Sea Level Rise Calculator

Sea level rise is the long-term increase in the average height of the world's oceans. It is driven by two main processes: the melting of land-based ice (glaciers, ice caps, and the Greenland and Antarctic ice sheets) which adds water to the ocean, and thermal expansion — the physical property of seawater expanding in volume as it warms. Human-caused greenhouse gas emissions accelerate both processes.

Global mean sea level has risen approximately 20–23 cm (8–9 inches) since 1880, with the rate accelerating significantly in recent decades. Since the early 1990s, satellite altimetry data shows an average rise of about 3.3–3.7 mm per year, and that annual rate has been accelerating at roughly 0.084 mm per year every year.

Thermal expansion refers to the increase in ocean volume as seawater absorbs heat. As the ocean warms, water molecules move faster and occupy more space, raising the sea surface. Thermal expansion currently accounts for approximately 40–50% of observed sea level rise, contributing around 1.4 mm per year and making it the single largest individual contributor.

RCP (Representative Concentration Pathway) scenarios represent different trajectories of greenhouse gas concentrations based on global policy choices. RCP 2.6 assumes aggressive emissions cuts and limiting warming to ~1.5–2°C. RCP 4.5 assumes moderate action, while RCP 8.5 represents a business-as-usual trajectory with roughly 4°C of warming by 2100. Higher RCP scenarios lead to substantially greater ice melt rates and thermal expansion, resulting in much larger sea level projections.

Under low-emission scenarios (RCP 2.6), the IPCC projects a likely global mean sea level rise of 0.3–0.6 m (1–2 feet) by 2100 relative to 1995–2014 levels. Under high-emission scenarios (RCP 8.5), projections reach 0.6–1.1 m (2–3.6 feet) or more, with some studies citing higher-end estimates if Antarctic instability processes accelerate significantly.

Sea level rise is not linear — the annual rate itself is increasing over time due to accelerating ice loss and continued ocean warming. Satellite data shows the rate has been accelerating at approximately 0.084 mm per year squared since the 1990s. Including this acceleration factor provides a more realistic projection than assuming a constant annual rate, especially over longer time horizons.

Global mean sea level rise is the average increase across all oceans. Local (relative) sea level change at any specific coastline can differ substantially due to land subsidence or uplift (vertical land motion), gravitational effects from ice melt, ocean circulation changes, and regional variations in thermal expansion. This calculator estimates global mean sea level rise; local impacts may be higher or lower.

On human timescales, sea level rise is effectively irreversible — even if emissions were halted immediately, thermal expansion and ice melt already committed by current warming would continue for centuries. However, aggressive emissions reductions can significantly slow the rate of rise, avoiding the worst high-end scenarios and giving coastal communities more time to adapt.