My impression was that you're approaching the thermohaline inversion backward. It's not that it would plunge us into a new ice age, it's that it *might* plunge *northern Europe* into a new ice age. Warm water from the mid-atlantic flows north past the US continental shelf, turns east when it hits southward-running cold currents coming off Greenland's east coast, and then procedes to do a loop around England, Scandinavia, and the Arctic Ocean. Vacation spots in France, Italy, and Spain are at the same latitude (and therefore get the same amount of solar flux coming into their atmosphere) as snowy Vermont. London lines up with polar bear country in Hudson Bay. Denmark is at the same latitude as parts of Alaska. The main thing keeping these areas relatively warm are surface ocean currents, and the air blowing east off of them. It's one of the major reasons that the term has become "global climate change" instead of "global warming."

At the moment, I think the consensus is optimistic about all this, because it has recently been pointed out that previous simulations which showed the currents shutting down entirely did not take into account prevailing wind patterns.

It's a cautionary note that mirrors one of Schneier's Laws - Any person can design a climate simulation or theory that they are unable to detect flaws in.