This article is written by Jennifer Francis, a research professor at Rutgers University. She receives funding from the National Science Foundation and NASA. She is a member of the American Meteorological Society, American Geophysical Union, Association for Women in Science and the Union of Concerned Scientists: One thing we do know is that the polar jet stream – a fast river of wind up where jets fly that circumnavigates the northern hemisphere – has been doing some odd things in recent years… Rather than circling in a relatively straight path, the jet stream has meandered more in north-south waves. In the west, it’s been bulging northward, arguably since December 2013 – a pattern dubbed the “Ridiculously Resilient Ridge” by meteorologists. In the east, we’ve seen its southern-dipping counterpart, which I call the “Terribly Tenacious Trough.”… This is where climate change comes in: the Arctic is warming much faster than elsewhere. That Arctic/mid-latitude temperature difference, consequently, is getting smaller. And the smaller differential in temperatures is causing the west-to-east winds in the jet to weaken.