Continuity mistake: The older scientist reaches down to grab Jack with his right hand. In a closeup, Jack grabs the right hand and the same scientist catches him with the left hand as well. In the next shot from above, only his left hand is down, but as he pulls Jack up both hands are on him. (00:05:40)
Chosen answer: Global warming melts the icecaps, releasing millions of tons of fresh water into the oceans. This upsets the delicate environmental balance of the oceans, leading to the ocean currents stopping. It's these currents that carry warm water up into the Northern Hemisphere, causing our temperate climate. The currents stop, everything cools down, fast.
Tailkinker ★