Global sea level has risen about 10 cm since 1993 and the rate has roughly doubled, while some 896 million people live in the low-lying coastal zone; proven ways to adapt exist, but early warnings and adaptation finance reach only part of the people and places that need them.
Written from the sources listed below, not independently peer-reviewed.
Around 896 million people live in the world's low-lying coastal zone. Out of every 100 people on Earth, about how many is that?
4.75 mm a year
Average rate of global sea-level rise, 2012–2025
Satellite-based estimate reported by WMO, against 2.65 mm a year over 1993–2011. In 2025 global mean sea level stayed close to the record high of 2024.
Data year 2025. Source: World Meteorological Organization, 2026
About 10 cm
Rise in global mean sea level since 1993
NASA analysis of the satellite record up to 2025. The yearly rate has more than doubled over these three decades.
Data year 2025. Source: NASA Jet Propulsion Laboratory, 2026
896 million
People living in the low-lying coastal zone
IPCC estimate for 2020, nearly 11% of the world's population. Projected to exceed one billion by 2050 under all five socio-economic scenarios assessed.
Data year 2020. Source: Intergovernmental Panel on Climate Change, 2023
Unit: mm per year
IPCC AR6 best estimates of the average yearly rate over three periods, plotted at the final year of each: 1901–1971, 1971–2006 and 2006–2018. Each value has an uncertainty range (for 2006–2018, 3.2 to 4.2 mm a year). WMO reports a later average of 4.75 mm a year for 2012–2025; it comes from a different source and period, so it is not added to this series.
SDG 13 asks countries to strengthen resilience and adaptive capacity to climate-related hazards, and the UN's Early Warnings for All initiative aims to protect every person on Earth with an early warning system by 2027. WMO and UNDRR report that 119 countries, 60% of the total, now have multi-hazard early warning systems, more than double the number ten years earlier, and that disaster mortality is nearly six times lower in countries with comprehensive systems. With only 43% of small island developing states covered and little more than a year left, the 2027 goal is not yet within reach.
Nearly 11% of the world's population lived in the low-lying coastal zone in 2020, and the IPCC expects more than one billion people to live there by 2050 as coastal populations keep growing.
Source: Intergovernmental Panel on Climate Change, 2023Only 43% of small island developing states reported having multi-hazard early warning systems in 2025, compared with 60% of all countries.
Source: World Meteorological Organization and UN Office for Disaster Risk Reduction, 2025Least developed countries have the lowest scores for how complete their early warning systems are, even though those scores have doubled, and Africa remains the lowest-scoring region despite the largest gains since 2015.
Source: World Meteorological Organization and UN Office for Disaster Risk Reduction, 2025UNEP estimates that developing countries will need more than US$310 billion a year for adaptation by 2035, about 12 times the US$26 billion in international public adaptation finance they received in 2023.
Source: United Nations Environment Programme, 2025Each country is shaded by its latest available value, so you can see where the gap is widest. Hover or tap a country, search for one, or open the full table.
Loading country values…
Share of each country's population living in areas 5 metres or less above sea level, from CIESIN's Low Elevation Coastal Zone estimates. All values refer to 2015 (the latest year in the dataset) and do not show whether people are protected by dikes or other defences, as in the Netherlands. Values for flat deltas, atolls and small islands rest on coarse elevation data and should be read with caution.
Source: CIESIN (Columbia University) and CUNY CIDR, via World Bank Open Data. Latest year available per country; years differ.
Values load from World Bank Open Data. Simplified Natural Earth borders; they imply no position on disputed territories.
Instead of one “percent solved” score, DO GOOD rates three separate dimensions. A problem can have mature solutions that still reach too few people. These ratings are an editorial reading of the sources on this page, not a measured index.
Has the situation improved in the real world?
LowThe sea keeps rising and the rate has roughly doubled since the 1990s, to 4.75 mm a year over 2012–2025, while the number of people living in the low-lying coastal zone is growing toward one billion.
How mature and validated are the available solutions?
ModerateProtection, accommodation, nature-based defences, early warning and planned relocation are well understood, but the IPCC warns that beyond 2050 the adjustments needed in some places may exceed the limits of current adaptation options.
How widely are effective solutions actually used?
LowOnly 43% of small island developing states report multi-hazard early warning systems, and international public adaptation finance for developing countries was US$26 billion in 2023 against needs of more than US$310 billion a year by 2035.
Global sea level is measured precisely by satellites and the IPCC assesses the observed rise with high confidence. Local rise, land subsidence, how many people are exposed and how well defences protect them are much less certain, and high-end projections linked to ice-sheet instability carry low confidence.
The rate of rise is accelerating and international public adaptation finance fell from US$28 billion in 2022 to US$26 billion in 2023. Early warning coverage is improving, which reduces deaths but does not slow the loss of land.
