The costs associated with sea-level rise projected for 1.5C and 2C of warming are substantial, according to new research. But megacities are likely in less danger than rural coastal communities due to the economics of the problem.
If the worst projections for rising sea levels come to pass, the global economy could take a hit of as much as US$27 trillion a year in flood damage and adaptation costs, according to new research.
In a paper out this week in Environmental Research Letters, researchers with the UK’s National Oceanography Centre project assessed the likely costs from sea-level rise associated with the two Paris Agreement targets, and the costs from what may happen if the international community misses them.
Canada’s national agreement on climate change, the Pan-Canadian Framework, recognizes the country has one of the longest coastlines in the world, with the greatest risk from sea-level rise faced by the Atlantic provinces, the Gulf of St. Lawrence, the Beaufort Sea, Haida Gwaii, parts of Vancouver Island and other parts of the BC coast.
The researchers estimate that 2C of warming, producing an average global sea-level rise of up to 63 centimetres by the end of the century, would cost the global economy $1.4 trillion a year more than the costs associated with 1.5C of warming, with an average global sea-level rise of up to 52 centimetres.
If the international community blows through the Paris Agreement’s 2C target, and follows a high-emissions scenario—whose trajectory emissions growth currently matches—sea levels will rise 86 centimetres, say the researchers, with a worst-case scenario of 180 centimetres. These scenarios would see costs climb up to $14 trillion and $27 trillion a year, respectively, or 2.8 per cent of global GDP in 2100.
Upper middle-income countries such as China would be worst hit with flood costs, soaring to eight per cent of GDP. But high-income countries like Canada and Germany would have lower projected costs due to their already high levels of flood protection standards.
However, the researchers report that with robust adaptation measures, costs could be reduced by a factor of 10.
Separately, another paper also out this week in Nature Climate Change, explored sea-level rise impacts and adaptation across six emblematic regions: Bangladesh, New York City, the Netherlands, the Maldives, Catalonia and Ho Chi Minh City.
The group of coastal engineers, economists and social scientists behind this study wanted to find out to what extent these locations are able to adapt, given that they are already confronting sea-level rise challenges and in some cases social conflicts resulting from these difficulties. At the same time, they wanted to leap over negative narratives of sinking islands and submerged megacities, and produce a comparative analysis that might be able to tease out lessons that apply across all such places, and thus potentially other locations.
Across all cases, the researchers concluded that economic barriers, in particular finance and social conflict related to economics, are reached long before any technological limits to coastal adaptation appear. By this they mean that coastal adaptation tech is quite mature, and in principle, they say, there is no technical obstacle to engineering coastal protections to very high standards. The problem is whether societies are able to access sufficient finance to pay for this, and even when they can afford such endeavours, whether all groups in society are willing to accept the spending of large amounts of public money for these purposes rather than other policy areas.
The researchers add that in low-lying areas with high population densities and substantial assets, it makes economic sense to protect even against worst-case extreme sea-level rise, regardless of the cost of such infrastructure. It is “very unlikely,” they say, therefore that there will be any megacities submerged by sea-level rise this century.
However, protecting rural coastal areas and agricultural land have much lower cost-benefit ratios, and so in such cases, these may be assessed as lower priority and distributional conflicts may arise as to whether such locations should be equally well protected as cities.
The researchers deliberately included the adaptation measure of retreat from coastal areas as it is in principle always possible and not technologically limited, but noted that it is likely rural and poorer areas will struggle to maintain safe human settlements and so will likely eventually retreat. It is probable that in such circumstances, this will involve “massive social conflict”, not least with respect to compensation.
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