Key projections for 2050
Global mean sea level is projected to rise by about 0.3 to 0.6 metres (approximately 1 to 2 feet) by 2050 relative to the year 2000, across mid-range emissions scenarios assessed in the latest major assessments. This continued rise is effectively locked in due to past emissions and ongoing ocean warming, even if sharp cuts to greenhouse gases are achieved today. Higher-end regional contributions are possible where land subsidence combines with local ocean dynamics, meaning some coasts will experience notably more than the global average. The following sections explain the factors driving these numbers, how they vary by region, and what they mean for coastal risk planning.
How we estimate sea level rise
Scientists combine tide gauge records, satellite altimetry since the early 1990s, and climate models to estimate past and future sea level change. They then attribute changes to specific factors: thermal expansion from warming oceans, melting glaciers and ice sheets, and changes in land water storage. Models are evaluated against observations to quantify likely ranges for different emissions and policy scenarios, producing central estimates and uncertainty bounds that are updated as methods and data improve.
Thermal expansion and melting ice
Ocean warming and water volume
As the ocean warms, water expands and raises sea level globally. This thermal expansion has been a dominant contributor over the past few decades and remains significant for near-term rise. The heat content of the upper ocean is slow to respond, so even with rapid emissions cuts, expansion from past warming will continue to influence sea level for years.
Glaciers and ice sheets
Mountain glaciers worldwide are losing mass and contributing consistently to sea level rise. The larger ice sheets in Greenland and Antarctica have also been losing mass at increasing rates, with parts of Antarctica now contributing more than in earlier decades. While ice sheet behaviour in very high-end scenarios remains uncertain, current observations indicate continued mass loss is expected, underpinning the 2050 projections.
Regional variability and hotspots
Sea level rise is not uniform around the globe. Regional differences arise from ocean circulation patterns, shifts in water mass due to gravity and rotation, vertical land motion, and local climate patterns. Some coasts may see rise above the global average, while others may temporarily see less. Subsidence from groundwater extraction, mining, or natural compaction can amplify local risk in cities and deltas.
Notable regional factors
- Coastal regions sinking from groundwater extraction or resource extraction can experience higher relative rise.
- Weakening of major ocean currents, such as the Atlantic Meridional Overturning Circulation, can shift sea level patterns.
- Changes in wind and pressure systems can pile up water in some areas and draw it down in others.
Impacts and planning implications
Even with a central estimate of 0.3 to 0.6 metres by 2050, the likelihood of higher water during storms and high tides increases, affecting flood frequency, coastal infrastructure, and ecosystems. For planners, considering the upper end of the range alongside local subsidence and protection standards is important for robust adaptation. Incremental emissions choices this decade can still influence risk beyond 2050, underscoring the value of mitigation alongside coastal preparedness.
Comparison of factors contributing to sea level rise
| Contributor | Estimated contribution to global mean sea level rise by 2050 (relative to 2000) | Source type |
|---|---|---|
| Thermal expansion | 0.10 to 0.20 metres | Model-based assessment |
| Mountain glaciers | 0.04 to 0.08 metres | Model-based assessment |
| Greenland ice sheet | 0.03 to 0.08 metres | Model-based assessment |
| Antarctic ice sheet | 0.02 to 0.07 metres (with broader uncertainty) | Model-based assessment |
| Land water storage changes | −0.02 to +0.02 metres (small regional effects) | Model-based assessment |
What this means for communities and infrastructure
For coastal communities, roads, ports, and stormwater systems, planning for 2050 sea levels that are measurably higher than today is increasingly essential. Adaptive pathways that combine protection, accommodation, and strategic retreat where necessary can reduce long-term risk. Updated design standards that account for the full range of plausible 2050 conditions help ensure investments remain effective as the ocean continues to rise.
Key uncertainties and research priorities
Important uncertainties remain in how quickly ice sheets will lose mass, particularly in Antarctica, and in the trajectory of global and regional emissions. Continued monitoring, process studies, and improved models narrow these uncertainties over time. Near-term policy and infrastructure decisions can be made with greater confidence when they consider a range of plausible futures rather than a single single estimate.
Summary points
- By 2050, global mean sea level is very likely to rise by roughly 0.3 to 0.6 metres (1–2 feet) relative to year 2000 under mid-range emissions pathways.
- Even with rapid emissions reductions, sea level will continue to rise for decades due to past warming and ocean heat uptake.
- Regional variability can be substantial; local subsidence and ocean dynamics may raise or lower sea level relative to the global average.
- Thermal expansion, melting glaciers, and ice sheet losses are the dominant physical contributors to near-term rise.
- Planning for higher water should combine robust infrastructure, updated design standards, and flexible adaptation pathways to manage long-term risk.