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04-06-2023

Asian megacities at highest risk from sea level rise

A recent study published in Nature Climate Change has identified the areas most at risk from sea level rise caused by natural ocean fluctuations and climate change. 

The research, which was supported by the US National Science Foundation and co-authored by a scientist at the National Center for Atmospheric Research (NCAR), mapped sea-level hotspots across the globe.

The study revealed that certain Asian megacities are particularly vulnerable, including Chennai, Kolkata, Yangon, Bangkok, Ho Chi Minh City, and Manila. The authors warn that these cities may face significant risks by 2100 if society continues to emit high levels of greenhouse gases.

“Internal climate variability can greatly reinforce or suppress the sea-level rise caused by climate change,” explained NCAR scientist Aixue Hu, who co-authored the paper. “In a worst-case scenario, the combined effect of climate change and internal climate variability could result in local sea levels rising by more than 50% of what is due to climate change alone, thus posing significant risks of more severe flooding to coastal megacities and threatening millions of people.”

The study used a computer model of global climate and a specialized statistical model to determine the extent to which natural fluctuations can amplify or reduce the impact of climate change on sea-level rise in certain regions. 

The researchers found that internal climate variability could increase sea-level rise in some locations by 20%-30% more than what would result from climate change alone, exponentially increasing extreme flooding events.

For example, the study predicts that coastal flooding events in Manila will occur 18 times more often by 2100 than in 2006 based solely on climate change. In a worst-case scenario, 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 west coasts of the US and Australia.

While the study acknowledges the uncertainties associated with predicting sea-level rise due to the complex and unpredictable interactions in the Earth’s climate system, the authors stress the importance of developing effective adaptation strategies.

“The paper emphasizes that the estimates of sea-level rise come with considerable uncertainties because of the complex and unpredictable interactions in Earth’s climate system,” the researchers wrote. “But the authors said it’s critical for society to be aware of the potential of extreme sea-level rise to develop effective adaptation strategies.”

The current predictions for sea-level rise worldwide vary depending on the rate of greenhouse gas emissions and the resulting climate change. According to the Intergovernmental Panel on Climate Change (IPCC), global sea levels have already risen by about 15 cm since the start of the 20th century.

The IPCC’s fifth assessment report, published in 2014, projected a global sea-level rise of between 26 and 82 cm by 2100, depending on the rate of greenhouse gas emissions. However, more recent research suggests that the upper end of this range may be an underestimate, and that sea-level rise of over one meter by 2100 is possible if emissions continue to rise at their current rate.

It’s worth noting that sea-level rise is not uniform around the world, and some regions are more vulnerable than others. The study discussed in this article, for example, identified certain Asian megacities, western tropical Pacific islands, and the western Indian Ocean as particularly at risk from sea-level rise. Other vulnerable regions include low-lying coastal areas, such as the Netherlands, Bangladesh, and small island states in the Pacific and Indian Oceans.

It’s also important to note that sea-level rise is a slow process and may not be immediately noticeable in many places. However, it can have significant impacts on coastal communities, ecosystems, and infrastructure over time, particularly when combined with extreme weather events such as storms and hurricanes. Developing effective adaptation strategies will be critical for minimizing the impacts of sea-level rise in the coming years.

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