The movie opens with Jack Hall (Dennis Quaid) in Antarctica with two colleagues, Frank and Jason (Jay O. Sanders and Dash Mihok), drilling for ice core samples on the Larsen Ice Shelf for NOAA. The ice shelf breaks off from the rest of the continent and Jack almost falls to his death. Jack presents his findings on global warming at a United Nations conference held in New Delhi, India, where diplomats from several countries including the Vice-President of the United States (Kenneth Welsh) are unconvinced by Jack's theory.
The idea, however, resonates with Professor Terry Rapson (Ian Holm) of the Hedland Climate Research Centre in Scotland. Two buoys in the North Atlantic simultaneously show a massive drop in water temperature, and Rapson concludes that the melting of the polar ice has begun to disrupt the North Atlantic current. He calls Jack, whose paleoclimatological weather model holds reconstructional data of the palaeoclimate change that caused the first Ice Age, to predict what will happen and when. Jack believed that the events would not happen for many years in the future; but he, Frank, Jason, and NASA's meteorologist Janet Tokada (Tamlyn Tomita) build a forecast model with his, Rapson's, and Tokada's data.
Soon after, across the world, violent weather causes mass destruction and chaos. A hail storm with football-size hailstones devastates Tokyo, Japan. A outbreak of tornadoes all over Los Angeles devastates the entire area including Los Angeles International Airport. The U.S. President (Perry King), authorizes the FAA to suspend all air-traffic over the United States due to severe turbulence, and an Avianca Boeing 707 plummets. As three RAF helicopters fly en route to the British Royal Family, they enter the eye of one of three massive hurricane-like superstorms, which causes a phenomenal temperature drop below −150 °F (−101.1 °C) that instantly freezes their fuel lines and rotors, causing them to crash. One of the crew opens a door and is instantly frozen.
Jack's son, Sam (Jake Gyllenhaal) is in New York City for an academic competition with his friends Brian and Laura (Arjay Smith and Emmy Rossum). During the competition, the weather becomes increasingly violent with strong winds and torrential rains. Sam calls his father, promising to be on the next train home. However, the storm worsens even more, forcing subways to close due to flooding and closing Grand Central Station. An enormous tidal wave as high as half of the Statue of Liberty hits Manhattan, putting the island under several feet of water. Sam and his friends barely make it to the shelter of the New York Public Library. Meanwhile in Scotland, Rapson and his co-workers are trapped in their research lab by the deepening snow and the storm. They are last seen drinking scotch as the power supply fails.
Survivors in the Northern US are forced to flee to the Southern and Southwestern United States, with some Americans illegally crossing the border to Mexico. After advising the EOP of plans to evacuate half of the country, Jack sets off for Manhattan to find his son, accompanied by Frank and Jason. Their truck crashes into a snow-covered tractor-trailer just past Philadelphia, so the group continues on in snowshoes while connected to one another by rope. During the journey, Frank falls through the glass roof of a snowbound shopping mall. As Jason and Jack try to pull Frank up, the glass under them continues to crack, so Frank sacrifices himself by cutting the rope.
Inside the library, Sam advises everyone of his father's instruction to stay indoors. Few listen, and the small group that remains burns books to keep warm and breaks the library's vending machine for food. Laura is found to be afflicted with severe blood poisoning, so Sam, Brian, and J.D. search for penicillin in a nearby Russian cargo ship that drifted inland, while a homeless man named Caddy who listend to Sam's warnings watches over her. While within the ship, the three are attacked by a pack of hungry wolves that presumably escaped from the Central Park Zoo. The eye of the superstorm begins to pass over the city with its −150 °F (−101.1 °C) instant freeze, and the entire New York skyline is shown to freeze from the top down. The three hurry back to the library with medicine, food and supplies, barely making it to safety.
During the deep freeze, Jack and Jason take shelter in an abandoned Wendy's, then resume their long walk and finally arrive in New York City, passing the frozen and half-buried in ice Statue of Liberty. They find the library nearly buried in a snow drift, but make their way in and find Sam's group alive. They signal for help and are rescued by a group of UH-60 Blackhawk helicopters. As they leave Manhattan, they see people on the rooftops of many buildings with UH-60 Blackhawk and CH-47 Chinook helicopters approaching to evacuate them. The movie ends with two astronauts looking down at the view of the Earth from the International Space Station, showing a majority of the northern hemisphere covered in ice, and a drastic reduction in the pollution content. |