I had a couple of problems with this book.
For one, if you are writing about global warming, I think it is a bad idea to have your World freezing. It helps the skeptics, who will of course point out that this is a contradiction in itself. While it may be possible that some places get colder on a planet with average temperatures rising, why would one want to use this aspect of global warming? There are many other unfortunate consequences of the coming disaster one could use instead.
I also had some trouble following some of the subplots. That whole part about the exorcism was rather irritating and distracting.
Also, the narration got somewhat boring at times, giving a lot of scientific details that are appropriate for non-fiction, but again only distract from the plot in a novel.
What I liked was the idea of the main character going back to living like humans before civilization in some ways. That was interesting, though it doesn’t seem to have much to do with global warming.
In all, I liked the first book in the series better.