10' ... or more

The collapse of large parts of the ice sheet in West Antarctica appears to have begun and is almost certainly unstoppable, with global warming accelerating the pace of the disintegration, two groups of scientists reported Monday.

The finding, which had been feared by some scientists for decades, means that a rise in global sea level of at least 10 feet may now be inevitable. The rise may continue to be relatively slow for at least the next century or so, the scientists said, but sometime after that it will probably speed up so sharply as to become a crisis.

“This is really happening,” said Thomas P. Wagner, who runs NASA’s programs on polar ice and helped oversee some of the research. “There’s nothing to stop it now. But you are still limited by the physics of how fast the ice can flow.”

The eocene awaits.