I am looking for the title and author of a novel about a post apocalyptic Earth after a drastic climate change. The plot is similar to the movie The Day after Tomorrow, but, instead of a happy ending, the geologist ends up in a small group led by a woman (his partner) wandering around USA. There is extreme cold, food is scarce.
I think that instead of a geologist, it may be a historian. (Or the woman is). Also, it has something of survivalist focus, with intents from the male protagonist to contact (unsuccessfully) other survivors. Dogs become feral and attack human.
In the end, the woman becomes the leader of the band of the survivors and, in the end, she leaves the male main character to die because he is unable to cope with the "new world" and refuses to acknowledge that the world has changed forever.