By SETH BORENSTEIN (AP Science Writer)
Throughout much of America, and particularly in the normally cold north, the country experienced a winter without, well, winter.
In places like Burlington, Vermont, and Portland, Maine, known for their cold winters, the temperature never dropped below zero. Minnesota referred to the last three months as “the lost winter,” warmer than the infamous “year without a winter” in 1877-1878. Michigan, where mosquitos were biting in February, offered disaster loans to businesses affected by the lack of snow. The Great Lakes saw record low levels of winter ice, with Erie and Ontario being “essentially ice-free.”
In a large part of the country from Colorado to New Jersey, and Texas to the Carolinas, the arrival of spring leaves is three to four weeks earlier than the 1991-2020 average, according to the National Phenology Network, which tracks the timing of plants, insects, and other natural signs of the changing seasons.
“Long-term warming combined with El Nino caused winter to not appear in the U.S. this year,” explained Yale Climate Connections meteorologist Jeff Masters, who co-founded the private firm Weather Underground. Masters mentioned being bitten by a mosquito in Michigan this year, which he found unbelievable.
The National Oceanic and Atmospheric Administration confirmed on Friday that the 2023-2024 winter was the warmest in almost 130 years of record-keeping for the United States. The Lower 48 states averaged 37.6 degrees (3.1 degrees Celsius), which is 5.4 degrees (3 degrees Celsius) above the average.
This is just the latest in a series of broken temperature records, both national and global, primarily due to human-caused climate change from the burning of coal, oil, and gas, according to scientists.
And it was the warmest U.S. winter by a significant margin. The past three months were 0.82 degrees (0.46 degrees Celsius) warmer than the previous record set eight years ago, which “is a pretty good leap above the previous record,” said Karin Gleason, chief of monitoring at NOAA’s National Centers for Environmental Information.
Last month was only the third-warmest February on record. However, Iowa surpassed its warmest February by 2 degrees, while parts of Minnesota were 20 degrees warmer than the average for all of February, Gleason noted.
On Feb. 11, Great Lakes ice cover hit a February record low of 2.7%.
A strong area of high pressure led to warm and dry conditions in the eastern United States, while California continued to experience atmospheric rivers, she explained.
The European climate agency Copernicus stated earlier this week that it was the warmest winter globally, mostly due to climate change with an added boost from a natural El Nino, which affects weather worldwide and provides additional heat.
In the past 45 years, winter has warmed more quickly in the United States than globally, with winters in the Lower 48 states now averaging 2.2 degrees (1.2 degrees Celsius) warmer than in 1980, according to an analysis of NOAA data by The Associated Press.
This is likely because land warms up faster than the ocean, and much of the United States is land whereas most of the globe is ocean, Gleason mentioned.
In the United States, the speed of extra warming has slowed down since 2000 according to NOAA data. Judah Cohen, an expert on winter weather, believes that this is due to Arctic Amplification, which is the way climate change has caused the Arctic to warm up three to four times more than the rest of the world and seems to change weather patterns further south.
As the Arctic warms up more quickly, the jet stream — which carries weather systems around the Earth — becomes unsteady and weaker. This means that the cold air held at the top of the planet, known as the polar vortex, escapes from its usual area and drifts elsewhere, leading to short periods of very cold air that briefly counteract the overall warming trend in certain places, Cohen said.
In January, the polar vortex briefly moved away and had a small impact on winter temperatures in the Lower 48, Cohen said. However, for most of the year, when the polar vortex shifted, it affected Europe or Asia with bursts of very cold air, rather than the United States, so there was no offsetting effect on winter temperatures in America, he said.
This year, Boston didn't even experience single digit temperatures, with the lowest temperature of the winter being 14 degrees, a record for lack of extreme cold.
And as for snow? Forget about it, at least in the east and north.
In Fort Kent, located in far northern Maine, an annual dog sled race was canceled due to the lack of snow. The town had received 46.8 inches (119 cm) of snow this year by last week, just over half of the usual amount, according to the National Weather Service.
The snow cover in the United States in February was the second lowest on record and the third lowest in December, with only January being above the normal amount, according to the Rutgers Snow Lab.
Warm winters have consequences, said Theresa Crimmins, director of the National Phenology Network.
“Warm winters can also lead to earlier, longer, and more abundant pest seasons, because populations weren’t knocked back by cold,” Crimmins said in an email. “Additionally, the allergy season can worsen — starting earlier, lasting longer, and resulting in more pollen in the air.”
Due to the warmer weather, trees and flowers may bloom earlier. The cherry blossoms in Washington are expected to peak about two weeks earlier than they did in 2013. Early blossoming can disrupt the careful timing with pollinators and birds.
“Many of the birds that migrate south for the winter use day length as a signal to come north in the spring,” Crimmins stated. “In years like this one, where plant and insect activity is signaled to start much earlier than usual, the birds may miss out on the best time for food by arriving too late.”
But there is some good news for California with atmospheric rivers and snowstorms likely to rebuild snowpacks and fill in reservoirs that had been dangerously low until a couple years ago, Gleason said.
Cohen, who is an expert on winter weather and works outside of Boston, humorously claimed that the U.S. no longer has four seasons: “We have two seasons. We have summer and we have November.”
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Writer Patrick Whittle contributed to this report from Portland, Maine for the Associated Press.
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For more information on AP’s climate coverage, visit http://www.apnews.com/climate-and-environment
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Follow Seth Borenstein on X at @borenbears
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