What is the exposition?

The film begins by telling the story of an attempt to counteract global warming by engineering climate patterns with a chemical called CW7. The plan backfires and causes an Ice Age, which kills all life on earth except for the people who live on the Snowpiercer, a perpetual motion train that travels a span of track that loops one time around the globe in a year. It was created by a business magnate named Wilford, who runs the train.