mean sea level; primary drivers: thermal expansion and land ice mass loss; observed acceleration; projections to 2100 and beyond.
Definition and Measurement
Sea level rise is the long-term increase in global mean sea level (GMSL) driven mainly by ocean thermal expansion and the addition of water from melting glaciers and ice sheets, with smaller contributions from changes in land water storage IPCC AR6 WGI SPM. GMSL is measured by satellite altimeters since 1993 and by coastal tide gauges over longer periods; tide gauges reflect relative sea level changes influenced by vertical land motion and local processes, whereas satellites provide near‑global coverage of ocean height NOAA Ocean Service.
Observed Changes
Between 1901 and 2018, GMSL increased by 0.20 m (likely range 0.15–0.25 m) IPCC AR6 WGI SPM. Since 1880, global average sea level has risen about 21–24 cm NOAA Climate.gov. Satellite altimetry shows a rise of roughly 10.1 cm since 1993 to the latest data NASA JPL Vital Signs and 98.8 mm as displayed on the NASA Sea Level Change Portal NASA Sea Level Portal. The rate of rise has accelerated: 3.7 mm/yr (likely 3.2–4.2) during 2006–2018 IPCC AR6 WGI SPM, with a current annual rate around 0.44 cm/yr (~4.4 mm/yr) based on the multi‑mission satellite record NASA Sea Level Portal. In 2023, the annual global mean reached about 101.4 mm above the 1993 average, a record in the satellite era NOAA Climate.gov; recent global assessments also report record‑high sea level and continued acceleration WMO.
Physical Drivers
Heating of the climate system raises sea level through ocean expansion and land ice mass loss. For 1971–2018, thermal expansion accounted for about 50 % of observed GMSL rise, glaciers 22 %, ice sheets 20 %, and changes in land‑water storage 8 % (high confidence) IPCC AR6 WGI SPM. Observations indicate strongly increased ice‑sheet mass loss since the 1990s, making glacier and ice‑sheet contributions dominant in 2006–2018 IPCC AR6 WGI SPM. Regional sea level varies due to ocean dynamics, gravitational and rotational effects of changing ice mass, and vertical land motion, leading to local departures from the global mean NOAA Ocean Service.
Projections
It is virtually certain that GMSL will continue to rise throughout the 21st century and beyond. Relative to 1995–2014, likely GMSL rise by 2100 is 0.28–0.55 m under very low emissions (SSP1‑1.9) and 0.63–1.01 m under very high emissions (SSP5‑8.5); by 2150 it is 0.37–0.86 m (SSP1‑1.9) and 0.98–1.88 m (SSP5‑8.5) (medium confidence) IPCC AR6 WGI SPM, IPCC AR6 SYR Fig. 3.4. Low‑likelihood, high‑impact outcomes with higher rise (approaching ~2 m by 2100 under SSP5‑8.5) cannot be ruled out due to deep uncertainty in ice‑sheet processes IPCC AR6 WGI SPM. On multi‑millennial timescales, committed rise is on the order of meters even if global warming stabilizes, reflecting slow deep‑ocean warming and ice‑sheet response IPCC AR6 WGI SPM.
Impacts and Extremes
Rising mean sea level increases the frequency and severity of coastal flooding and erosion. Events that historically occurred once per century are projected to occur at least annually by 2100 at more than half of tide‑gauge locations due to relative sea level rise (high confidence) IPCC AR6 WGI SPM. High‑tide (nuisance) flooding has already increased dramatically in many U.S. coastal communities relative to 50 years ago NOAA Ocean Service. Regional relative sea level rise will be within ±20 % of the global mean along roughly two‑thirds of coastlines, with local departures driven by vertical land motion and oceanographic factors IPCC AR6 WGI SPM.
Monitoring and Data
Continuous monitoring uses satellite radar altimetry (e.g., TOPEX/Poseidon, Jason series, Sentinel‑6 Michael Freilich) to measure sea surface height globally and tide‑gauge networks to track relative sea level at coasts NASA JPL Vital Signs, NOAA Ocean Service. Multi‑mission satellite records show an accelerating rise, with the latest indicators reporting a current rate near 0.44 cm/yr and a cumulative increase near 10 cm since 1993 NASA Sea Level Portal, NASA JPL Vital Signs. Tide‑gauge reconstructions and satellite data together underpin historical estimates, including an 8–9 inch rise since 1880 NOAA Climate.gov.
