Not sure how seriously to take that Pentagon report... it's obviously written with a mind to increasing Pentagon funding. Hopefully it will embarrass them a bit and get attention for the environment, but I wouldn't expect war to cover the globe in 10 years...
Yeah, I think the worst-case scenario is not very likely. The part that really bothered me was the reminder that climate change is the kind of problem humans are really ill-equipped to deal with (unlike Y2K, like HIV): long term, gradual, free-rider-prone, and so on.