In a future where a failed global-warming experiment kills off most life on the planet, a class system evolves aboard the Snowpiercer, a train that travels around the globe via a perpetual-motion engine. – IMDb

So these folks tried to stop global warming and ended up sending the planet into a deep freeze? In the immortal words of Homer Simpson: DOH!
I was sold on already this movie just because of the combo of an interesting story and it being directed by Bong Joon-ho (THE HOST…the Korean monster movie version not the drippy Young Adult novel turned terrible film version) but add Tilda Swinton being a totally evil villain and I am even more eager to see this than I already was. Her “let them eat cake” style verbal smackdown she delivered to the have-nots at the beginning of that trailer was great.