The Day After Tomorrow

The planet is warming up and as the ice caps melt, the great currents of the oceans shift and the Northern Hemisphere is plunged into a new ice age. One scientist has the key to turning back the clock of global warming. But as Western civilisation succumbs to blizzards and tidal waves and the population of the Northern hemisphere begins a mass exodus south, mankind's only saviour is making a lonely, terror-filled trip north.
To a New York disappearing under snowdrifts hundreds of feet high. The city where his son was last heard of.