by Much of the United States is shivering in the brutal cold, while most of the rest of the world is feeling unseasonably warm. Oddly enough, that contradiction fits neatly into explanations for what climate change is doing to Earth, the scientists said.
On a map of global temperatures over the past few days, large areas of the world (the Arctic, Asia, parts of Africa, the Middle East and South America) are shown in dark red, meaning more than a dozen degrees Fahrenheit (7 Celsius degrees). warmer than the late 20th century average. But America sticks out like a cold thumb: a deep blue-purple that’s just as out of control but a little icy.
Wind chills in parts of North Dakota reached minus 70 degrees (minus 56 degrees Celsius), while the heat index in Miami was more than 160 degrees warmer at 92 (minus 33 degrees Celsius). The fourth-coldest NFL football game took place in Kansas City, while around the world the thermometer reached a scorching 92 degrees, 12 degrees (6.8 degrees Celsius) warmer than average on Friday during the Open of Australian tennis in Melbourne. Warm temperatures overnight were recorded in Aruba, Curacao, parts of Argentina, Oman and Iran.
When the weather was warmer than usual, it occurred in both the southern hemisphere, which is summer, and the northern hemisphere, which is winter. For example, Oman in the north had its warmest January night ever at 79.5 degrees (26.4 degrees Celsius). Argentina, in the south, had a record warmest night in January at 81.1 Fahrenheit (27.3 Celsius).
If it seems like the world has turned upside down, in some ways it has. Because all of this comes from what’s happening in the Arctic, where it used to warm twice as fast as the rest of the planet. Now it is heating up three or four times faster.
“When the Arctic is incredibly warm (like it is now), we’re more likely to see frigid cold encroach on places like Texas that aren’t well equipped to deal with it,” said Jennifer Francis, a climate scientist at the Woodwell Research Center. and pioneer in the theory of Arctic Amplification, which links cold outbreaks to climate change. “Rapid warming of the Arctic is one of the clearest symptoms of human-caused climate change, making winter extremes more likely even as the planet warms overall.”
The way the cold is encroaching is through a weather phrase that’s increasingly familiar to Americans: the polar vortex. It is a meteorological term that dates back to 1853, but has only been used frequently in the last decade.
That could be because ice spikes are happening more frequently, said winter weather expert Judah Cohen of Atmospheric Environmental Research, a commercial firm outside Boston.
The polar vortex is strong, frigid weather that typically lingers over the top of the planet, locked in by strong winds that whip around it, Cohen said.
It’s like an ice skater spinning quickly with her arms bent, he said. But when the polar vortex weakens, her arms begin to flail, the skater slips, and “all the cold air is released from the center of the polar vortex,” Cohen said.
The current cold outbreak is consistent with the Arctic shift and the polar vortex, Cohen said. “What we found is that when the polar vortex is stretched like a rubber band, extreme, severe winter weather is much more likely to occur in the United States. “That’s where it tends to focus and in January we will have an extreme case of that stretching of the polar vortex.”
This one is stronger and can last longer than most, Cohen said.
Cohen and others have conducted studies showing that polar vortex outbreaks have become more frequent in recent decades.
The idea is that the jet stream (the upper air circulation that drives climate) is more undulating in amplified global warming, said University of Wisconsin-Madison climate scientist Steve Vavrus. And those upper-air wave changes knock the polar vortex out of place and toward the United States, Cohen said.
It is a theory still debated by climate scientists, but increasingly accepted. Initially, Vavrus and Francis theorized that it was due to melting Arctic sea ice, causing changes in barometic pressure. Now, several scientists say it’s more complicated, but it’s still linked to climate change and supercharged warming in the Arctic, with other factors like the Siberian snowpack and other atmospheric waves also playing a role.
“The key takeaway for me right now is that Arctic amplification is happening and has complex interactions within our climate system. Winter will always bring us cold weather, but like the warm season, it may be changing the ways we understand and the ways we are still learning,” said Marshall Shepherd, professor of meteorology at the University of Georgia. “Unlike the Las Vegas slogan, what happens in the Arctic doesn’t stay in the Arctic.”
Think of what’s happening as an orchestra composing a symphony, and “what’s driving all those instruments in the orchestra is a warming planet,” said Victor Gensini, a meteorology professor at Northern Illinois University.
Gensini and Cohen said this cold snap in the United States will disappear in several days to be replaced by unusually warm weather, due to climate change. But it looks like another polar vortex will arrive at the end of the month, although not as strong as this one, they said.
Despite the American cold, the Earth’s global average temperature continues to break daily, weekly and monthly records, as it has for more than seven months. That’s because the United States occupies only 2% of the Earth’s surface, scientists said.
“A place like Chicago, Denver or Lincoln, Omaha, Oklahoma City, Dallas, Houston, I mean, we’re all experiencing it,” said Gensini, who said the temperature outside his window on Tuesday was 6 degrees below zero. “We are an isolated pocket if you look globally.”
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