PHILADELPHIA — In June, the North Carolina legislature attempted to block a group of local scientists’ findings about how climate change could impact the state via sea-level rise. The new legislation would, for a time, prohibit the state’s coastal developers from using anything but linear estimates for rates of sea-level rise, where levels would go up by around 20 centimeters over the next century. This stands in stark contrast to the accelerating models that predict a rise of a meter over the same time period, which the local scientists, and nearly all other sea-level researchers, find to be the case.    

This episode stuck close to home for the University of Pennsylvania’s Benjamin Horton. An associate professor in the School of Arts and Sciences’ Department of Earth and Environmental Science and director of Penn’s Sea Level Research Laboratory, he is an author on a landmark research paper that draws upon fossil records — largely taken from salt marshes in North Carolina — to connect historic sea levels and their accelerating rise to climate change.

Horton has also spent much of the previous year working with fellow sea-level researchers on behalf of states that are taking the exact opposite approach toward predicting the future of their coastlines.

In 2011, the California legislature, along with several state and federal agencies, asked the National Academies’ National Research Council to produce the first regional assessment of sea-level rise. Horton was selected as part of a 12-person expert panel tasked with collecting and analyzing the relevant data for outlining potential sea-level scenarios for the coastlines of California, Oregon and Washington.

The report predicts that the West Coast will see greater sea-level rise than the global average over the next century, with some parts hit harder than others. The northern part of the coast is projected to face a 60-centimeter rise, while Southern California may experience a meter increase.    

Coming to the conclusions in the NRC’s 260-page report was the product of a long, arduous process of synthesizing the many factors that play a role in sea level. Horton’s particular area of expertise was the influence that changes in land height could have.  

Beyond global climate-change-related aspects, like melting ice sheets, the panel needed to take into account localized effects specific to the West Coast. These included weather systems like El Niño, as well as terrestrial concerns, such as the widely varying geomorphology of the coast, the impact of major cities and their associated infrastructure and even the potential of major earthquakes.

“If a major earthquake happens, which is a real possibility on the West Coast, the land could subside and sea level could go up by a meter almost instantaneously,” Horton said.

Horton is familiar with this kind of localized research; he has also been working on a $1.5 million grant from the National Oceanic and Atmospheric Administration to expand his sea-level research to six sites ranging the length of the East Coast. In the span of a month, he’s travelled to Massachusetts, Florida and back to North Carolina to work with coastal managers on how best to integrate his group’s findings with property assessments and hurricane flood plans.  

“All of these things we’ve been trying do are about taking this methodology and then focusing back in on the local level,” Horton said. “What people want to know is what’s going to happen to their houses. It all comes down to the individual.”

Horton’s travels and continued work in North Carolina has brought him face-to-face with members of NC-20, a group that backed the state’s controversial climate-change bill. His recent experiences with the NRC report and with states that have taken a more proactive approach to climate change have made such encounters all the more frustrating.

“Current sea–level conditions along the West Coast are connected strongly with the effects of El Niño, where there’s no common thread with climate change, and tectonics, which is not climate-related at all. The Carolinas are far more prone to climate-related hazards, through hurricanes and sea-level rise,” Horton said. “A state that should be so worried about climate change is the one that didn’t want to do anything about it.”