In the prehistoric past, Greenland was green. Paul Bierman, an environmental science professor in the University of Vermont's Rubenstein School of Environment and Natural Resources, can now say with confidence that this was true about 418,000 years ago — more recently than the millions of years ago researchers had thought. Bierman calls that discovery his only "Eureka!" moment in a 40-year career. And he would never have made it without the Cold War-era researchers who spent years living and working year-round in a city buried deep inside the Greenland ice sheet. In the 1960s, when Bierman was a child, hundreds of men drilled nearly a mile through the Arctic ice and into the frozen sediment below to extract core samples for study. Decades later, Bierman and his team used those samples, and nearly $3 million in National Science Foundation grants, to prove not only that Greenland was once a verdant landscape but that the ice sheet is more vulnerable to human-induced climate change than anyone suspected. Its disappearance, which could happen again by century's end, would have dire consequences for the more than 3 billion people in the world who live along a seacoast. [content-2] Bierman, 63, offers his findings to a general audience in When the Ice Is Gone: What a Greenland Ice Core Reveals About Earth's Tumultuous History and Perilous Future. Equal parts climate science, history lesson and cautionary tale, the book tells the story of Camp Century, a subsurface U.S. military base originally conceived to deter a Soviet attack over the North Pole. But the military soon realized that even mile-thick Arctic ice is not a stable environment. The polar outpost was abandoned in 1967, and many of its precious core samples, rarer even than moon rocks, were lost — or so scientists long believed. When the Ice Is Gone recounts how those core samples were discovered decades later in a Denmark freezer and revealed to contain plant particles hundreds of thousands of years old. Using repurposed particle accelerators from the 1960s to count ultra-rare radioactive isotopes, researchers pinpointed the age of those fossils, which were too old to carbon date. A fascinating and easily accessible read, When the Ice Is Gone has attracted considered press attention since its release in August. In part, that's because the book is free of scientific jargon and a political agenda — beyond sounding the alarm about an imminent catastrophic…