At Winter's End - Robert Silverberg - Bog

After seven hundred thousand years underground, one tribe emerges to explore the new world
The time of falling death stars ushered in the Long Winter-eons of cold that caused plants and animals to vanish from Earth and drove people to take refuge in underground cocoons. Human ingenuity had never faced a greater challenge. For seven hundred thousand years, generation after generation was born and died below the Earth's surface. But now, one small tribe is sensing change. Chieftain Koshmar is sure that the New Springtime is near, so she leads her people above ground to explore the new world that awaits. The unfamiliar Earth, still a frozen shell of its former self, will test their mettle in every way, leading the people of the tribe to the brink of their destiny-or to their doom. At Winter's End is the first book of the New Springtime series, which continues with The Queen of Springtime.