You've seen what a nuclear winter looks like, as imagined by filmmakers and novelists. Now you can take a look at what scientists have to say. In a new study, a team of four U.S. atmospheric and environmental scientists modeled what would happen after a "limited, regional nuclear war." To inexpert ears, the consequences sound pretty subtle—two or three degrees of global cooling, a nine percent reduction in yearly rainfall. Still, such changes could be enough to trigger crop failures and famines. After all, these would be cooler temperatures than the Earth has seen in 1,000 years.

As the flu spread across the U.S. last winter—earlier and more seriously than usual—several computer models were watching. There was Google Flu Trends, which famously went awrythat season. And there was a nameless model, built by researchers at several U.S. universities, designed not only to track how many people have the flu, but also to forecast when flu instances will peak in individual cities across the U.S.