Sea level rise

Managed retreat, accommodating coastal change, or protecting against sea level rise through hard-construction practices like seawalls[18] are hard approaches.

[35][39][40] This theory had been highly influential – in a 2020 survey of 106 experts, the 2016 paper which suggested 1 m (3+1⁄2 ft) or more of sea level rise by 2100 from Antarctica alone,[26] was considered even more important than the 2014 IPCC Fifth Assessment Report.

[42] Marine ice cliff instability had also been very controversial, since it was proposed as a modelling exercise,[37] and the observational evidence from both the past and the present is very limited and ambiguous.

[44] So far, only one episode of seabed gouging by ice from the Younger Dryas period appears truly consistent with this theory,[45] but it had lasted for an estimated 900 years,[45] so it is unclear if it supports rapid sea level rise in the present.

[47][48][49][43] Due to these uncertainties, some scientists – including the originators of the hypothesis, Robert DeConto and David Pollard – have suggested that the best way to resolve the question would be to precisely determine sea level rise during the Last Interglacial.

In the worst estimated scenario, SSP-8.5 with ice cliff instability, the projected range for total sea level rise was 9.5–16.2 metres (31–53 ft) by the year 2300.

(Negative values represent the extremely low probability of large climate change-induced increases in precipitation greatly elevating ice sheet surface mass balance.

Continued carbon dioxide emissions from fossil fuel sources could cause additional tens of metres of sea level rise, over the next millennia.

[59] Burning of all fossil fuels on Earth is sufficient to melt the entire Antarctic ice sheet, causing about 58 m (190 ft) of sea level rise.

Over a consistent time period, assessments can attribute contributions to sea level rise and provide early indications of change in trajectory.

)[72] By 2018, data collected by Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) had shown that the global mean sea level was rising by 3.2 mm (1⁄8 in) per year.

In the recent geological past, thermal expansion from increased temperatures and changes in land ice are the dominant reasons of sea level rise.

Other factors affecting sea level rise include changes in snow mass, and flow from terrestrial water storage, though the contribution from these is thought to be small.

[35] Their disappearance would take at least several centuries, but is considered almost inevitable, as their bedrock topography deepens inland and becomes more vulnerable to meltwater, in what is known as marine ice sheet instability.

[84][85] Once ice loss from the West Antarctica is triggered, the only way to restore it to near-present values is by lowering the global temperature to 1 °C (1.8 °F) below the preindustrial level.

[108] Other researchers suggested that a climate engineering intervention to stabilize the ice sheet's glaciers may delay its loss by centuries and give more time to adapt.

One way to do this in theory would be large-scale carbon dioxide removal, but there would still be cause of greater ice losses and sea level rise from Greenland than if the threshold was not breached in the first place.

[141] Observational and modelling studies of mass loss from glaciers and ice caps show they contribute 0.2–0.4 mm per year to sea level rise, averaged over the 20th century.

United Nations Secretary-General António Guterres warned in 2023 that sea level rise risks causing human migrations on a "biblical scale".

[161][162] Starting around 2050, some nesting sites in Florida, Cuba, Ecuador and the island of Sint Eustatius for leatherback, loggerhead, hawksbill, green and olive ridley turtles are expected to be flooded.

[168][169][170][171] Both mangroves and tidal marshes protect against storm surges, waves and tsunamis, so their loss makes the effects of sea level rise worse.

[178] Scientists have linked extreme regional sea level rise on the US Northeast Coast to the downturn of the Atlantic meridional overturning circulation (AMOC).

[188][189] Some experts argue that retreat from the coast would have a lower impact on the GDP of India and Southeast Asia then attempting to protect every coastline, in the case of very high sea level rise.

[158] Across sub-Saharan Africa as a whole, damage from sea level rise could reach 2–4% of GDP by 2050, although this depends on the extent of future economic growth and climate change adaptation.

Bangladesh, China, India, Indonesia, Japan, Pakistan, the Philippines, Thailand and Vietnam alone account for 70% of people exposed to sea level rise during the 21st century.

Nine of these are the so-called sinking cities, where subsidence (typically caused by unsustainable groundwater extraction in the past) would compound sea level rise.

Because of its complex geography, the authorities chose a flexible mix of hard and soft measures to cope with sea level rise of over 1 meter per century.

In Mexico, damage from SLR to tourism hotspots like Cancun, Isla Mujeres, Playa del Carmen, Puerto Morelos and Cozumel could amount to US$1.4–2.3 billion.

[228][229] Five of the Solomon Islands have already disappeared due to the effects of sea level rise and stronger trade winds pushing water into the Western Pacific.

[230] Adaptation to sea level rise is costly for small island nations as a large portion of their population lives in areas that are at risk.

