President Trump announces that the United States will withdraw from the Paris climate agreement in the Rose Garden of the White House on June 1. (Kevin Lamarque/Reuters)

Wittingly or not, James Eskridge, mayor of a town on a small island in the Chesapeake Bay, used one of the savviest possible tools for letting President Trump know about a problem his constituents were facing: He talked about it on television.

“Donald Trump, if you see this, whatever you can do, we welcome any help you can give us,” Eskridge said. The problem Tangier Island faces is an existential one: It is shrinking by 15 feet a year, according to the Army Corps of Engineers. The reasons for that are elementary. The island is eroding, and the seas are rising.

Or, if you ask the president, just the first one.

As our Travis Andrews reported, Trump told Eskridge that “we shouldn’t worry about rising sea levels,” Eskridge said. “He said that ‘your island has been there for hundreds of years, and I believe your island will be there for hundreds more.'” Eskridge, who is “on the water daily,” said that he was inclined to agree.

The data, however, don’t. For nearly a century, the sea level has been recorded at a station at Sewells Point, Va., about 60 miles south of Tangier Island. Over that period, the mean sea level at Sewells Point has increased by two feet.

This is not specific to Sewells Point. The National Oceanic and Atmospheric Administration estimates that the sea level at Sewells Point rises by about 4.6 millimeters a year. (That’s about 0.0126 millimeters a day or about half the length of a skin cell. No wonder Eskridge doesn’t notice it.) At Ocean City, Md., the figure is about 5.6 millimeters. At the NOAA’s measuring station at the Chesapeake Bay Bridge Tunnel, it’s about 5.9 millimeters.

The biggest increases are on the Gulf Coast, near Louisiana.

Why is this happening? In part because of climate change.

As the world warms, it melts glaciers and other ice masses that then flow into the oceans, increasing the volume of water. But warming water also increases its volume, and as Earth warms, so do the oceans. (This is basic physics. Think of a thermometer: The outside temperature causes the mercury to expand within the marked tube.)

Since 1901, oceans have grown significantly warmer just about everywhere in the world.

There’s an exception near Greenland, you’ll note — which is in part a function of cold water from melting ice entering the ocean.

If we consider ocean temperatures as a function of the average temperature in the 20th century, the recent increase is clearly visible.

The question, then, isn’t whether sea levels are rising or why that’s happening. It’s why Trump so readily dismissed the idea that they were.

The answer to that is likely political. Trump avowedly rejects the science of climate change, which in part led him to withdraw from the Paris climate accord. While he has in the past acknowledged that the climate is changing and even that humans may play a role in that, his default position is that the entire effort to combat climate change and its effects is at best unnecessary.

The Army Corps of Engineers is going to build a jetty on Tangier Island that will reduce the erosion caused by currents in the bay. The Trump administration doesn’t seem poised to do much of anything about the problem of rising sea levels, though.

A website run by the NOAA shows precisely what will happen to Tangier if sea levels rise another foot: Most of it will be underwater.

At 4.6 millimeters a year — assuming that rate holds steady — that would happen in another 66 years.

Not quite the “hundreds of years” that Trump promised.