The final bill was softened a bit, but another factor helped shift policymaking in the same direction: The election of Pat McCrory as governor in 2012 meant that the Republican Party, which already dominated the legislature, now had total control of the state government, including the coastal resources commission, which was soon reshaped to be more friendly to business.

Before the Republicans gained the upper hand, North Carolina was “a leader in really thoughtful coastal management,” said Geoffrey R. Gisler, a lawyer with the Southern Environmental Law Center.

But the commission’s 2010 report about sea level threw a scare into real estate developers, as well as some coastal residents, who worried that the state would respond with new policies that would crimp their profits or their way of life.

“A lot of folks who have interests in developing areas that are currently vulnerable, and would become more vulnerable with sea level rise, objected to the public finding out that there was this projected significant sea-level rise,” Mr. Gisler said. “And so the legislature decided to prohibit looking that far out.”

Mr. Gisler said that while its direct effects were limited, the 2012 law went hand in hand with a broader weakening in the state of environmental regulations that developers had opposed.

Under the new governor, the revamped coastal commission produced a report in 2015 that looked forward 30 years — a “shorter, more credible time period,” according to its chairman, Frank Gorham — and foresaw only six to eight inches of sea-level rise. “Everyone looked at the 2100 time period, and the people that hated it dismissed it completely, and we just lost credibility,” he said of the earlier report.

Robert S. Young, a coastal geology professor at Western Carolina University who had worked on the original report, responded in a newspaper column that “local officials may breathe easier having to look only 30 years down the road, but six to eight inches of sea-level rise are no reason to celebrate.”