Chennai, Kolkata are at particular risk due to sea level rise

Climate change has numerous consequences on the daily lives of many people, but few are as palpable as rising sea levels.

Risk due to sea level rise

Many coastal communities around the world already live with the permanent threat of floods, which, driven by the melting of glaciers and polar ice caps, drown entire neighbourhoods, putting people's lives at risk and causing economic havoc.

And what is worse, if the world does not meet the objectives of the Paris Agreement and limits the increase in the global average temperature to 1.5 °C by 2050, many of the cities of the planet will see this extraordinary threat multiplied.

Sea level rise this century may disproportionately affect certain Asian megacities, including Chennai and Kolkata, as well as islands in the western tropical Pacific and western Indian Ocean, according to new research.

Chennai, Kolkata in the list

The study, led by scientists from the French National Center for Scientific Research (CNRS) and the University of La Rochelle in France and co-authored by a scientist from the National Center for Atmospheric Research (NCAR), looked at the effects of natural sea level fluctuations in the projected increase due to climate change.

The team identified several Asian megacities that may face especially significant risks by 2100 if society emits high levels of greenhouse gases: Chennai, Kolkata, Yangon, Bangkok, Ho Chi Minh City and Manila.

The study, published in the journal Nature Climate Change, showed that internal climate variability could increase sea level rise in some places by 20 to 30 percent more than would result from climate change alone, exponentially increasing flooding.

Increase sea level rise

The study showed that internal climate variability could increase sea level rise in some places by 20 to 30 percent more than would result from climate change alone, exponentially increasing extreme flooding, he said.

For example, in Manila, coastal flooding is likely to occur 18 times more by 2100 than in 2006, based on climate change alone, according to the study. But, in the worst case, they could occur 96 times more often based on a combination of climate change and internal climate variability.

Internal climate variability will also increase sea level rise along the western coasts of the United States and Australia, it added.

In just three decades, more than 570 coastal cities will face a projected rise in sea level of at least 0.5 meters, putting more than 800 million people at risk, according to data collected by the C40, which brings together a network of cities in the world committed to ecological transition.

"Internal climate variability can greatly enhance or suppress sea level rise caused by climate change," said NCAR scientist Aixue Hu, a co-author on the paper.

In the worst case, the combined effect of climate change and internal climate variability could result in local sea level rise by more than 50 percent of that due to climate change alone, "thus presenting significant risks of more severe flooding in coastal areas megacities and threatening millions of people," Hu added.

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