Upper Midwest Locked In Dangerous Cold Snap

Excerpt from this article:

An elderly Chicago woman was the latest victim to succumb to the wicked weather. She died from hypothermia after being found outside wearing a coat and shoes just steps from her back stairs on the city's northwest side. She was the eighth person to die from the cold so far this season in Chicago.

Can someone remind me again why we're supposed to think that the Earth's temperature is currently too high?