70s in November? What fall warming means for Maine

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Final Saturday was the warmest it has been in Augusta in any November since record-keeping started — 76 levels Fahrenheit, like a Maine seaside day two weeks from Thanksgiving, or like a typical November excessive in elements of California or Texas. Portland also set a November record of 75 on Saturday. After a fast dip into what felt like actual fall round Election Day, a lot of the state was again into the higher 60s on the finish of the week, about 20 levels above regular.

Maine is one in every of many locations that claims the adage, “For those who don’t just like the climate, wait 5 minutes.” We’re used to some variability — however local weather change is growing it, supercharging our climate with power as people’ fossil gasoline emissions lure warmth within the environment and heat the oceans. And right here, as we noticed this week, these new extremes are largely tending towards heat.

Alix Contosta, a analysis assistant professor on the College of New Hampshire, research the results of winter warming. I’ve talked to her earlier than about unseasonable heat in, say, January, or the results of accelerating freeze-thaw cycles in early spring. However what about fall warming? I requested Contosta and different scientists what folks must be interested by throughout climate occasions like this.

“In a nutshell, we now have seen temperatures this heat earlier than at the moment of yr,” Contosta wrote to me. “But late autumn ‘warmth waves’ are uncommon. … The implications for ecosystems should not well-understood as we’re experiencing novel situations with out a lot historic precedent.”

Sean Birkel, Maine’s state climatologist and a analysis assistant professor on the College of Maine, defined a few of what’s occurring when temperatures spike into the 70s in early November. In an interview this week, Birkel mentioned a trademark of local weather change in our area is a lengthening summer time season that extends additional into historic fall, shrinking down the coldest stretches of winter.

Birkel used his state local weather knowledge dashboard to point out me how this week’s heat climate stacks as much as this development. This knowledge exhibits Maine has gotten 3-4 levels Fahrenheit hotter on common year-round since 1901. The change is especially pronounced in shoulder months like September and November. And all of Maine’s warmest falls on document have been prior to now 10 years.

On a chart exhibiting each day temperatures and norms for this yr in Bangor, Birkel identified how the latest excessive temperatures all pushed solidly into above-normal territory. One heat day by itself might have had much less of an impact on cold-adapted ecosystems than a collection like we noticed this week, he mentioned.

He underlined in a single day temperatures as a key local weather sign — extra humidity in the course of the day traps extra warmth that doesn’t burn off at evening and sticks round.

“It’s this general improve within the accumulation of warmth that the pure programs are responding to,” Birkel mentioned.

One purpose for the change lies in Arctic sea ice. This northern sea freezes and partially thaws all year long as seasons change. Its frozen space is at its smallest in September earlier than refreezing begins heading into winter. It’s that refreezing course of that drives Maine winters, Birkel mentioned — as new ice varieties, the air transferring over it chills and heads all the way down to us, bringing on the chilly seasons.

The warming local weather means slower ice formation and extra melted space to cowl, inflicting an extended, extra unsettled autumn wait earlier than winter actually units in and leaving openings for heat spikes like this week’s.

Birkel mentioned sea ice has been at a “new low regular” for about 15 years. And proper now, the North Atlantic and Gulf of Maine occur to be experiencing a warmth wave, pushing into document territory on the heels of one other record-warm autumn in 2021, because the Gulf of Maine Analysis Institute reported.

“The local weather system is all the time attempting to achieve a brand new equilibrium,” Birkel mentioned. “Modifications within the Arctic are linked to the modifications within the oceans, and in the end, we really feel that right here in Maine… by these modifications within the climate.”

There’s plenty of variability in the way in which this impacts Northern ecosystems, the timing of seasonal modifications and the way in which these modifications are expressed in nature, which is called phenology. Jay Wason, an assistant professor in UMaine’s Faculty of Forest Sources, mentioned bushes usually are primarily tuned to day size, not temperature, to set off their transitions to winter. However he mentioned later falls and hotter winters do have ripple results for the timing of forests’ spring leaf-out.

“Vegetation can sense the quantity of chilly climate they’ve skilled and solely provoke spring phenology after they’ve skilled sufficient chilly,” Wason mentioned. “So, hotter winters may very well delay spring phenology for a few of our native bushes and extra southerly species with decrease chilling necessities could also be higher in a position to benefit from heat springs.”

Plus, he mentioned, heat fall climate is a photosynthetic boon to invasive species like buckthorn. Birkel additionally identified how disease-carrying ticks are getting a lift to their life cycles and survival charges from hotter falls and winters.

UNH’s Contosta provided one other speculation, although she mentioned she mentioned she’d want to check it in knowledge to show it: “I’m guessing that soil microbial exercise has elevated dramatically in the course of the latest fall warming occasion,” she wrote. “The leaves have largely fallen from the bushes, and all this recent litter is sort of a large buffet to decomposer organisms dwelling on high of or throughout the soil,” particularly in heat, moist situations like this week’s, she mentioned.

“Usually soil nutrient and carbon biking would decelerate at the moment of yr as temperatures cool. I hypothesize that over the previous week, we would see an reverse phenomenon, the place soil microorganisms are tremendous energetic, and charges of soil carbon and nutrient biking are elevated,” she mentioned. “That is carbon which may have been saved in soil however is now within the environment the place it could act as a greenhouse gasoline.”

These are just some examples of how a brief spell of unseasonable heat, or a couple of levels of warming over a protracted interval, can have destabilizing ripple results all through Maine’s delicate ecosystems — to say nothing of significant points like foliage, hibernation, migration, agriculture or the water cycle, or results on human programs like power utilization, heating, infrastructure. These growing spikes within the climate that Maine is constructed round add up, baking in modifications that will persist even after, or if, folks begin to do extra to decrease emissions.

To learn the complete version of this text, see Local weather Monitor: 70s in November? What fall warming means for Maine.

Annie Ropeik has been given the keys to the Local weather Monitor e-newsletter whereas its common writer, the Monitor’s environmental reporter Kate Cough, is on depart. Attain Annie with story concepts at: aropeik@gmail.com.