We must remember the rule that heat and droughts and floods are caused by global warming, but any unusually cold winters in other places are just random processes. Certainly the precautionary principle plus surface ocean acidification are enough reasons to stop digging up coal. Basing all argument on specific imagined effects makes it impossible to get the sort of global consensus you need, since obviously there are winners as well as losers, at least at the level of decadal variation.

Go Tim Flannery!

P.S. It should not be necessary to say this but just in case: The surface ocean has negative acid level [is basic] and no one is suggesting that acidification means getting all the way to positive levels.