Centuries from now, a large swath of the West Antarctic ice sheet is likely to be gone, its hundreds of trillions of tons of ice melted, causing a four-foot rise in already swollen seas.

Scientists reported last week that the scenario may be inevitable, with new research concluding that some giant glaciers had passed the point of no return, possibly setting off a chain reaction that could doom the rest of the ice sheet.

For many, the research signaled that changes in the earth’s climate have already reached a tipping point, even if global warming halted immediately.

“We as people see it as closing doors and limiting our future choices,” said Richard Alley, a professor of geosciences at Pennsylvania State University. “Most of us personally like to keep those choices open.”

But these glaciers are just the latest signs that the thawing of earth’s icy regions is accelerating. While some glaciers are holding steady or even growing slightly, most are shrinking, and scientists believe they will continue to melt until greenhouse gas emissions are reined in.

“It’s possibly the best evidence of real global impact of warming,” said Theodore A. Scambos, lead scientist at the National Snow and Ice Data Center.

More at: http://www.nytimes.com/2014/05/20/science/the-melting-isnt-glacial.html?hpw&rref=science&_r=0