I wasn't kidding about Alaska, btw. The worst-case projections that have alarming sea level rises also predict that much of Alaska, a truly vast area that is currently almost entirely unused, will be suitable for arable farming within the next century or so.
Regarding AI: I'm not so sure that computers, or at least Alpha, really is that dumb. The scary thing about Alpha isn't just that it's brilliant at several things - it's that the same algorithm has learnt to be brilliant at several things, and the thrust of the research is to make it brilliant at more things. Alpha has gone from being the best in the world at Go to being the best in the world at all known-information non-probabilistic games. Next up is Starcraft II, apparently - within a few years, Alpha will probably be the best in the world at all non-probabilistic concealed-information games. Then it's hard to imagine it won't rapidly become the best in the world at most of the probabilistic games as well. And all this may look like a bit of fun, except that Google aren't interested in Starcraft in its own right; they're interested in things like financial speculation, which is itself a well-defined game that Alpha will presumably come to dominate within, say, 10 or (best-case) 20 years (probably much less - every step so far as been quicker than anyone expected).
Where AI will find it harder is dealing with individual humans, whose behaviour is so suboptimal and idiosyncratic that it's much harder to predict (whereas games like chess you can mostly adopt the assumption that your opponant is at least trying to win and has some idea of how to do that). But, combined with massive surveillance data, this doesn't seem an unsolvable problem either.
Of course, AI can't do very much unless people let it. Which is why the scariest AIs are the things that governments are giving power to. The US, for instance, already uses an AI to draw up its kill lists, which humans then rubber-stamp.
But the river tripped on her by and by, lapping
as though her heart was brook: Why, why, why! Weh, O weh
I'se so silly to be flowing but I no canna stay!