If the Earth is warming, why does it still get so cold? When winter comes in the northern hemisphere, the Sun goes down over the Arctic and the North Pole. That region cools. It might take a little longer to cool than it did when we had less carbon dioxide, but it, still, gets cold.

Air becomes isolated in a cold pool.  The jet stream, a river of air, strengthens around the edge of a cold pool. If that cold pool, then, gets pushed away from the Arctic and settles over the United States, for a while, we experience periods of very cold weather. In news articles and commentaries, we have come to know this as “the vortex.”

January 2, 2024: Here is an article on my website that discusses a predicted 2024 cold snap and just what does normal mean in a changing climate.

2024 Cold Snap in the Eastern U.S.

And just as a reminder, though it still gets cold, winter is the fastest warming season. Another topical collection:

Warming Winter Syndrome

 

Here are some of my pieces on the subject.

January 8, 2025: Don’t let these temperatures fool you: The extreme winters of the past are gone | Opinion Detroit Free Press

January 6, 2025: That Arctic blast can feel brutally cold, but how much colder than ‘normal’ is it really?  The Conversation (Republished January 18, 2025)

February 8, 2019: Making sense of the polar vortex and record cold on a feverish planet. Washington Post

December 12, 2016: WEMU radio interview on cold air event.

 

Video: Why Is It So Cold?


Video: It Still Gets Cold

 

Written Explainers:
In a series of blogs on Wunderground.com, I wrote about the “Arctic oscillation” and the ”polar vortex.” I try to find ways to talk about these in a way that make sense to those who are not formal students of weather and climate. Within these blogs are links to many other resources.
(Because of changes to the Wunderground.com archive, some of the internal links are forever broken.)
  1. Some background information and definitions.
  2. The Arctic oscillation is often related to very cold winters.
  3. The polar vortex forms in the winter, and how cold air becomes isolated.
  4. Why the isolated pool of cold air wobbles around.
  5. Why we think the behavior of the Arctic oscillation is changing as the Earth warms.
  6. A late 2013 review of the scientific investigation into changes in the Arctic oscillation.
  7. Are changes in the Arctic changing weather in the continental U.S.? (Background, 2014)
  8. Are changes in the Arctic changing weather in the continental U.S.? (Analysis, 2014)

 

Here are some questions relevant to climate change:

A pool of cold air forms over the Arctic in the winter. As the Earth warms, this cold pool might get smaller or not last as long, but it still forms in the polar night. The Earth’s atmosphere and oceans move heat around, and they carry heat from tropics to the poles. When there are episodes of high heat transport, we expect warm air to move towards the pole and to push the cold pool away from the pole. In the Northern Hemisphere, sometimes this air is pushed towards the United States, sometimes towards Europe or Siberia.
  • Is the cold pool getting smaller?
  • When there is warm air pushed up towards the North Pole, is that air getting warmer from decade to decade?
  • Is the cold air displaced over the United States getting colder from decade to decade?
  • Are we seeing more frequent episodes of it being warm in the Arctic during winter


Richard B. (Ricky) Rood, Climate and Space Sciences and Engineering (CLaSP)