top of page



  • Global mean sea-level rise is a consequence of human-induced climate change. In a warming world, the combined effects of thermal expansion of seawater and melting of the terrestrial cryosphere result in global mean sea level rise [link]. 

  • Global Mean Sea Level (GMSL) rose faster in the 20th century than in any prior century over the last three millennia, with a 0.20 [0.15 to 0.25] m rise over the period 1901–2018. GMSL rise has accelerated since the late 1960s, with an average rate of 2.3 [1.6 to 3.1] mm yr–1 over the period 1971–2018, increasing to 3.7 [3.2 to 4.2] mm yr–1 over the period 2006–2018 [link]. 

  • Observations show that global sea levels have already risen by 0.20±0.05m between 1901 and 2018. The assessed sum of the observed components indicates that GMSL very likely increased by 72 to 117 mm over the period 1971-2018, with the largest contributions from ocean thermal expansion (50%) and melting of ice sheets and glaciers (42%). The assessed total GMSL change for the period 1971-2018 has a very likely range of 73-146 mm, and as a result, the sea-level budget is closed for this period [link].

  • Sea level rise is already impacting ecosystems, human livelihoods, infrastructure, food security and climate mitigation at the coast and beyond. Ultimately, it threatens the existence of cities and settlements in low-lying areas and some island nations and their cultural Heritage[ link].

  • Extreme still water levels ESWL (combining relative sea level, tide and surge) that occurred once per century in the recent past will occur annually or more frequently at about 19–31% of tide gauges by 2050 and at about 60% 6 (SSP1-2.6) to 82% (SSP5-8.5) of tide gauges by 2100 [link].

  • Regional sea level change has been the main driver of changes in extreme still water levels across the quasi-global tide gauge network over the 20th century and will be the main driver of a substantial increase in the frequency of extreme still water levels over the next century [link].

  • Continued and accelerating sea level rise will encroach on coastal settlements and infrastructure and commit low-lying coastal ecosystems to submergence and loss [link].

  • The population potentially exposed to a 100-year coastal flood is projected to increase by about 20% if global mean sea level rises by 0.15 m relative to 2020 levels; this exposed population doubles at a 0.75 m rise in mean sea level and triples at 1.4 m without population change and additional adaptation. 

  • Sea level rise poses an existential threat for some Small Islands and some low-lying coasts [link].

  • By 2100, the value of global assets within the future 1-in-100-year coastal floodplains is projected to be between US$7.9 and US$12.7 trillion (2011 value) under RCP4.5, rising to between US$8.8 and US$14.2 trillion under RCP8.5 [link].

  • Under a high-emissions, low-likelihood/high-impact scenario, where low confidence ice-sheet mass loss occurs, global mean SLR could exceed the likely range by more than one additional meter in 2100 [link].

  • A global two-meter rise of sea level relative to the period 1995-2004 will be exceeded sooner or later within a time window ranging from one century to as long as two millennia, depending on future greenhouse gas emissions and polar ice-sheet melting. While adapting to the most immediate impacts of sea-level rise, such as flooding at high tide and during storms or cyclones, adaptation to multi-meter sea-level rise should start as well to avoid lock-ins in the future [Link].

  • Sea level rise as the result of climate change is likely to influence mangroves in all regions, with a greater impact on North and Central America, Asia, Australia, and East Africa than on West Africa and South America [Link].


Future sea level rise combined with storm surges and heavy rainfall will increase compound flood risks. Unavoidable sea level rise will bring cascading and compounding impacts resulting in losses of coastal ecosystems and ecosystem services, groundwater salinization, flooding and damages to coastal infrastructure that cascade into risks to livelihoods, settlements, health, well-being, food and water security, and cultural values in the near to long-term [link]. When sea levels rise as rapidly as they have been, even a small increase can have devastating effects on coastal habitats farther inland. It can cause destructive erosion, wetland flooding, aquifer and agricultural soil contamination with salt, and lost habitat for fish, birds, and plants. Already, flooding in low-lying coastal areas is forcing people to migrate to higher ground, and millions more are vulnerable to flood risk and other climate change effects. The prospect of higher coastal water levels threatens essential services such as port transport infrastructures since much of the underlying communications infrastructure lies in the path of rising seas [link].

Sea level rise poses a distinctive and severe adaptation challenge as it implies dealing with slow onset changes and increased frequency and magnitude of extreme sea level events, which will escalate in the coming decades. Such adaptation challenges would occur much earlier under high rates of sea level rise, in particular, if low-likelihood, high-impact outcomes associated with collapsing ice sheets occur. Responses to ongoing sea level rise and land subsidence in low-lying coastal cities and settlements, and small islands include protection, accommodation, advance and planned relocation. These responses are more effective if combined and/or sequenced, planned well ahead, aligned with sociocultural values and development priorities, and underpinned by inclusive community engagement processes [link]. Coastal areas are more than just places to live - they are key to our economy and way of life. Marine transportation of goods, offshore energy drilling, seafood cultivation, mineral extraction, tourism, and other coastal activities are integral to the nation's economy, generating more than half of the national gross domestic product (GDP). Coastal cities all over the world are expected to face problems combined with strong hurricanes and storm surges; sea level rise is even more threatening. Coastal cities and settlements play a crucial role in moving toward higher climate-resilient development, given firstly, almost 11% of the global population – 896 million people – lived within the Low Elevation Coastal Zone in 2020, potentially increasing to more than 1 billion people by 2050, and these people, and associated development and coastal ecosystems, face escalating climate compounded risks, including sea level rise [link]. As a result of these risks, many coastal cities are already planning adaptation measures to cope with the long-term prospects of higher sea levels, often at considerable cost. Cities are deploying a broad range of strategies to adapt infrastructure to flooding, with hard engineering approaches (e.g., dikes and seawalls) increasingly complementing soft approaches, including planning and use of nature-based solutions, emphasizing natural and social capital [link].