The sea is rising because ocean water expands as it warms and because glaciers and the Greenland and Antarctic ice sheets are losing ice. The IPCC finds that global mean sea level rose by about 20 cm between 1901 and 2018, faster since 1900 than in any century of at least the last 3,000 years. The rise is speeding up: WMO reports an average of 4.75 mm a year over 2012–2025, against 2.65 mm a year over 1993–2011, and NASA calculates that the sea now stands about 10 cm higher than when satellite measurements began in 1993. Individual years vary with natural cycles. In 2025, La Niña shifted rain from the oceans onto land and the rise was only 0.08 cm, against 0.59 cm in 2024, but the long-term rate is still accelerating.
Higher seas make storm surges and high-tide floods reach further inland, wear away coastlines and push salt water into soils and groundwater. The IPCC estimates that around 896 million people, nearly 11% of the world's population, lived in the low-lying coastal zone in 2020, and expects that number to exceed one billion by 2050 in every scenario it assessed. IPCC projections show the sea still rising in 2300 under every emissions scenario, so the question is not whether coasts must adapt but how fast. Small island developing states and low-lying deltas face the sharpest choices, often with the least money and data: only 43% of small island developing states report having multi-hazard early warning systems, and international public finance for adaptation in developing countries is a fraction of what UNEP estimates they need.
Sea-level rise is tracked with tide gauges and satellites, and exposure by combining elevation maps with population data. The main measures are:
Global mean sea level
The average height of the ocean surface. Before the 1990s it is reconstructed from tide gauges; since 1993 a series of satellite altimeters, currently led by the Sentinel-6 Michael Freilich mission, measures it directly. Gravity satellites and Argo ocean probes help separate the share from added water (melting ice) from the share from warming water.
Rate of rise and acceleration
Changes are reported as average millimetres per year over a period, because single years swing with El Niño and La Niña. Comparing periods shows whether the rise is speeding up: IPCC rates increased from 1.3 mm a year in 1901–1971 to 3.7 mm a year in 2006–2018.
Relative sea level at the coast
What matters for a given place is the sea level relative to the land, which also depends on whether the ground is sinking or rising and on local ocean currents. Global averages therefore do not tell any single coastal city how much its sea will rise.
People in low-lying coastal areas
Exposure is estimated by overlaying population maps on digital elevation models. Results depend on the elevation threshold (for example 5 m or 10 m) and on the quality of the elevation data, which is weakest for flat deltas and small islands, and they do not show whether people are protected by dikes or other defences.
What works
Forecasts, warnings that reach people in time, and evacuation plans save lives when high tides and storms push the sea inland. WMO and UNDRR report that disaster mortality is nearly six times lower in countries with comprehensive multi-hazard early warning systems than in those with limited capabilities.
Limits
Warnings protect people but not land, homes or freshwater, and only 43% of small island developing states report having such systems. Funding often does not cover the long-term operation and maintenance that systems need.
What works
Mangroves, salt marshes, coral reefs, seagrass and dunes reduce wave energy and erosion, can build up sediment as the sea rises and support fisheries at the same time. Where there is room for them, protecting and restoring them can complement or partly replace hard structures.
Limits
They need space and time to grow, can be overwhelmed if the sea rises too fast or warming kills corals, and on their own rarely protect dense cities against large storm surges.
What works
Hard defences can protect dense cities, ports and farmland for decades and are well proven in low-lying countries that maintain them.
Limits
They are expensive to build and maintain, can shift erosion to neighbouring coasts and create a false sense of safety. The IPCC notes that faster sea-level rise shortens the useful lifetime of such measures and calls for earlier and stronger responses.
What works
Raising buildings and critical infrastructure, flood-proofing, updating building codes and keeping new development out of the most exposed areas reduce damage without fully holding back the sea.
Limits
Rules are only as good as their enforcement, often apply only to new buildings, and depend on local elevation and flood maps that many developing countries lack.
What works
Moving homes, services and sometimes whole communities away from the most exposed shores, with time to plan and with the people affected involved in decisions, can permanently remove risk where protection is not affordable or possible.
Limits
Relocation is costly and can break ties to land, livelihoods and culture, and it is hardest for low-lying atoll nations with little high ground. The IPCC warns that beyond 2050, some locations may need adjustments beyond the limits of current adaptation options.
Promising, but not proven at scale. The stage shows how far each approach has come; it is not a recommendation.
Instead of one fixed design, coastal plans set out a sequence of measures with trigger points for switching from one to the next as the sea rises, which helps when the lifetime of a defence is uncertain. The approach is used in some large deltas and cities, but needs long-term institutions and monitoring that many places do not have.
Combining restored mangroves, marshes or reefs with lower dikes or breakwaters aims to get the reliability of engineering and the self-repairing, cheaper qualities of ecosystems. Evidence on how such hybrids perform in large storms and over decades is still limited.
Some low-lying island states and cities are building new land or raising existing land above projected sea levels, and testing elevated or floating buildings. These options are expensive, can damage reefs and lagoons, and their long-term costs and benefits are not well studied.
