New York Times: Thirty-five years ago, a scientist named John H. Mercer issued a warning. By then it was already becoming clear that human emissions would warm the earth, and Dr. Mercer had begun thinking deeply about the consequences. His paper, in the journal Nature, was titled West Antarctic Ice Sheet and CO2 Greenhouse Effect: A Threat of Disaster. In it, Dr. Mercer pointed out the unusual topography of the ice sheet sitting over the western part of Antarctica. Much of it is below sea level, in a sort of...