From a warm January to a frigid February: ‘Global weirding’ could be another signal of climate change

Many small icicles have frozen on a rusty pipe in the street in the winter. (Александр Коновалов/Adobe Stock)Александр Коновалов - stock.adobe.com

INTO THE RED: Climate and the fight of our lives

New England is preparing for a frigid weekend. Much of the region will likely see the mercury plummet into the single digits by Friday evening, and to below-zero temperatures overnight. Saturday could be slightly warmer but highs are expected to stay at 15 degrees or lower.

The cold may break records. The lowest temperature ever recorded for the date on Saturday, set back in 1886, was minus 2. If temperatures fall a bit lower to minus 10, it would be the coldest reading recorded since January 1957. And if the wind chill drops to 30 below zero, which is likely, it will be only the seventh such time Boston has hit that mark since 1940, said Glenn Field, meteorologist at the National Weather Service’s Boston office.

Temperatures like this can be shocking, even for stoic New Englanders — especially when they follow weeks of relative warmth. In Boston, it was the fourth-warmest January since record-keeping began in 1943; just this past Saturday, it was a balmy 50 degrees. In comparison, instances of extreme cold can be all the more disturbing.

“Like a frog in boiling water, we get used to warmer winters,” said Katharine Hayhoe, a renowned atmospheric scientist who serves as chief scientist for the nonprofit Nature Conservancy and is a member of the climate advocacy group Science Moms. “So when we have a flashback to the way winter used to be 30 or 40 years ago, it can come as a shock.”

This fluctuation between weather extremes — or “weather whiplash,” as scientists call it — is becoming all the more common due to climate change.

“When you say global warming, everybody expects us to be warm ever all the time, but what’s really happening is that our weather patterns are being disrupted overall and we’re seeing more variability,” said Hayhoe. “That’s why I often refer to what we’re seeing as ‘global weirding.’”

Bigger oscillations in temperatures can pose problems, causing leaf and tree buds to flower too early and then die in frosty temperatures soon after and throwing off animals’ eating, mating and migration patterns.

This doesn’t mean this winter’s rapid fluctuation is definitely attributable to climate change. After all, climate refers to long-term weather trends.

“All of the watches and warnings that you’re seeing now around this weekend’s cold weather is really in the weather timescale, not the climate timescale,” said Ellen L. Mecray, regional climate services director for the eastern region at the National Oceanic and Atmospheric Administration.

But on a larger time scale, there are signs that erratic weather is becoming more common. One reason: The Arctic is warming quickly — nearly four times faster than the rest of the world, studies show, and arctic winds have a strong impact on global weather patterns.

“Research does suggest that as the climate (and especially the Arctic) continues to warm, we should see more cases in which persistent weather conditions abruptly shift to very different ones,” said Jennifer Francis, senior scientist with the Woodwell Climate Research Center. That includes, she added, not just rapid fluctuations in temperature, but also in precipitation, as seen in California’s swift shift from drought to floods last month.

Scientists are working to demystify the link between climate change and both extreme cold and temperature fluctuations. One factor they’re researching: changes in the jet stream, a band of strong east-to-west winds that direct and energize weather systems.

The jet stream forms between cold air in the north and warm air in the south; when air of two different temperatures meets, the warm air rises while the cool air sinks, creating winds. When the temperature difference between the north and south is especially large, the jet stream can get supercharged and bend and kink rapidly. But as the Arctic warms, the difference between temperatures there and those in mid latitudes is decreasing, which might also make weather shifts more erratic. Like a river, a slower-moving jet stream might be more likely to meander, said Hayhoe.

“If a river is running straight down the side of the mountain, it’s usually going dead straight from point A to point B in a straight line. But if a river is on a plain and gravity isn’t pulling it down, it meanders in big loops and waves,” she said. Scientists are looking into the degree to which this is taking place.