http://www.nytimes.com/2014/05/20/science/the-melting-isnt-glacial.html By Kenneth Chang, The New York Times. Excerpt: 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. ...A full melt would cause sea level to rise 215 feet. During recent ice ages, glaciers expanded from the poles and covered nearly a third of the continents. And in the distant past there were episodes known as Snowball Earth, when the entire planet froze over. At the other extreme, a warm p