The 2004 disaster movie “The Day After Tomorrow” depicted the cataclysmic effects—superstorms, tornadoes and deep freezes— resulting from the impacts of climate change. In the movie, global warming had accelerated the melting of polar ice, which disrupted circulation in the North Atlantic Ocean, triggering violent changes in the weather. Scientists pooh-poohed the dire scenarios in the movie, but affirmed that climate change could indeed affect ocean circulation—could it shut down the Gulf Stream?