What is sea level rise?
Sea levels will rise by 30 centimetres by 2050, regardless of how much we are able to reduce global carbon emissions. Why is this happening and what can we do to adapt?
Families in Kiribati are often forced to live in marginal areas, where flooding caused by high tides increases. Photo by Kennedy Warne
While humans continue to emit greenhouse gases into the atmosphere, the sea has buffered the effects. The world's seas and oceans have absorbed more than 90 per cent of the heat from these gases, but the oceans are suffering the consequences: a new record for ocean warming was set in 2021.
Sea level rise is one of the effects of climate change and global warming. On average, sea levels have risen by about 23 centimetres since 1880, and almost half of these centimetres have risen in the last 25 years. Every year, the sea rises another 3.4 millimetres. A new study published on 15 February 2022 shows that the rate of sea level rise is accelerating and is expected to rise by 30 centimetres by 2050 in the United States.
This implies that in the next 30 years sea levels will rise as much as they have in the last century, the US National Oceanic and Atmospheric Administration (NOAA) says in its latest technical data, which updates 2017 predictions with more accurate estimates.
NOAA Administrator Rick Spinrad called the findings "historic" and warned that sea level rise will happen no matter what, even with a drastic cut in carbon emissions. In the United States, the most vulnerable populations live along the East and Gulf coasts, where flooding is projected to be 10 times more frequent in 2050 than it is now.
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Sea level rise is linked to three factors, all caused by this persistent global climate change:
Thermal expansion: when water warms it expands. About half of the sea level rise of the last century is attributed to the warming of the oceans, whichcaused them to take up more space.
2. Shrinking glaciers and ice caps: Every summer, large ice formations, such as glaciers and ice caps, gradually melt naturally. Normally precipitation in the form of snow, usually from seawater, is sufficient to balance the liquefaction. However, persistent high temperatures caused by climate change have led to more ice melting than usual in summer, in addition to the decrease in snowfall due to late winters and early springs. This imbalance leads to an increase in water runoff into the oceans, causing sea levels to rise.
3. The loss of ice from Greenland and West Antarctica: As with glaciers and ice caps, rising temperatures are causing the huge glacial mounds that cover Greenland and West Antarctica to melt by leaps and bounds. Scientists believe that surface melt and inland seawater are seeping under the mounds, creating ice streams that are moving very fast towards the sea. Rising sea temperatures are causing the huge ice shelves coming out of Antarctica to melt underneath, become brittle and eventually break up.
When sea levels rise as fast as they have been, even the smallest rise can have terrible consequences for people living on the coast. As seawater moves inland, it can lead to soil erosion, flooding of wetlands, contamination of agricultural land and aquifers, and thus loss of habitat for fish, birds and plants.
(Related: Sinking land and rising sea levels: the twin crises facing coastal communities)
Rising sea levels coincide with more dangerous typhoons and hurricanes, as they move slower and leave more rainfall, contributing to more powerful storm surges that can wipe out everything in their path. One study found that between 1963 and 2012, nearly half of the deaths caused by Atlantic hurricanes were caused by storm surges.
Flooding on low-lying coasts is already forcing people to migrate to higher ground and millions are threatened by flood risks and other effects of climate change. Forecasts of a receding coastline threaten basic services such as internet access, as many of the underground telecommunications infrastructures are in the path of rising sea levels.
Adapting to the threat
As a result of these risks, many coastal cities are already planning adaptation measures to cope with long-term forecasts of higher sea levels, usually at considerable cost. Building seawalls, redesigning roads and planting mangroves or other water-absorbing vegetation are options already underway.
In Jakarta (Indonesia), a project costing more than 35 billion euros aims to protect the city with an almost 25-metre high sea wall. Rotterdam (Netherlands), where the Global Adaptation Centre is based, has offered other cities a model for combating flooding and land loss. The Dutch city has built barriers, drains and innovative architectural structures, such as a "water square" with temporary ponds.
Of course, the options for communities vulnerable to sea-level rise are limited in the face of rising seas. In the Marshall Islands, where sea-level rise is forcing a choice between moving or raising land levels, residents will need help from other countries if they choose to take the latter option. Climate 101: GlaciersGlaciers are present on almost every continent. However, they are melting at a rapid rate due to warming. Find out how glaciers are formed and other interesting facts about them.
How much will sea levels rise?
Most predictions say that the planet will continue to warm and possibly at a faster rate, causing sea levels to continue to rise. This means that hundreds of coastal cities will have to cope with flooding. But predicting how much and how fast the seas will rise is still being studied.
The most recent Intergovernmental Panel on Climate Change (IPCC) special report states that we can expect the oceans to rise by 26 to 77 centimetres by 2100 with temperatures rising by more than 1.5°C. This would be enough to seriously affect many cities along the east coast of the United States. This would be enough to seriously affect many of the cities along the east coast of the United States. Another analysis based on European and NASA data leans towards the upper end of that range, predicting a 65 centimetre rise by the end of this century if current inertia continues.
(Related: Sea level rise accelerates: climate change is coming sooner and stronger than expected)
If all the ice that currently exists in glaciers and ice sheets melted, it would raise sea levels by 65 metres, which could cause entire states and even countries to disappear under water, from Florida to Bangladesh. This scenario is not something scientists think likely, and would probably span many centuries, but it could happen if the world continues to burn fossil fuels indiscriminately.
In the meantime, scientists continue to refine their scientific models for studying sea level change and point out that we will see a more or less significant impact on the speed of sea level rise depending on the extent to which all countries work together to limit the emission of more greenhouse gases.
Many people think of global warming and climate change as synonyms, but scientists prefer to use the term "climate change" when describing the complex changes that are already affecting our planet's weather and climate systems.