“The unusual weather we’re seeing this winter [2017-18] is in no way evidence against climate change,” Dr. Michael Mann explained to Climate Reality . “It is an example of precisely the sort of extreme winter weather we expect because of climate change.” Why is this happening? The short answer, at least in part: it’s about the jet stream. While the scientific community is still investigating the intricacies of the phenomenon, a growing body of research indicates that as global temperatures rise and the Arctic continues to warm, the jet stream is both slowing and growing increasingly wavy, allowing bone-chilling cold Arctic air to both spill much farther south than usual and linger over areas unaccustomed to it for longer. Learn More: The 12 Questions Every Climate Activists Hears 16