Roughly $8.1 billion of the total $62.7 billion in losses suffered in New Jersey, New York, and Connecticut from Hurricane Sandy in 2012 can be attributed to sea-level rise caused by carbon dioxide emissions, according to a study published Tuesday by a team of researchers in Nature Communications.

The researchers, using computer modeling and reconstructions, found that warming caused by human activity raised sea levels about 4 inches in the New York area in the century preceding the storm. That was enough, they said, to force coastal flooding farther inland and deepen floodwaters.

Those heightened levels allowed the storm surge created by Hurricane Sandy in October 2012 to reach 36,000 more homes and affect 71,000 more people than if the rise had not occurred, the researchers found.

The authors, including researchers from Rutgers, Stevens Institute of Technology, and Climate Central, all in New Jersey, said the $8.1 billion estimate represented 13% of all losses. That number is the midpoint in a calculated range of losses attributable to climate change. They concluded that no less than $4.7 billion and as much as $14 billion in damage was caused by sea-level rise.

“This study is the first to isolate the sea level rise effects attributable to human activities and put a dollar sign to the additional coastal flooding damage they cause,” said Philip Orton, an associate professor of ocean engineering at Stevens who helped oversee the analysis. Orton said the research should make clear the need for urgency to act on climate change.

The authors said that the average global sea level rose about 18 centimeters (7 inches) from 1900 to 2012 and that the rise is continuing to accelerate.

Sea levels don’t rise uniformly as if in a bathtub, but are influenced regionally by both local and global factors. In New Jersey, for example, land near the coast is also sinking naturally for geological reasons. So the impact of sea rise is compounded along the state’s coast.

A separate, recent Rutgers-led study found several South Jersey areas were among the most impacted along the East Coast, with the pace of sea rise accelerating in the 20th century to about 3.6 millimeters per year. Tide gauge data in Cape May show that from 1965 to 2020 the rate of sea-level rise was about 4.8 millimeters a year, or about 1.9 inches per decade.

“Accordingly, all recent coastal floods start from a higher baseline water elevation than they otherwise would have,” the authors of the study in Nature Communications wrote.

The peer-reviewed study notes that Sandy was a powerful hybrid cyclone that caused the highest water levels in at least 300 years in the New York City metropolitan area. Plus, the researchers point out, it struck at the worst possible time because it coincided with the evening high tide and a “near worst-case storm track.”

To conduct their study, the researchers used two approaches to estimate the impact of climate change, and they produced similar findings. The researchers then modeled a range of flood-damage estimates to see how much more Sandy-related damage resulted from sea-level rise. The researchers said they could state with confidence that “human-caused sea level rise in the New York area over the past 100 years amounts to roughly four inches, or about 55% of all sea level rise observed in the area since 1900.”

“Just a hands width of sea level rise from climate change caused more than 10% of the damage from Sandy’s towering floodwaters,” said Benjamin Strauss, chief scientist at Climate Central, a Princeton-based nonprofit composed of scientists and science journalists. “The implications are enormous.”

Strauss, who conceived the study, said that sea-level rise caused by humans is already “making every coastal flood more destructive and costly. ... The costs of climate change are likely much greater than we appreciate today.”

Daniel Gilford, a Rutgers climate scientist who helped perform the analysis, said the “human impact of climate change is clear and costly.”

He said greenhouse gas emissions have warmed the atmosphere and oceans.

“As the effects of climate change grow more frequent and more severe,” he said, “documenting human impact ... is critical to understanding and reducing our adverse contributions to the climate system.”