Among the many effects that climate change are having on our planet, the rise in sea levels is probably the most alarming for some nations ― because it means they could no longer exist.
Much of the Indian Ocean archipelago of the Maldives, for example, stands just a few feet above sea level and so is predicted to disappear under the waves this century.
"The most significant impact of climate change will be sea-level rises," Dr Nasser Karami, a climate change researcher in Norway, said. "It will destroy island countries in the Pacific Ocean, the Indian Ocean or other places."
Larger and richer nations may not face an existential crisis, but they are far from immune to the effects of sea-level rises.
UN figures show that about 40 per cent of the world's population live within 100 kilometres of a coast, so significant numbers of people could see their lives upended.
Major coastal cities such as New York may face significant challenges, Dr Karami said. Simulations by the advocacy group the Union of Concerned Scientists indicate that much of the US’s eastern seaboard could suffer dozens of flooding events per year as soon as 2035, even without accounting for storm surges.
Sea levels to rise faster now than in past decades
With warmer temperatures causing the sea to expand and glaciers and ice sheets to melt, the world's seas have risen by an average of more than 20 centimetres since the late 19th century.
A report released in February by the US National Oceanic and Atmospheric Administration and other American government agencies forecast that, from now until 2050, seas will rise a further 10 to 12 inches (25 to 30 centimetres) — more than they have risen over the previous century.
By the mid-century, moderate flooding, which causes disruption and damage to infrastructure, is likely to happen 10 times as often as it does now.
Aside from the effects on coastal communities, there will be consequences for agricultural areas and underground aquifers, which may become contaminated with salt. Wildlife will suffer when natural environments become flooded.
Rises in sea levels are accompanied by increases in the frequency of typhoons, hurricanes and other extreme events, causing storm surges with the potential to devastate coastal communities.
Aftermath of Cyclone Shaheen in Oman – in pictures
Richard Crowther, head of maritime at WSP Middle East, an engineering consultancy that advises on coastal developments, said more extreme weather events were already being seen in the Gulf of Oman and the Indian Ocean.
Modelling WSP carried out with Oman’s Sohar International Port Company and Deltares, another consultancy, suggests that recent cyclones such as Gonu (in 2007) and Kyarr (in 2019) were more severe than would be expected once every century.
"This, therefore, indicated that the estimated return periods for predicted weather events were overestimated, with high magnitude events seemingly occurring more frequently," Mr Crowther said.
Problems are set to intensify, because even under low emissions scenarios, sea levels will continue to rise.
The US National Oceanic and Atmospheric Administration's 2022 Sea Level Rise Technical Report found that at least two feet (0.61 metres) of increase are likely along the US coastline by 2100 because of emissions released until now.
"Failing to curb emissions could cause an additional 1.5 to five feet of rise, for a total of 3.5 to seven feet by the end of this century," the report summary stated.
GCC’s Catch-22: conservative estimates to build coastal properties
A 2021 report of the Intergovernmental Panel on Climate Change warned that global mean sea levels could rise by two metres if greenhouse gas emissions continued at a high rate.
"This presents a Catch-22 for the GCC region as many coastal developments are currently designed using appropriately conservative considerations, which project around one metre of sea-level rise in the next 100 years," Mr Crowther said.
The vulnerability of infrastructure and populations to sea-level rises varies greatly, said Fawzi Dibis, WSP Middle East’s manager for sustainability and climate change. This stems from differences in geography, altitudes and economic models.
"The World Bank highlights that low-lying coastal areas in Tunisia, Qatar, Libya, the UAE, Kuwait and particularly Egypt are at risk," he said.
Areas that will be affected by 1m sea level rise, according to modelling by Climate Central:
The Nile Delta, for example, will face increasing erosion rates; inundation of wetlands and other low-lying areas; increased flooding; faster retreat of the coastline, including erosion of sand dunes and the coastal sand belt; the breaching of coastal barriers; and damage of coastal inlets.
"This would impact the livelihood of huge population centres in Egypt and pose threats to food security, as most agricultural production occurs in the Nile Delta," Mr Dibis said. He added that creating sand dunes and dykes, and preserving existing wetlands, could reduce the risks.
Given that increasing numbers of people and assets could be at risk, Mr Crowther said it was "crucial to ensure that the formation levels of urban developments on coastal areas are raised".
He said investing early in a project to ensure it is able to cope with the stresses of climate change could reduce risks and costs and "ensure fewer stranded assets".
Some projects do take into account the potential for significant sea-level rises, and protection for developments can be unobtrusive and have the potential to be strengthened over time.
Mr Crowther cited as an example WSP’s work on the Marine Life Institute, part of a development called Amaala on the north-west coast of Saudi Arabia.
"We designed partitions for a unique sea wall around the perimeter, which is purposefully designed to take into account sea-level rise and waves by mitigating the exchange of water from one side to the other, all whilst limiting the visual impact," he said.
"By designing this unique feature with an upgradable approach, the acrylic screen partition can be modified in height as sea levels rise over time to preserve both the visual impact of the structure, as well as extend the lifespan of the overall asset."
Coral bleaching and higher salinity
A sea-level rise is far from the only effect climate change is having on seas and oceans. Coral reef bleaching, in which heat stress causes coral to expel the algae that are essential for their functioning, is another consequence, as is harm to fish numbers from high temperatures.
When it comes to temperature increases, the Arabian Gulf is likely to be one of the most heavily affected seas in the world. The Intergovernmental Panel on Climate Change is forecasting a 4.26°C increase in surface temperature between 2010 and 2039.
"Algal blooms and dead zone areas are likely to grow as increases in temperature lead to increased stratification of oxygenated water and concentrate pollutants, thus negatively impacting coastal tourism," Mr Dibis said.
"Additionally, increased evaporation has been linked to an increase in salinity of seawater, which may disrupt marine ecosystems. This could evolve to the potential demise of mangroves and other species."
Higher salinity could also affect desalination plants, power stations and other infrastructure, something that operators will have to consider.
"It’s essential to embed systematic risk management frameworks, adaptation and resilience strategies, and an accelerated pathway to decarbonisation," Mr Dibis said.