With all the talk of global warming, why did we just experience such incredibly cold weather that reached so far south?

Dear Tom,
With all the talk of global warming, why did we just experience such incredibly cold weather that reached so far south?
— Donna Weck, western suburbs
Dear Donna,
It’s true that the cold spell that just ended shattered records in several locations in the Central, Eastern and Southeastern United States, but it’s winter, after all. However, many locations have been colder in years past than the readings that were recently registered.
“Global warming” is a term defined as the observed and projected increases in temperature of the Earth’s atmosphere and oceans. It considers long-term temperature change, worldwide — and that change is upward. It does not rule out occasional occurrences of spells of record cold. And by the way, the cold spell just ended occurred only in portions of Central and Eastern North America.