By Brian K Sullivan
With just weeks left to go, the world is heading toward the warmest winter ever recorded as a strange brew of weather patterns at the top of the world combines with the mercury-boosting influence of climate change.
A stubbornly extreme low-pressure system over the North Pole has pulled the jet stream north, backing it up against the fast-moving winds that constantly ring the polar region. The result: A tight barrier that’s kept the cold locked in place, upsetting fall forecasts for an icy winter ahead.
Now, with temperatures 3° Celsius higher than the 20th century average across the contiguous U.S., the uniqueness of the pattern is expected to spark an avalanche of new research into its cause. If the trend continues through Feb. 29, when winter ends for meteorologists, it will set a global high for the season in U.S. records going back 141 years.
“What really jumps out is not a particular hot spot,” said Bob Henson, a meteorologist with the Weather Underground, an IBM company. “But the sheer breadth of the warmth.”
Last month marked the hottest January ever in Europe, according to the Copernicus Climate Change Service, with surface temperatures 3.1° C warmer than average. It was 5° C milder across much of Russia and parts of Scandinavia and eastern Canada, according to the U.S. National Centers for Environmental Information.
It wasn’t supposed to turn out this way. Throughout the fall, it looked as if the Arctic would release its cold normally. Both AccuWeather Inc. in Pennsylvania and Maxar, a Maryland-based commercial forecaster, predicted this year’s winter would be colder than the last one, suggesting that U.S. heating costs would likely be elevated.
“But it simply didn’t pan out that way,” said Ryan Truchelut, the president of Weather Tiger LLC in Tallahassee, Florida, which provides forecasts for the agriculture industry. “A lot of existing forecasting methods didn’t capture this.”
While the pressure system—dubbed the “Arctic oscillation”—tends to swing back and forth between low and high pressure, strengthening and weakening the surrounding polar winds, meteorologists say it’s rarely this intense and its hold rarely lasts this long.
It’s a mystery that will lead to new research on why it happened, and if it’s directly related to climate change given the fact that it comes at a time when the four warmest Januaries on record have all occurred over the last four years. The one upside to this winter is that it has allowed the Arctic to gain back some of its sea ice, which has been shrinking in recent winters.
“We are still in the early days of an evolving climate era,” Henson said. “The climate will keep changing under our feet as we try to get our arms around it.”
As the sun sets on the Arctic and darkness settles over the North Pole, a deep reservoir of frigid air builds up across the region. Normally, the pressure system sitting directly over the pole will swing back and forth between high and low pressure, strengthening and weakening the surrounding polar winds. When they’re at their weakest, the cold escapes.
But not this year. The Arctic oscillation reached record intensity on Feb. 10, and will likely increase in strength in the next few days, said Craig Long, a meteorologist with the U.S. Climate Prediction Center in College Park, Maryland.
The oscillation is rarely this intense, and its hold rarely lasts this long. Temperatures will be colder than average on Friday, according to the U.S. National Weather Service. But the mercury will once again rise significantly above average starting on Feb. 22, and continuing through at least another week.
In New York, some plants are already pushing up through the Earth, convinced that spring has sprung, while many southern states have seen sprouted leaves three weeks early in many places. Meanwhile, the mild readings depressed energy consumption and prices.
New Yorkers probably reduced heating costs about 10.6% from a year earlier, according to AccuWeather. Philadelphia had a similar savings while Washington likely cut bills by 11% and Boston 11.1%.