The global average sea level has risen about 25 centimetres (9.8 in) since 1880. [ 1 ]
Sea surface height change from 1992 to 2019: Blue regions are where sea level has gone down, and orange/red regions are where sea level has risen (the visualization is based on satellite data). [ 2 ]
A graph showing ice loss sea ice, ice shelves and land ice. Land ice loss contributes to SLR
Earth lost 28 trillion tonnes of ice between 1994 and 2017: ice sheets and glaciers raised the global sea level by 34.6 ± 3.1 mm. The rate of ice loss has risen by 57% since the 1990s − from 0.8 to 1.2 trillion tonnes per year. [ 20 ]
Sea level rise for the low-emission, high-emission (RCP 8.5, lower left) and in-between scenarios according to the different approaches. Projections are very similar for low warming, but disagreement increases alongside the temperature [ 23 ]
Historical sea level reconstruction and projections up to 2100 published in 2017 by the U.S. Global Change Research Program . [ 28 ] RCPs are different scenarios for future concentrations of greenhouse gases.
For the 2021 IPCC report, three steps were taken to present a wider picture than the previous report (top left): state-of-the-art ice sheet model projections from 2020 (lower left), research modeling the possibility of ice cliff instability (upper right) and combined expert projections of sea level rise from Greenland and Antarctica (lower right) were all considered before settling on the projections. Note that projections on the right use a larger scale, which ends at 2.5 m ( 8 + 1 ⁄ 3 ft) instead of 1.5 m (5 ft) [ 29 ]
The stages of marine ice sheet (top) and marine ice cliff (bottom) instabilities. Dashed lines show that the retreat would be much more rapid if ice cliff instability were applicable [ 37 ]
If MICI can occur, the structure of the glacier embayment (viewed from the top) would do a lot to determine how quickly it may proceed [ 43 ]
If countries cut greenhouse gas emissions significantly (lowest trace), sea level rise by 2100 will be limited to 0.3 to 0.6 meters (1–2 feet). [ 52 ] However, in a worst-case scenario (top trace), sea levels could rise 5 meters (16 feet) by the year 2300. [ 52 ]
A map showing major SLR impact in south-east Asia, Northern Europe and the East Coast of the US
Map of the Earth with a long-term 6-metre (20 ft) sea level rise represented in red (uniform distribution, actual sea level rise will vary regionally and local adaptation measures will also have an effect on local sea levels).
Jason-1 continued the sea surface measurements started by TOPEX/Poseidon. It was followed by the Ocean Surface Topography Mission on Jason-2 , and by Jason-3 .
Between 1993 and 2018, the mean sea level has risen across most of the world ocean (blue colors). [ 68 ]
Changes in sea levels since the end of the last glacial episode
The main contributors to sea level rise, and how much they are expected to add by the end of the century under the low-emission scenario ("SSP1-2.6") and the high-emission scenario ("SSP5-8.5"). The Antarctic ice sheet is the least certain contributor [ 29 ]
There has been an increase in ocean heat content during recent decades as the oceans absorb most of the excess heat created by human-induced global warming . [ 86 ]
Processes around an Antarctic ice shelf
The Ross Ice Shelf is Antarctica's largest. It is about the size of France and up to several hundred metres thick.
Aerial view of ice flows at Denman Glacier, one of the less stable glaciers in the East Antarctica
Thwaites Glacier, with its vulnerable bedrock topography visible.
A graphical representation of how warm waters, and the Marine Ice Sheet Instability and Marine Ice Cliff Instability processes are affecting the West Antarctic Ice Sheet
Trends of Greenland ice loss between 2002 and 2019 [ 124 ]
2023 projections of how much the Greenland ice sheet may shrink from its present extent by the year 2300 under the worst possible climate change scenario (upper half) and of how much faster its remaining ice will be flowing in that case (lower half) [ 129 ]
Based on national pledges to reduce greenhouse gas emissions, global mean temperature is projected to increase by 2.7 °C (4.9 °F), which would cause loss of about half of Earth's glaciers by 2100—causing a sea level rise of 115±40 millimeters. [ 139 ]
Trends in land water storage from GRACE observations in gigatons per year, April 2002 to November 2014 (glaciers and ice sheets are excluded).
Major cities threatened by sea level rise of 49 cm ( 1 + 1 ⁄ 2 ft) compared to the level in 2010.
Bramble Cay melomys , the first known mammal species to go extinct due to sea level rise.
An example of mangrove pneumatophores
Sea level rise in many locations across the world is worsened due to land subsidence. The East Coast of the United States is one example. [ 176 ]
Oosterscheldekering , the largest barrier of the Dutch Delta Works .
Planning for the future sea level rise used in the United Kingdom . [ 191 ]
A man looking out over the beach from a building destroyed by high tides in Chorkor , a suburb of Accra . Sunny day flooding caused by sea level rise, increases coastal erosion that destroys housing, infrastructure and natural ecosystems. A number of communities in Coastal Ghana are already experiencing the changing tides.
Matsukawaura Lagoon , located in Fukushima Prefecture of Honshu Island
2010 estimates of population exposure to sea level rise in Bangladesh
King's Beach at Caloundra
An aerial view of São Paulo 's Port of Santos
Beach nourishment in progress in Barcelona .
Tidal flooding in Miami during a king tide (October 17, 2016). The risk of tidal flooding increases with sea level rise.
A comparison of SLR in six parts of the US. The Gulf Coast and East Coast see the most SLR, whereas the West Coast the least
NOAA predicts different levels of sea level rise through 2050 for several US coastlines. [ 14 ]
Malé , the capital island of Maldives .
Surface area change of islands in the Central Pacific and Solomon Islands [ 231 ]