Michaël Ablain (Magellium, France); Benoit Meyssignac (LEGOS, France); Emma Wooliams (NPL, UK); Sajedeh Behnia (NPL, UK); Hannah Cheales (NPL, UK); Jonathan Mittaz (University of Reading, UK); Sylvie Labroue (CLS, France); Pierre Thibaut (CLS, France); Ngan Tran (CLS, France); Craig Donlon (ESA, Netherlands); Robert Cullen (ESA, Netherlands)

Over the past 30 years, extraordinary efforts have been made to provide an accurate record of global and regional mean sea level data from altimetry measurements. The GCOS (2011) requirements of 0.3 mm/yr are currently met over a 20 year period in global mean. The remaining uncertainties in global mean sea level rise estimates are mainly due to the noise with correlation durations below 1 year, to the wet troposphere correction and to the precise orbit determination involving the International Terrestrial Reference Frame (ITRF). At local scales, the main uncertainty contributions are the inter-mission offset corrections, the noise with correlation durations below 1 year and the wet troposphere correction.

New and more stringent uncertainty requirements to measure sea level variations have been established in order to address scientific questions linked to the sea level and Earth’s energy budgets and the attribution to greenhouse gas (Meyssignac et al., Nature Climate Change, 2023). An ambitious but realistic scenario is proposed to reduce the global mean sea level uncertainty budget in the coming decades so that the scientific requirements are met.