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Tuesday, August 04, 2020

Explained: How sea level rise could impact millions of people, cost billions of dollars

In a new study, researchers have noted that sea-level rise (SLR) is a "well accepted" consequence of climate change. What are the findings of their study?

By: Explained Desk | New Delhi | Updated: August 1, 2020 10:49:16 am
sea level rise, climate change, impact of climate change, coastal flooding, cost of coastal flooding, indian express Fisher boats off Worli village in Mumbai. (Express Photo: Ganesh Shirsekar)

In a study published Thursday in the journal Scientific Reports, researchers predict that by 2100, the global population potentially exposed to episodic coastal flooding will increase from 128-171 million to 176-287 million. The value of global assets exposed to these episodes is projected to be between $6,000-$9,000 billion, or 12-20 per cent of the global GDP.

What are the findings of the study?

The researchers note that sea-level rise (SLR) is a “well accepted” consequence of climate change. Their study has found that globally, of the 68 per cent area that is prone to coastal flooding, over 32 per cent can be attributed to regional SLR. This, they say, will significantly increase coastal flooding by 2100.

What is regional SLR?

Because sea level rise is not uniform across the world, there is a need to differentiate regional SLR from the global rates. For instance, the gravitational pull of the polar ice sheets has different effects on sea levels in different parts of the world, which means regional SLR can be higher or lower than the global SLR. Relatively too, regional SLR can be higher or lower. For instance, according to an article published in Yale Environment 360, SLR in places such as Scotland, Iceland and Alaska could be significantly less than the regional SLR for eastern US.

Their results indicate by the year 2100, for most of the world, flooding incidents that are typically associated with a 1 in a 100-year event could occur as frequently as 1 in 10 years, “primarily as a result of sea level rise.”

As per this assessment, 0.5-0.7 per cent of the world’s land area is at a risk of episodic coastal flooding by 2100, impacting 2.5-4.1 per cent of the population, assuming there are no coastal defenses or adaptation measures in place.

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How much of a threat is sea level rise?

Last year in September, Indonesia’s President Joko Widodo announced that the country’s capital would be relocated from Jakarta to the province of East Kalimantan on the lesser populated island of Borneo. The relocation was meant to reduce the burden on Jakarta, which has been facing problems such as poor quality air and traffic gridlocks, and is particularly prone to flooding. It is also the largest Indonesian city with a population of 1 crore. It is located on the North West coast of the most populous island in the world, Java. The combination of climate change and heavy congestion continues to bury Jakarta, the “world’s fastest-sinking city”, by about 25 cm into the ground every year.

The situation looks grim for India’s financial capital Mumbai as well. As per some projections, climate change is expected to inundate significant sections of Mumbai by 2050, impacting millions of people.

Other cities that regularly feature in the lists endangered by climate change include Guangzhou, Jakarta, Miami, and Manila.

IPCC projections too maintain that SLR is going to accelerate further and faster in the coming years. Some of the expected impacts of SLR over the course of the century include habitat contraction, loss of functionality and biodiversity and lateral and inland migration.

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What are some ways of protecting against sea level rise?

Indonesia’s government launched a coastal development project called a Giant Sea Wall or “Giant Garuda” (Garuda is the name of a bird from Hindu mythology and is Indonesia’s national symbol) in 2014 meant to protect the city from floods.

In a paper that was accepted for publication earlier this year in the Bulletin of the American Meteorological Society, researchers proposed an extraordinary measure to protect 25 million people, and important economic regions of 15 Northern European countries from rising seas as a result of climate change. They suggested a mammoth Northern European Enclosure Dam (NEED), enclosing all of the North Sea.

The idea involved construction of two dams of a combined length of 637 km to protect Northern Europe against “unstoppable” SLR. They also identified other regions such as the Persian Gulf, the Mediterranean Sea, the Baltic Sea, the Irish Sea, and the Red Sea that could benefit from similar mega enclosures.

A Special Report on the Ocean and Cryosphere in a Changing Climate, published last year by the IPCC, noted that “well-designed coastal protection” could both “reduce expected damages” and “be cost efficient for urban and densely populated… areas”.

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