Sea Level Rise: Not just for the Maldives (it’s Miami and Mobile and Myrtle Beach, too!)

  • Published on August 23rd, 2018

When we think of sea-level rise due to global warming, we tend to think of beaches eroding or perhaps tiny Pacific nations such as the Maldives slowly disappearing. The reality, however, is that it won’t be countries or country sides bearing the economic brunt of sea-level rise, but cities.

Daily tidal flooding in South Beach, Miami
Daily tidal flooding in South Beach, Miami


Here are some important snippets of a 2011 economic projection report by McKinsey, Urban world: Mapping the economic power of cities:

Today only 600 urban centers generate about 60 percent of global GDP. […] By 2025, 136 new cities are expected to enter the top 600, all of them from the developing world and overwhelmingly—100 new cities—from China. […] Today’s 23 megacities—with populations of 10 million or more—will contribute about 10 percent of global growth to 2025, below their 14 percent share of global GDP.

The first and most obvious thing about the above points is that cities are by far the richest and most valuable real estate in the world and by definition tiny compared to countries. That means that point adaptation by the richest cities is much more viable than for most of the rest of the countries they are in.

The second obvious thing is that while many of the richest cities today are at sea level, not all are. And the geography of those cities varies substantially. Here are the top 10 of the 25 from the McKinsey report and their shifting status by different metrics.

Only six of the current ten highest GDP cities are actually exposed to sea level rise concerns. The current projected average sea level rise by 2100 is a meter. IPCC 5 had it pegged at a median of 60 centimeters or 2 feet, but rejected some papers which saw greater rise due to a lack of explanatory mechanisms. The research has firmed up since then.

The next important point is that sea level rise varies substantially. It’s greater at the equator than at the poles due to centripetal force and thermal expansion. Tokyo is projected to receive 45% greater sea level rise than average, as a key example. It will see closer to 1.5 meters or 5 feet, in other words.

And, of course, average sea level rise is only one problem. Most seaside cities are now exposed to more severe risks from cyclones, with Asian typhoons hitting land having increased in both severity and frequency over the past 40 years. From Hurricane Sandy hitting New York to Harvey over Houston, greater damage is occurring in large part due to greater intensity, size and moisture content of major storms. With storms come storm surges that are meters higher and rains which cause inland flooding which meet the storm surges, leaving neither anywhere to go but up.

But what about the major cities identified as the fastest growing by 2025 per McKinsey?

Several cities have fallen off the top ten list, but there are still 6 cities threatened by sea level rise. While the average elevation of the cities has increased from around 56 meters to 95 meters, the average is not a useful metric. What is interesting is that more of the growth cities are inland, not at sea level.

The cities which have been added have strengths and weaknesses on this front. A strength is that they are Chinese cities in a command-and-control economy that understands the impacts of sea level rise and is taking it seriously. Their development and which cities are in special economic zones will take this into effect, so they likely will be more resilient. A key downside is that the legacy Asian cities are much less resilient than New York and Tokyo due to lower investments in resilience for the past few decades.

Will sea level rise impact economic growth? Absolutely and negatively. Very expensive infrastructure will be abandoned or require massive and expensive protection. That money, while it is still an economic driver, could be better invested elsewhere for better economic outcomes.

Will all seaside cities be impacted equally? No, Miami, which doesn’t even make the top 25 cities, will suffer much more than most cities due to a confluence of issues: sea level rise, coastal subsidence and porous limestone. Dhaka, which does show up on the list as a top performing megacity, could easily see 27 million people impacted severely by sea level rise by 2050. It was already impacted by the 2017 massive monsoon flooding, although the worst impacts were north of the city.

Will the economy of the earth survive? Of course. Will we see reduced economic growth? Also of course.

One projection has a price tag of $14 trillion USD by 2100. Another has a trillion USD of property value loss in the United States alone. These are big numbers. The global GDP is only 78 trillion USD.

This is why governments which are actually serious about the economy and their citizens are united globally in an effort to slow global warming. And this is a significant reason why the United States current regression is deeply unfortunate, not only for the USA and its citizens, but also for the world.


(Originally appeared at our sister-site, Cleantechnica. Photo CC by MiamiBrickell on Flickr)

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