At least 20 people have died and vast swaths of the US Midwest and Northeast have come to a standstill because of a frigid blast of sub-zero temperatures. Another Arctic vortex has struck.

A polar vortex is a large expanse of swirling, cold air that is usually located in the polar regions. However, during winter, and now more frequently due to human-caused climate disruption, the vortex expands and moves southward, bringing the Arctic temperatures with it.

Studies have shown that a warming Arctic is shifting the jet stream, and playing a critical role in the changes that are causing the…