Coastal communities may have even less time to prepare for rising seas than previously thought, a new study says.
The report, released Monday by the Union of Concerned Scientists, projects that climate change-driven sea level rise could make nearly 311,000 existing residential and commercial properties in the U.S. uninhabitable by 2045. Those properties are all in the contiguous 48 states and collectively worth $136 billion. If carbon emissions and rapid ice sheet loss are not curtailed, chronic flooding will render these homes and businesses unusable by 2045, the study says.
According to this projection, buyers closing on one of those properties today would have to abandon or rebuild it before they could pay off a standard 30-year mortgage. A shrinking property tax base would deprive municipalities of revenue to provide public services, let alone upgrade infrastructure to protect against continued sea level rise. As this unfolds, it could drive climate liability suits, experts said.
“We don’t know how communities may pursue suits in court, but given the magnitude of the risk, it’s not surprising that many communities are looking for ways to pay the huge sums of money they’ll need to address those risks,” said the study’s lead author, climate scientist Kristina Dahl.
The study, “Underwater: Rising Seas, Chronic Floods, and the Implications for US Coastal Real Estate,” combined each of three possible sea level rise scenarios with 2017 databases from online real estate company Zillow. Put together, the data quantified the impact on property values and tax revenue. Researchers used high, intermediate and low sea level rise projections developed for the 2014 National Climate Assessment. The report focused on the high scenario, which assumes unabated carbon emissions and ice sheet loss that continues at a rapid pace, which would raise global sea level 6.6 feet over the 1992 level by the end of this century.
The low scenario assumes countries meet the Paris Climate Agreement’s goals for curtailing global warming, which would drastically reduce property loss of the high scenario.
The study then looked in depth at “chronic inundation,” which it defined as flooding that occurs 26 times per year. Dahl and her team used existing research and interviews with coastal property owners in cities at risk, such as Annapolis, Md., to determine when frequent flooding would cause communities to take action.
“Previous studies have looked at very long timeframes, at a moment in the future when a property is underwater at every high tide. But no property owner is going to sit and wait for that,” Dahl said. “We were looking at a threshold for when it’s no longer sustainable to stay in the property. When you look at sea level rise in that way, we see that the threat is much closer at hand than the end of the century.”
Dahl, who conducted the data analysis, said the number of properties at risk in the near future was higher than she had expected. “We’ve known for a long time that sea level rise would create these risks in the longer term, but the near-term risk has really been flying under the radar,” she said.
Most coastal real estate markets haven’t yet been harmed by sea level rise projections.
“Theoretically, a market should price in risk, but I don’t think most of us think about 100 or even 30 years from now. We heavily discount the future,” said Deborah Sivas, an environmental law professor at Stanford Law School. “The property and insurance markets have not taken seriously what scientists are telling them. You can still get a mortgage and insurance when you’re in harm’s way.”
Experts say current practices for setting insurance rates also contribute to short-term thinking by buyers. “The insurance industry already knows sea level rise is coming, but they price on a year-to-year basis, and they can’t change that themselves” without fundamental public policies changes, said Lindene Patton, a strategic advisor on risk management and former chief climate product officer for the Zurich Insurance Group.
As the pace of property damage increases during the next few decades, more communities may sue for climate change-related damages, experts said.
The study’s projections are “foreboding for a time that municipalities will have major expenses to adapt to rising sea levels,” said John Miller, a water resources engineer who studies the connection between credit ratings and climate change at the Wharton Risk Center at the University of Pennsylvania. “This plays into municipal credit, as a drop in revenues will be credit negative and could result in a downgrade, meaning that issuing debt will be more expensive and that could result in higher taxes. I think this will push local governments to look for any way to make up revenue, including going after carbon intensive industries.”
Publication of the report itself could drive more climate litigation, Sivas said. “My guess is we’ll see more suits as local governments get emboldened. If you’ve got more data coming out, it could tip some cities that otherwise would stand back,” she said.
Among the study’s other findings:
- About 175 communities nationwide can expect significant chronic flooding by 2045, threatening 10 percent or more of their housing stock.
- Of the 175 at-risk communities, nearly 40 percent have poverty levels above the national average. The combination of poverty and chronic flooding creates hotspots of heightened risk in Louisiana, North Carolina, New Jersey and Maryland.
- In the next 30 years, about 14,000 commercial properties will be at risk along U.S. coasts. Of these, “more than one-third are in Florida and New Jersey. Those same two states are home to 45 percent of the commercial properties, coastwide, that would be at risk by end of the century,” the report says.
- By the end of this century, the number of at-risk properties is projected to grow to nearly 2.5 million, collectively valued at more than $1 trillion.
- Projected property damage falls dramatically when the projection uses lower carbon emissions and slower melting of land-based ice. “If the global community adheres to the primary goal of the Paris Agreement of capping warming below 2°C (UNFCCC 2018), and with limited loss of land-based ice, the United States could avoid losing residential properties that are currently valued at $780 billion, contribute $10 billion annually in property tax revenue, and house 4.1 million people,” the report says.