After years of unabated global warming, the greenhouse effect is wreaking havoc all over the globe in the form of catastrophic hurricanes, tornadoes, tidal waves, floods and, most ominously, the beginning of the next Ice Age. Paleoclimatologist Jack Hall tries to save the world while also shepherding to safety his son Sam, who was in New York when the city was overwhelmed by the beginnings of the new big freeze.…