I read Matthew Glass's Ultimatum this weekend. Only so-so. What's weak about it, as a scenario exercise, is that Glass creates his imaginary future by running forward a rather extreme set of climate numbers, and the most optimistic numbers about Chinese growth, but otherwise holding everything entirely static. Thus, despite the fact that vast evacuations of costal areas are now necessary (something he portrays only from the Olympian heights of the White House war room) and the Chinese economy is now twice the size of the U.S.'s, political alignments both domestically and globally are unaltered. How realistic is that?
What makes it so hard to prognosticate a couple of decades out, on virtually any subject, is that there are so many moving variables that one has to consider. Things Glass doesn't bother to consider, for example, is how radical genetic engineering may fundamentally change conceptions of practices of life; how major shifts in geopolitical alignments can take place very quickly (France-German, 1945-1951; U.S.-China in 1971; U.S.-Iran in 1979; U.S.-Russia in 1989, etc.); how aging populations may fundamentally change immigration politics; how coming egenry shortages are going to fundamentally shift adaptation options; and so on.
The result is that the book reads like a Bolshie Brit's fantasy about what it would be like if a belligerent version of Obama had been elected President in 2033, and then appointed Bill Kristol as his Secretary of State.
However, within that structurally weak frame, the novel is quite illuminating about how lefty Brits view American and Chinese politics today, and why ever getting an emissions deal done will be impossibly difficult.
Finally, Glass never considers that as the catastrophe happens, it may not even really be perceived as a catastrophe at all. That's the key insight of J.G. Ballard in The Drowned World.