The recent record breaking cold weather in the eastern U.S. is likely exacerbated by global warming. Here is why.

While the temperatures in the Arctic are still very cold, they have warmed almost twice as much as the rest of the Earth due to climate change. In order to understand what is going on, an analogy that may help is to think of a giant mound of cold air centered on the North Pole. The colder the air, the taller and steeper the mound. As the Arctic has warmed, the mound has flattened somewhat.

Now think of the jet stream (which shows up on most weather reports) as a closed loop river circling around the Earth, centered at the North Pole. The jet stream acts as a guide for high and low pressures.

The jet stream usually has ripples as it moves around the Earth. As the Arctic warms, the more flattened mound of cold air allows the jet stream to more easily meander, like rivers in flat areas. As the jet stream meanders get bigger, they can extend farther south ( or north ) allowing warm air and Arctic air to follow it into regions where they rarely go. The larger jet stream meanders can sometimes produce an “Omega Block,” which is a combination of two low pressures and a high pressure. As the jet stream goes south of the low pressures (on each side of the high pressure) and north of the high pressure, it creates a shape like the Greek letter omega.

Omega blocks are often very stable and can last for weeks. In the last of December and the first of January there was a very stable omega block in the United States with a low pressure in the Pacific (the jet stream below it), a high in the western U.S. (the jet stream above it) and a low in the eastern U.S. (the jet stream below it) allowing the extreme cold to go deep into the south.

Omega blocks have become more common as the meanders of the jet stream have become larger. They have also played a part in the extreme heat experienced in summers in Alaska because they can also bring very warm air farther north.

With a warmer Arctic, larger meanders in the jet stream, and the occasional omega block we get weather patterns that are more extreme and tend to last longer.

The basic meteorology here is what is taught in junior high earth science combined with my more than 40 years of studying climate change. There is little or no controversy about this basic information. My goal here is communicate with an analogy to make this more easily understandable.

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