Global sea levels rose more than expected in 2024, according to a recent scientific review conducted by researchers from the California Institute of Technology, University of Hawaii at Manoa, and the Spain and International Space Science Institute.
The researchers found that seas rose 0.16 cm more than expected last year, and while this amount may seem insignificant, the data send a clear signal about the rate of climate change. Sea-level rise has already been accelerating steadily since about 1970, and scientists have determined that human-induced warming is responsible for over 70 percent of the rise in global average sea level. This study only reinforces that message.
Notably, this rise in the global average is not necessarily what is experienced at any given location. Rather, local sea-level change, which can exceed the global mean due to location-specific factors like land subsidence, dictates how sea-level rise is felt along coastlines.
What is felt are the impacts to residents, critical infrastructure, property, and ecosystems, all of which have resulted in a wave of legal challenges. Now, with sea levels rising even quicker than anticipated, this wave is likely to grow and may arrive in courtrooms sooner—meaning judges across the United States can expect to encounter a surge in cases related to sea-level rise in the coming years.
To help judges prepare for these cases, the Climate Judiciary Project recently added a new module to its Climate Science and Law for Judges curriculum about the scientific and legal dimensions of sea-level rise, co-authored by leading experts Dr. Anna Ruth Halberstadt, Assistant Professor of Geosciences at the University of Texas-Austin, and Mark Nevitt, Associate Professor at Emory Law.
Dr. Halberstadt surveys the science of sea-level rise, explaining that a warming climate affects sea-level rise in two ways: through addition of water to the oceans, such as melting from ice sheets; as well as through expansion of ocean water by warming. Scientists can project future sea-level rise using models informed by greenhouse gas emissions data, ocean circulation patterns, ice-sheet dynamics, and other factors. These projections play a critical role in helping coastal communities prepare for future impacts, such as more damaging coastal storms.
Coastal impacts come at a steep price, and the Congressional Budget Office estimates that the costs associated with hurricanes alone will grow more rapidly than the economy as sea-level rise accelerates. In response, governments and private citizens are putting into place adaptation measures aimed at building resilience in coastal areas. From coastal armoring measures (such as constructing seawalls) to funding relocation programs, these actions are often informed by complex scientific assessments of sea-level rise.
Both the impacts of and policy responses to sea-level rise present a host of legal questions. How does the law react when property boundaries shift? When does a regulation governing activity in the coastal zone constitute a taking? What risks require disclosure? Who even has standing to bring a lawsuit challenging these policies?
Nevitt sets out to answer these questions and more, focusing on the way that the science related to sea-level rise is surfacing in the courts. For example, in Severance v. Patterson, a beachfront property owner challenged Texas’ rolling easement system—which allowed easements to adapt alongside gradual changes in property lines—after a hurricane caused public easements to suddenly move onto private property. The Texas Supreme Court determined that this sudden shift did not affect property lines, but that the state could establish new public easements to cope with future events—events which could be made more impactful by sea-level rise.
Policies designed to adapt to some of the hazards associated with sea-level rise have also resulted in litigation. The California Coastal Commission, for example, has faced several challenges to setback requirements for construction based on sea-level rise projections. In each case, the Commission presented scientific evidence that informed these requirements, including the historic and projected impacts of sea-level rise as determined by the Federal Emergency Management Agency (FEMA). California state courts upheld the Commission’s setback lines following multiple challenges.
In addition, the science of sea-level rise has been used to establish an injury for purposes of standing, such as in the landmark case, Massachusetts v. EPA. There, the U.S. Supreme Court concluded that Massachusetts had suffered an injury from sea-level rise swallowing its coast, relying on the linkage between human greenhouse gas emissions, climate change, sea-level rise, and impacts to the Massachusetts coastline.
Regardless of the particular lawsuit, an understanding of the science behind sea-level rise is essential for judges to navigate these claims and understand the context from which they emerge.
To read the Sea Level Rise module and explore the rest of the Climate Science and Law for Judges curriculum, see the Climate Judiciary Project website. And for more on sea-level rise, listen to a recent episode of the People Places Planet podcast featuring ELI Visiting Scholar Jeffrey Peterson.
