A lot of wild weather has afflicted North America this year: deluges in Colorado and Alberta, a heatwave in Alaska, and bitter cold in Florida. But there's a high-altitude link between each of these unusual events which itself might be tied to climate change: erratic behavior by the polar jet stream.
This famous current of air zips eastward at high altitudes from the continent's West, normally passing over North America somewhere near Seattle. It is one of two jet streams in the Northern Hemisphere -- the other being the subtropical jet stream. Together, these powerful currents have long held weather patterns in their normal places, one year after another. But something weird is going on up there.
The normally direct polar jet stream has been swinging wildly this summer, dipping north and south like the line graph on a U.S. jobs report. At times it splits in two. From Popular Mechanics:
The jet stream is a year-round feature of our atmosphere, but the double jet stream phenomenon is more common in winter. When it shows up in the summer, watch out.