New Study Triples Global Estimates Of Population Threatened By Sea Level Rise

By Teodor Teofilov

Hundreds of millions of people across the globe will be at risk of losing their homes as whole cities sink under the rising sea levels over the next three decades, according to a Climate Central study published in the journal Nature Communications on October 29. Climate Central is a non-profit science and news organization providing information to help the public and policymakers make sound decisions about climate and energy.

The findings show that nearly three times as many people living in coastal areas are at risk from flooding than previously thought. Global sea levels are expected to rise between 0.6 meters to 2.1 meters (two to seven feet) and more over the course of the 21st century.

Land that is currently home to 300 million people will flood at least once a year by 2050 because it will fall below the elevation of the average annual coastal flood, even if reductions in carbon emissions are roughly in line with 2015 Paris Agreement targets, which worldwide efforts to date are not on track to achieve. By 2100, land home to 200 million people could be permanently below the high tide line, making those coastal areas unlivable. This is far more than the previous estimate of 80 million.

This upward increase is based on a more sophisticated assessment of the topography of coastlines across the globe. Previous models used satellite date that overestimates the altitude of land because of tall buildings and trees. The Climate Central study used artificial intelligence to compensate for such errors.

“These assessments show the potential of climate change to reshape cities, economies, coastlines, and entire global regions within our lifetimes,” said Scott Kulp, a senior scientist at Climate Central and lead author of the study in a press release. “As the tideline rises higher than the ground people call home, nations will increasingly confront questions about whether, how much, and how long coastal defenses can protect them.”

The researchers said that the magnitude of difference from the previous Nasa study came as a shock.

“It turns out that for most of the global coast, we somehow didn’t know the height of the ground beneath our feet,” said Benjamin Strauss, chief scientist and CEO of Climate Central and co-author of the study. “We were shocked to find how much more vulnerable our coasts are than researchers had previously thought. But this also means there are much greater benefits to reducing climate pollution and slowing sea level rise.”

Without enough sea defenses in place entire coastal cities could sink under the sea. According to the study, about 70 percent of the people at risk of yearly floods and permanent flooding are in eight countries in Asia — China, Bangladesh, India, Vietnam, Indonesia, Thailand, the Philippines, and Japan. The Climate Central press release highlights that China’s low-lying big cities are particularly vulnerable.

The threat is already being felt in Indonesia, where the government announced in August that it would be moving the capital city out of Jakarta, which is sinking and is vulnerable to floods. The Climate Central figures show that the number of people at risk in Indonesia is up from the previous estimate of 5 million people to 23 million.

It’s not just Asia that will feel the impact of the rising sea levels in the 21st century either. The study says that 19 other countries, such as Brazil and the UK can see their land falling permanently below the high tide line by 2100.

“If our findings stand, coastal communities worldwide must prepare themselves for much more difficult futures than may be currently anticipated,” the study warned. “Recent work has suggested that, even in the US, sea-level rise this century may induce large-scale migration away from unprotected coastlines, redistributing population density across the country and putting great pressure on inland areas.”

The study warns that the calculations are conservative and could underestimate the dangers and impact of the rising sea levels, because they are based on the standard projections of sea level rise in the Representative Concentration Pathway 2.6 (RCP2.6) scenario. This scenario assumes that emissions will be cut in line with the Paris agreement and keep the global temperature from rising above 2 degrees Celsius, which countries are currently not on course of meeting.

The researchers say that in a scenario of unchecked emissions and early-onset ice sheet instability, the sea level rise will threaten the livelihood and homes of as many as 630 million people worldwide by 2100.

A key report by the United Nations’ Intergovernmental Panel on Climate Change (IPCC), showed that the impacts of climate change are increasing and inevitable. Glaciers and ice sheets in polar and mountain regions are losing mass at an increasing rate, adding to rising sea levels.

“In recent decades the rate of sea level rise has accelerated, due to growing water inputs from ice sheets in Greenland and Antarctica, in addition to the contribution of meltwater from glaciers and the expansion of warmer sea waters,” said Valérie Masson-Delmotte, Co-Chair of IPCC Working Group I, in the press release.

The rising oceans will be disastrous for people living in coastal cities, as they will be forcibly displaced. Pacific islands could be sunk and this would create huge waves of climate refugees who won’t have anywhere to go, as they aren’t protected by international laws and countries won’t have to give them asylum legally. The rising sea levels add to global temperature increase and will affect the crops that can be grown and will have a detrimental impact on fishing. This means that millions could face food and drinking water shortages, health crises and a heavily damaged global economy.

You can check out Climate Central’s interactive threat maps at or here.

The study in the journal Nature Communications is here.

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