Roughly 1 in every 20 people worldwide lives within 21 feet vertically of the sea, exposing them to an increasing risk of flooding as climate change causes rising sea levels. On September 30th, the Energy Policy Institute at the University of Chicago (EPIC) hosted the first in a two-part series on this vital topic with Bob Kopp, the associate director of the Rutgers Energy Institute at Rutgers University–New Brunswick.
Geological records show that global average sea level rise during the 20th century was faster than any of the previous 26 centuries, and modern observations reveal that global sea level has risen since 1993 at about 2.5 times the rate earlier in the 20th century. Kopp discussed the many factors contributing to these changes, the largest of which – melting land ice and thermal expansion – are associated with climate change.
We can expect this rapid rate of sea level rise to continue to increase, Kopp said, though efforts to reduce emissions would limit the rate of change. But even the most aggressive mitigation efforts would not, in the long run, entirely prevent vast flooding impacts. The last time global mean temperatures were about 1°C (1.8°F) warmer than today, about 125 thousand years ago, sea level was more than 21 feet higher. While it’ll probably take centuries or millennia to realize such a change, limiting future global warming to just 1°C (1.8°F) goes far beyond the goals of all but the most ambitious climate change mitigation policies.
What will these rising seas cost society?
To give an illustration, Superstorm Sandy cost about $18 billion in damages to New York City alone. Three feet of sea-level rise would make such damaging storms about twice as likely as at present, and 7 feet of sea-level rise would make them about 11 times more likely. Looking forward, Kopp drew upon a range of different sources of information to project a likely sea-level rise at New York City of 2 to 4 feet over the 21st century, with a 1-in-200 chance ‘fat tail’ of 7 feet.
Figuring out how to manage uncertain future sea-level rise depends both on a decision maker’s risk tolerance and the decision timeframe. And, Kopp cautioned, the consequences of our decisions often last much longer than we might think.
As an example, Kopp described the Marion Power Station in Jersey City, New Jersey. The power station was built in 1905 by Thomas Alva Edison’s power company, and the regional electric grid developed around it. Although Marion and its contemporary power plants were shuttered decades ago, the structure of the grid remains – and more than half the switching stations that were flooded and shut down by Superstorm Sandy, depriving much of New Jersey of electricity for a week or more, were at locations sited during Marion’s era, more than a century before.
Knowing that rising seas will be a major challenge moving forward, and that it will cost coastal communities billions of dollars, how do we move forward? Do we rebuild unchanged after each flood event, with coastal regions continuing to depend upon subsidies from interior parts of the country? Do we harden defenses by building stronger levy systems to fend away the rising seas, like those that have been built in the Netherlands and elsewhere? Do we raise structures and strive to make communities more resilient to periodic flooding? Or do we simply retreat back from the coast, and rely upon salt marshes and other ‘green infrastructure’ as buffers?
How we decide depends on how we think about the problem. Kopp says that we could think of it technocratically, using land-use policy informed by benefit-cost analysis. We could also think of it economically, using market tools such as accurately-priced, long-term flood insurance. Lastly, we could think of it democratically, through deliberative community processes.
“We should do all three,” Kopp says. “The one thing we can’t do is wish, or legislate, sea-level rise away.”