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Warmest winter on record gives way to extra-early signs of spring

UN's "State of the Climate" report
UN releases annual "State of the Climate" report 06:49

If this winter season was not very wintery where you live, you're certainly not alone — that was the experience for most of the people in the Northern Hemisphere. According to NOAA, the winter of 2019-2020 was the warmest on record across all continents north of the equator.

With an average temperature 4 degrees Fahrenheit above the 20th century average, this winter ranks first among the warmest winters on land in the Northern Hemisphere, beating the very mild winter of 2015-2016.


Up until now the 2015-2016 winter was the clear winner for warmth, but now it must split that distinction with this season. When you factor in the ocean surface in addition to land temperatures, 2015-2016 still holds the record. That's because that winter, the Earth experienced a super El Niño, overheating the surface waters of the equatorial Pacific and radiating heat into the atmosphere. It's years like that where record warmth is expected. But there was no El Niño to be found this winter, and yet, at least over land, it impressively still managed to exceed a super El Niño year.

As a result of the unusually warm weather this winter, seasonal rhythms have been thrown off kilter. As CBS News reported earlier this week, in places from Moscow to the U.S. bears have  been seen coming out of hibernation early. Connecticut's Beardsley Zoo says its native black bears emerged in early March — almost a month earlier than usual. 

In much of the eastern United States, spring "leaf out" — the season's first blossoming of several plant species — has sprung more than 20 days early. In parts of the Southeast, this year's spring bloom is the earliest in the 39-year record, according to the National Phenology Network, an organization that studies the impact of climate on nature's cycles.


CBS News asked Dr. Theresa Crimmins, director of the USA National Phenology Network, if such a widespread early arrival of spring is unusual. "Yes," she replied, "this year stands out, because so much of the country is showing such an early spring. Huge swaths of the Southeast have had the start of spring arrive 2-3 weeks and more early."

And the reason behind it? "Climate change is certainly at play — there is a clear trend toward an earlier start to spring," Crimmins said. 

A 2015 study led by Cornell University's Dr. Toby Ault found a regional trend in earlier "leaf out,"  indicated by the orange colors in the map below, by up to 1.6 days per decade due to a warming climate on top of natural fluctuations.

Ault et. al,, 2015

With recent temperatures reaching in the low 70s — 25 degrees above normal — flowers are starting to appear in New York's Central Park weeks early.

Trees blooming in New York City's Central Park on an unseasonably warm day in March 2020. Jeff Berardelli

The early spring is getting a boost from a winter with very little cold and snow in most of the country and around the world. In the U.S., the winter was nearly 4 degrees Fahrenheit above the 20th century average, ranking as 6th warmest since the late 1800s. Washington D.C.'s snowfall was measly — less than an inch — and Boston registered its second-lowest snow total on record.

In the image below, the color brown indicates places that have seen less snow than normal.

The warmth has been even more astonishing in Europe. According to the Copernicus Climate Change Service, Europe just experienced its warmest winter on record by far — 6 degrees Fahrenheit above normal — shattering the old record by 2.5 degrees Fahrenheit.

The warmth caused difficulties for reindeer herding in northern Sweden, the failure of the ice-wine harvest in Germany, and forced organizers to import snow for sporting events in Sweden and Russia. Parts of Russia near Moscow experienced a winter of 10 degrees Fahrenheit above normal.

When viewed over a longer period of time, Europe's record warm winter stands out even more starkly. Compared to normal conditions at the beginning of the Industrial Revolution (1850-1900), before human-caused greenhouse gases started to warm the planet, this winter was a remarkable 8 degrees Fahrenheit above normal across the whole continent.

Copernicus Climate Change Service

Some of the warmer weather in the mid-latitudes of the U.S. and Europe can be explained by abnormally strong polar vortex winds in the Arctic, which lassoed cold air, trapping it far north. These sporadic strong polar vortex patterns are most likely part of a natural cycle. 

However, the broad scale and intensity of overall warmth across the Northern Hemisphere cannot be explained without climate change. Each year more signs emerge that human-caused climate change is playing a bigger role. A peer-reviewed paper published March 10 in the journal Geophysical Research Letters shows the climate-warming signal is becoming more apparent, with "many regions already experiencing a climate which would be 'unknown' by late 19th century standards."

"The speed of climate change is accelerating" says Dr. Peter Gleick, a climate scientist and founder of the Pacific Institute, a sustainability nonprofit in Oakland, California. 

"Sadly, it is not a surprise to most climate scientists. We've seen this coming for literally decades and now it's upon us," said Gleick, "I expect there will be new, hotter temperature records broken over and over again in the future along with increasingly severe droughts and floods, rising sea levels, and worsening fire risks. There's no 'normal' anymore. And still our politicians dither. It's sad and disturbing to me."

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