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This week's Jersey floods are a taste of what's to come

Every year or two, the Jersey Shore tends to get flooding as severe as this week.

But by midcentury, the Shore should expect floods this bad every month, on average, according to projections summarized in a new U.S. government report.

The reason is rising sea levels, caused by a combination of sinking land and human-induced warmer temperatures, said the report from the National Oceanic and Atmospheric Administration.

Before he was elected, President Trump expressed skepticism that humans play much of a role in climate change. Since the election, he has said there is "some connectivity" between the two.

Climate scientists are in near-unanimous agreement that the connection is rock-solid. They say humans are the prime drivers in the cumulative 1.8-degree increase in average global temperatures since the late 19th century. The culprit is greenhouse gases, chiefly carbon dioxide released by burning gas, coal, and other fuel.

The added warmth leads to higher sea levels in two ways: the melting of ice sheets on either end of the globe, and the "thermal expansion" of water already in the ocean.

The NOAA report, coauthored by Rutgers University researcher Robert E. Kopp, summarized the most recent scientific projections on future sea levels.

If the world continues burning fossil fuels at a high rate, scientists say, it is very likely that base sea levels will rise a half-meter — more than a foot and a half — by 2100. The report describes six possible scenarios, from "low" to "extreme"; the half-meter scenario is considered "intermediate low."

But the impact will be felt far sooner than 2100, during storms and extreme high tides, Kopp and NOAA oceanographer William Sweet said in interviews.

At their peak on Monday, water levels at Atlantic City were about two-and-a-half feet above the average highest tides. In NOAA's intermediate-low scenario, floods that bad are expected on roughly a monthly basis by midcentury, Sweet said.

"This is the kind of event that could become more of the norm," Sweet said.

Even if greenhouse-gas emissions are sharply reduced, sea levels associated with the intermediate-low scenario still have about a 50 percent chance of happening by midcentury, the report's authors wrote.

But if pollution levels go unchecked, then that amount of sea-level rise is a near-certainty, according to climate projections summarized in the report.

The most dire projections call for average sea levels to increase more than 8 feet by 2100. The chance of that is estimated at well below 1 percent.

But such worst-case scenarios are important for planners to keep in mind, said Kopp, an associate professor in the Rutgers department of earth and planetary sciences.

"If that extreme scenario being correct would be catastrophic for any decision you're making, then you need to be taking that into account," Kopp said.