One of the loopiest objections I ever heard to the idea of global warming was, as you might expect, advanced by Rush Limbaugh, who insisted that even if global warming was taking place and even if the Arctic icecaps were melting, it wouldn't be any big deal and it certainly wouldn't result in a rise of sea level, since your glass of ice water doesn't overflow as the ice cubes melt, does it?
This, of course, ignored the fact that the Antarctic ice sheets are on land (as are many of the ice sheets above the Arctic circle) and would thus create lots of runoff if they melted, which would in turn pose a problem with sea levels.
But there's another problem with global warming: as all that Arctic ice melts, the release of that much freshwater into the Northern Atlantic changes the salinity of the water there -- which, in turn, wreaks havoc with the prevailing sea currents. Like, say, the Gulf Stream, which is what keeps Northern Europe's temperatures from paralleling Eastern Canada's (which is at the same latitudes).
Cue, however, the right-wingers who will point to the snow falling in Montana or some such place as clear refutation that any warming is taking place at all.
(link via TNH)