"melting more ice into water/water vapor --> more unpredictable weather patterns --> greater frequency of strong storms"

This chain of events has NOT been shown yet (If i recall, hurricane activity is not actually higher than ~30 years ago - it just seems that way b/c we have far greater access to news and greater development in hurricane areas) -- of course it is plausible that during a "fast" (.1 deg/decade) global temperature change weather patterns would become very disturbed.

Also, more water vapor tends to mean more clouds (more storms? -- possibly) and clouds tend to reduce the total heat transfer to the earth... of course whether or not the cloud effect is less than the effect of extra water vapor is also unknown because of the difficulty in modeling cloud formation.

"As for no-one doing anything about it, well, most of the world agreed to the Kyoto Accords"

True enough, but RATIFYING Kyoto is not the same thing as actually doing anything. In fact, if I recall, most "Kyoto nations" have not actually gotten very far in reducing their emissions - of course it is still early...

"but the US didn't, citing "loss of corporate productivity" or profits, or something."

Yes, but it also declined b/c the treaty did not include the fastest growing polluters: China and India. Also, the US believes that technological transformation is the solution (whether this can happen fast enough is a good question) and joined a Asia-Pacific partnership to this end (though critics do say this is bogus - time will tell, I suppose)