ScienceDaily: For decades, scientists have used ancient shorelines to predict the stability of today's largest ice sheets in Greenland and Antarctica. Markings of a high shoreline from three million years ago, for example -- when Earth was going through a warm period -- were thought to be evidence of a high sea level due to ice sheet collapse at that time. This assumption has led many scientists to think that if the world's largest ice sheets collapsed in the past, then they may do just the same in our modern,...