Helping climate science make sense.

Trillions at Stake in Sea Level Rise for 20 Global Port Cities

It’s easy enough to appreciate that sea level rise brought on by climate change poses a hazard to people and property. It’s not so easy, however, to predict exactly how many people are likely to be affected, and how much damage the rising seas are likely to do. Climate Central spent many months doing its own analysis for the U.S, for example, and found that nearly 5 million Americans will be at severely elevated risk from coastal floods by 2030 (you can calculate your own exposure with our searchable interactive Surging Seas map).

Now the Organization for Economic Cooperation and Development (OECD) has weighed in with its own assessment — what it calls an environmental working paper, which looks at the risks to major port cities around the world. The report is rather dense for ordinary readers to plow through, but Bloomberg thoughtfully summarized the findings in a slideshow titled “Top 20 Cities with Billions at Risk from Climate Change.”

Miami is the city with the most to lose from rising seas in the entire world, says new analysis. Credit: Florida Insurance Claim Lawyer Blog.

Asian cities grabbed 13 of the 20 spots (including places you’ve probably never heard of, such as Qingdao and Ningbo, in China). But the dubious honor of first place goes to Miami, with $3.51 trillion and 4.8 million people at risk by 2070. Two other American cities made the Top 10 as well: New York City and Newark, N.J., share the No. 3 spot, with a combined $2.1 trillion in likely losses, and 2.9 million people at risk by 2070. Two more – New Orleans and Virginia Beach – were also in the Top 20, at Nos. 12 and 19, respectively.

The authors of the OECD report based their calculations on the risk of a hundred- year flood — that is, a flood so large it’s likely to happen only once a century, on average. Coastal floods are generally caused by storm surges, like the one Hurricane Katrina pushed into New Orleans. With rising seas, a hundred-year flood will happen more often.

Sliced by population rather than city, and looking at today rather than the future, the report found that about 10 percent of the affected cities’ populations, or a total of about 40 million people, and $3 trillion of property, are already susceptible to these devastating, once-in-a-century floods (and of that $3 trillion, 60 percent is found in just three countries: the U.S., Japan, and the Netherlands). By 2070, says the report, the combined effects of population growth, migration to cities, and rising seas will boost those numbers to 120 million people and $35 trillion.

That being the case, the closing line of the report’s summary seems like a pretty gross understatement: “. . . the benefits of climate change policies – both global mitigation and local adaptation at the city-scale – are potentially great.”

« Climate in Context