Scientists are improving models and observations of Antarctic and Greenland ice to narrow the high-end range of future rise. The IPCC treats a storyline involving ice-sheet instability as low-likelihood but high-impact because confidence is still low.
Implementation gap
Developing countries' adaptation finance needs are estimated at more than US$310 billion a year by 2035, while international public adaptation finance was US$26 billion in 2023 and the goal of doubling it to about US$40 billion by 2025 is not on track.
Implementation gap
Only 43% of small island developing states report multi-hazard early warning systems, and least developed countries have the least complete systems. A digital divide limits the reach of newer tools.
Coordination gap
Coastal measures take years to plan and build and are meant to last decades. The IPCC notes that faster rise demands earlier, stronger action and shortens the lifetime of measures, so decisions delayed now narrow future options.
Knowledge gap
Projections for 2100 range from 0.28–0.55 m under very low emissions to 0.63–1.01 m under very high emissions (relative to 1995–2014), and a possible faster ice-sheet collapse is not captured in these ranges, which makes it hard to size defences for long-lived infrastructure.
Technology gap
Freely available elevation models are least accurate in flat deltas and on small islands, and many coastal cities do not measure how fast their ground is sinking, so local flood risk is often underestimated or unknown.
Coordination gap
Managed retreat involves land ownership, compensation, cultural ties and, for atoll nations, questions about territory and citizenship that no single agency or country can settle alone.
Unresolved questions, not vetted breakthroughs. Answering any of them would change what is possible.
Which processes could make the Antarctic and Greenland ice sheets lose ice much faster this century, and how likely is a rise well above the IPCC's likely range by 2100 and 2150?
At what rates of rise can mangroves, marshes and reefs keep building upward, and how well do they protect people during major storms compared with hard defences?
What financing, land arrangements and decision processes allow communities to move on their own terms, and how can people who move keep their rights, livelihoods and culture?
How will maritime boundaries, statehood and citizenship be treated if low-lying island states lose much of their habitable land, and what international arrangements would protect their people?
If you live near a coast or tidal river, check official flood maps and warning services for your area, sign up for alerts and know your evacuation route.
Coastal defences, building rules and decisions about new development are usually made locally. Commenting on plans and supporting the protection of dunes, wetlands and mangroves can shape how your area adapts.
Back groups that restore coastal ecosystems, run community early warning and preparedness programmes, or support island and delta communities in planning their own adaptation.
Every increment of warming adds to long-term sea-level rise, so reducing energy use and supporting a shift to clean energy limits how much adaptation will be needed in the future.
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World Meteorological Organization (March 2026), published 2026
WMO's summary of its State of the Global Climate 2025 report (released 23 March 2026). Source of the average rate of 4.75 mm a year over 2012–2025 against 2.65 mm a year over 1993–2011, and of sea level in 2025 remaining near the 2024 record.
NASA Jet Propulsion Laboratory (29 January 2026), published 2026
NASA's annual analysis of the satellite sea-level record. Source of the rise of about 10 cm since 1993, the more than doubled yearly rate, the rise of 0.08 cm in 2025 (against an expected 0.44 cm) and 0.59 cm in 2024, the role of La Niña, and the satellites and probes used.
Intergovernmental Panel on Climate Change (2023), published 2023
IPCC Sixth Assessment Report synthesis, the latest full assessment (AR7 is due later in the decade). Source of the 896 million people in the low-lying coastal zone (nearly 11% of the 2020 population), the projected rise above one billion by 2050, sea-level projections for 2100, the low-likelihood ice-sheet storyline, the shorter lifetime of measures under faster rise and possible limits of adaptation beyond 2050.
Intergovernmental Panel on Climate Change, Working Group I (2021), published 2021
IPCC AR6 Working Group I assessment of observed change. Source of the 0.20 m rise between 1901 and 2018, the average rates for 1901–1971, 1971–2006 and 2006–2018 used in the trend, and the finding that sea level has risen faster since 1900 than in any century of at least the last 3,000 years (paragraphs A.1.7 and A.2.4).
United Nations Environment Programme (29 October 2025), published 2025
UNEP's annual assessment of adaptation progress and finance. Source of developing countries' adaptation finance needs of more than US$310 billion a year by 2035, international public adaptation finance of US$26 billion in 2023 (US$28 billion in 2022), the 12-fold gap and the Glasgow doubling goal.
World Meteorological Organization and UN Office for Disaster Risk Reduction (12 November 2025), published 2025
Release of the 2025 global status report tracking Sendai Framework Target G. Source of the 119 countries (60%) with multi-hazard early warning systems, the 113% increase over ten years, the 43% of small island developing states, regional and least developed country scores, the nearly six times lower disaster mortality and the Early Warnings for All 2027 goal.
DO GOOD International (2026). Adapting to Sea-Level Rise. Global Challenges. Updated October 15, 2026. https://www.dogood.world/challenges/sea-level-rise
For figures, please cite the original sources listed above.