Much of the United States is shivering in brutal cold, while most of the world is experiencing unusually warm weather. As strange as it may sound, that contradiction fits neatly into the explanations of what climate change is doing to the Earth, scientists say.
On a map of global temperatures over the past few days, large parts of the world – the Arctic, Asia, parts of Africa, the Middle East and South America – appear dark red, which is more than a dozen degrees Fahrenheit (7 degrees Celsius). ) means. warmer than the late 20th century average. But the United States stands out like a cold thumb – a deep blue-purple that is just as out of place, but on the icy side.
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 degrees (33 degrees Celsius). The fourth-coldest NFL football game took place in Kansas City, while the thermometer around the world reached a sweltering 92 degrees on Friday during the Australian Open in Melbourne, 12 degrees (6.8 degrees Celsius) warmer than average. Hot temperature records fell overnight in Aruba, Curacao, parts of Argentina, Oman and Iran.
Where the weather was warmer than normal, this happened both in the Southern Hemisphere, which is in summer, and in the Northern Hemisphere, which is in winter. For example, Oman, in the north, had its warmest January night on record at 79.5 degrees (26.4 degrees Celsius). Argentina, in the south, had a record for the warmest January night at 27.3 degrees Celsius.
If it seems like the world has turned upside down, in a sense it has. Because this all stems from what’s happening in the Arctic, which used to warm twice as fast as the rest of the planet. Now it heats up three to four times faster.
“When the Arctic is unusually warm (as it is now), bone-chilling cold is more likely to creep into places like Texas, which are ill-equipped to deal with it,” said Jennifer Francis, a climate scientist at the Woodwell Research Center. and a pioneer in the theory of Arctic Amplification, which links cold outbreaks to climate change. “The rapid warming of the Arctic is one of the clearest symptoms of human-induced climate change, making winter extremes more likely even as the planet warms overall.”
The way the cold gets in is through an aversion that is becoming increasingly familiar to Americans: the polar vortex. It is a weather term that dates back to 1853, but has only become widely used in the last ten years.
That could be because the icy bites are becoming more common, says winter weather expert Judah Cohen of Atmospheric Environmental Research, a commercial firm outside Boston.
The polar vortex is strong, frigid weather that usually stays above the top of the planet, trapped by strong winds that blow around it, Cohen said.
It’s like a skater spinning quickly with her arms tucked in, he said. But when the polar vortex weakens, the arms start to swing outward, the skater slips and “all the cold air is released, away from the center of the polar vortex,” Cohen said.
The current cold outbreak is consistent with changes in the Arctic and the polar vortex, Cohen said. “What we found is that when the polar vortex stretches like a rubber band, extreme winter weather is much more likely in the United States. That’s where it’s usually concentrated and in January we have an extreme case of the polar vortex stretching.”
This one is stronger and may last longer than most, Cohen said.
Cohen and others have conducted studies showing that polar vortex outbreaks have become increasingly common in recent decades.
The idea is that the jet stream — the upper air circulation that drives the weather — will be more undulating as global warming intensifies, says climate scientist Steve Vavrus of the University of Wisconsin-Madison. And those wave changes in the upper air knock the polar vortex out of place and toward the United States, Cohen said.
It’s a theory that is still debated by climate scientists, but is increasingly accepted. Initially, Vavrus and Francis theorized that this was due to the melting of the Arctic sea ice, which led to changes in barometric pressure. Now several scientists say it is more complicated, but still linked to climate change and global warming in the Arctic, with other factors such as Siberian snow cover and other atmospheric waves also playing a role.
“The most important conclusion 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 can change the ways we understand and ways we are still learning about,” said Marshall Shepherd, professor of meteorology at the University of Georgia. “Contrary to the Vegas slogan, what happens in the Arctic doesn’t stay in the Arctic.”
Think of what happens when an orchestra makes one symphony, and “what’s powering all those orchestral instruments is a warming planet,” said Victor Gensini, a professor of meteorology at Northern Illinois University.
Gensini and Cohen said this cold snap in the United States will disappear within days and 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, Earth’s average temperature continues to flirt with daily, weekly and monthly records, as it has for more than seven months. That’s because the United States covers just 2% of the Earth’s surface, scientists say.
“A place like Chicago or Denver or Lincoln, Omaha, Oklahoma City, Dallas, Houston, I mean, we’re all experiencing it,” said Gensini, who said the temperature outside his window was 6 degrees Celsius on Tuesday. “If you look globally, we are one isolated group.”
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