Fossilized sediment from New Jersey's salt marshes contains evidence of a migrating coast line. For some 2,000 years, up until the dawn of our modern warming era around 1900, the sea level off of what's now New Jersey was rising by about one to two millimeters a year, with the coast itself imperceptibly creeping inland. Today, the sea level is rising by three to five millimeters a year.
Perhaps that still doesn't sound like much. But this is the point of taking a very long view of history.
"The last time we saw rates as fast as this was 6,000 years ago," says Benjamin Horton, an associate professor in the Department of Earth and Environmental Science at the University of Pennsylvania.
And what was happening 6,000 years ago? Temperatures were rising then, too, although they weren't as warm as they are today.
"Because we came out of a glacial period, oceans were warming, and ice sheets were melting," Horton says. "They're exactly the same processes that we’re seeing today."
The 10 maps contained in the GIF below show the movement of sea level at 1,000-year intervals leading up today