Ash Adams for The New York Times
ANCHORAGE — A few miles and a few days from this weekend’s start of the Iditarod sled dog race, a glaciologist named Shad O’Neel stood in his sun-drenched office at the United States Geological Survey, talking about climate change.
The walls displayed striking before-and-after photographs of the Columbia Glacier and others in Alaska. Even a nonscientist could see that they were shrinking, sometimes radically so in a decade or less.
O’Neel pulled out a color-coded map of mountain ranges in the southern part of the state, including the Alaska Range, through which 52 sled dog teams race north along the Iditarod trail on their 1,000-mile trek to Nome.