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Rising sea levels could cost the U.S. trillions

Adapted from Sweet et al. 2017 and EPA 2017; Note: “Adaptation” refers to property elevation, beach nourishment, and shoreline armoring; Chart: Harry Stevens/Axios

One of the most dire, and expensive, scenarios of climate change damage in the Fourth National Climate Assessment — the report the Trump administration released on Black Friday — is the rising sea levels that are already causing problems in coastal cities from New Orleans to Boston.

Why it matters: The report says the U.S. will have to ratchet up actions to adapt to global warming-related impacts at the same time that cuts to greenhouse gases are made. But since the climate is a complex system that's tough to turn around on a dime, a certain amount of warming and sea level rise is baked into the next few decades.

“We’re gonna have to adapt no matter what."
— Michael Oppenheimer, geosciences professor at Princeton University

These charts, which were adapted from the assessment, show possible trajectories that global average sea level rise may follow. The outcome would depend on several factors, including greenhouse gas emissions from burning fossil fuels, as well as the response of the world's ice sheets and glaciers to increasing temperatures.

  • Notably, the climate assessment includes some of the latest guidance showing that parts of Antarctica are far less stable than previously thought. That's why its sea level rise projections are higher than prior reports from the U.N. Intergovernmental Panel on Climate Change (IPCC).

The backstory: The bottom part of the figure shows how sea level rise could affect the U.S. economy by damaging valuable real estate and infrastructure in coastal communities.

  • Specifically, the chart shows cumulative damages (in 2015 dollars) to coastal property in 17 multi-county coastal areas — including the Miami and New York City areas under different emissions and adaptation scenarios.

Details: According to the report, cumulative damages under the high emissions scenario could run as high as $3.6 trillion through 2100 if there are no actions taken to protect coastal infrastructure and property from rising seas. By contrast, the cost could be reduced to $820 billion under the same scenario if those measures are implemented.

Under a lower emissions scenario, the costs without adaptation would amount to $892 billion, which could be cut to $800 billion with adaptation.

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