As the planet warms, winter is shrinking. In the last fifty years, the Northern Hemisphere lost a million square miles of spring snowpack and in the US alone, snow cover has been reduced by 15-30%. On average, winter has shrunk by a month in most northern latitudes. In this deeply researched, beautifully written, and adventure-filled book, journalist Porter Fox travels along the edge of the Northern Hemisphere's snow line to track the scope of this drastic change, and how it will literally change everything--from rapid sea level rise, to fresh water scarcity for two billion people, to massive greenhouse gas emissions from thawing permafrost, and a half dozen climate tipping points that could very well spell the end of our world. This original research is animated by four harrowing and illuminating journeys--each grounded by interviews with idiosyncratic, charismatic experts in their respective fields and Fox's own narrative of growing up on a remote island in Northern Maine.