Coastal impacts of SLR can be avoided by preventing new development in exposed coastal locations. For existing developments, a range of near-term adaptation options exists, including (1) engineered, sediment or ecosystem-based protection; (2) accommodation and land use planning to reduce the vulnerability of people and infrastructure; (3) advance through, e.g., land reclamation; and (4) retreat through planned relocation or displacements and migrations due to SLR [link].

Rising sea levels, as a result of climate change, mean that coasts are eroding at a fast rate, and storm surges are more likely to cause damaging coastal flooding. Natural coastal vegetation, such as saltmarsh and mangrove swamps, can, in the right places, stabilize the shoreline and act as a buffer, absorbing the force of waves. On a natural coast, the shoreline will move inland, and as the sea level rises, the coastal vegetation will gradually move inland with it. This contrasts with hard coastal defenses such as sea walls and banks, which can be overwhelmed and fail. In many places, however, coastal habitats have been cleared, and where there are hard sea defences behind the coastal zone, the vegetation disappears as the coast erodes rather than moving inland. This is often referred to as ‘coastal squeeze’ as the vegetation is squeezed between the sea and the sea wall. Restoring coastal habitats and removing hard sea defences can help reduce the risks of catastrophic flooding [link]. Whether it's protection, accommodation or relocation, coastal adaptation projects take time to put in place, and so does coastal governance to address sea-level rise: often several years and sometimes decades. Coastal adaptation practitioners need to consider these lead times to avoid running out of time when sea-level rise or sea-level rise rates will exceed local coping capacities [link]. 

Coastal adaptation is more efficient when clear objectives are set out, and measures are planned, implemented and evaluated in a sequenced way while ensuring that relevant stakeholders are involved in the decision-making process [link]. While adapting to sea-level rise, coastal communities will need to address other social, economic and environmental challenges. The IPCC defines climate resilient development as “the process of implementing greenhouse gas mitigation and adaptation measures to support sustainable development for all” [link]. In other words, meeting sustainable development goals [link]. Each coastal area is different, but all are confronted with the same domain and the same challenge to find a pathway toward sustainability. To ensure that coastal adaptation benefits all and provides equitable and just outcomes, adaptation should be considered part of the broader challenge to meet sustainable development goals [link]. 



IPCC AR6 Sea Level Projection

The NASA Sea Level Projection Tool allows users to visualize and download the sea level projection data from the IPCC 6th Assessment Report (AR6). The goal of this tool is to provide easy and improved access and visualization to the consensus projections found in the report. The target audience is intended to be broad, allowing a general audience and scientists alike to interact with the information contained in the AR6.


Coastal Future (CoFu)

The Coastal Futures (CoFu) viewer is created and maintained by IHE Delft, The Netherlands (see Team CoFu) through a collaboration between the Department of Coastal and Urban Risk & Resilience and the Department of Hydro informatics and Socio-Technical Innovation. IHE Delft expects that the free, centralized availability of multiple coastal climatic impact-driver projections for different periods and climate scenarios will be of great benefit to many different stakeholders interested in coastal safety, coastal developments, and adaptation.


Climate Central Coastal Risk Screening Tool

An interactive map showing areas threatened by sea level rise and coastal flooding. Combining the most advanced global model of coastal elevations with the latest projections for future flood levels. These interactive maps are developed using  CoastalDEM® v2.1, a near-global digital elevation model for ocean coastal areas. CoastalDEM v2.1 has substantially reduced bias and error scatter even compared to its predecessor, CoastalDEM v1.1, making it the best-performing of all leading, publicly-available, global digital elevation models tested. CoastalDEM v2.1 is the result of substantial new investment, new neural network architecture, and additional and improved input datasets. CoastalDEM v2.1 now predicts corrections on land with elevations between -10 m and 120 m (CoastalDEM v1.1 was 1 - 20 m), making for much broader coverage of coastal areas.


Permanent Service for Mean Sea Level (PSMSL)

PSMSL is the global data bank for long-term sea level change information from tide gauges and bottom pressure recorders. Users can obtain tide gauge data and visualize and explore sea-level trends and anomalies. All data can be freely downloaded.


Data Analysis Tools

The NASA Sea Level Change Data Analysis Tool (DAT) has been designed to allow for quick-look comparisons and analysis of NASA datasets of sea level change. The datasets range from sea level observations to ice observations to model output to quickly study anomalies and get immediate results on potential relations between different datasets. For computational reasons, all data have been interpolated to a 1x1 degree grid. Full data sets can be downloaded through the database for further analysis.

Get to Know AID Members

You can consult with the AID group leader or any members for your regional, national, and global datasets, tools, and analytics projects and questions.


  • Facebook
  • Twitter
  • LinkedIn
  • Instagram


bottom of page