It’s winter on the Chesapeake. It is getting warmer anyway.

About a month back, I spotted my neighbor Tim Hamilton working after dark in his yard.

He was wearing a headlamp to see, and the sight of a man raking leaves under a powerful spotlight was unusual. Turns out his trees had dropped their cover two weeks ahead of schedule.

“The leaves in this area may vary in intensity of autumnal colors, but they fall like clockwork,” said Tim, who keeps a precise garden journal. “This year they fell exactly two weeks earlier than usual. The drought this summer may have contributed, but our summer droughts are getting longer every year, with only a couple of exceptions.”

Sometimes the signs of a warming planet are obvious: longer summer droughts make the leaves fall early; warmer air makes storms bigger and wetter; rising seas mean sunny-day floods happen more frequently and reach higher. Summers are hotter, and the boundaries between seasons slip.

In winter, which arrived with the solstice at 10:27 p.m. Thursday, it can be harder to spot the signs of a warmer world because, well, it’s cold.

“The entire globe is warming,” said Doug Myers, chief scientist at the Chesapeake Bay Foundation. “In the Southern Hemisphere, it’s their summer when it is our winter. They’re experiencing the effects of warming now. They’re just more difficult to detect here because we are in our winter season.”

It can be especially hard to make this clear when you’re writing about the weather — will it snow today? — instead of climate: — Are we all going to die because of killer storms and failing crops?

Take all the seasonal forecasts released around Thanksgiving, for example. They said this: If it’s cold, it will snow. If it’s warm, it will rain.

Well, duh.

Increasingly, though, it’s climate change that determines that pretty basic weather equation in the mid-Atlantic.

Next week, the forecast calls for days about 10 degrees above the historical norm this time of year. That might be connected to polar ice caps and glaciers melting, reducing their chilling effect. It might not.

But when the Southern Hemisphere experiences extreme heat — the journal Nature predicted the global South will suffer the same record heat we got in 2023 — it can make our winter suddenly much colder.

“You may recall when we have a really, really big cold spell, the meteorologists start talking about the polar vortex,” Myers said. “The polar vortexes are winds around the poles that keep the coldest of the cold around the poles.”

When the heat down South gets really bad, it can reach into the upper atmosphere in what’s called Rossby waves, setting off a chain reaction of energy that leads to a breakdown of the polar vortex — opening the door for plunging temperatures in Maryland.

“What generally caused the polar vortex tipping in 2014-2015 was super-hot air in Indonesia,” Myers said.

Just as an Atlantic hurricane is a creature of energy spawned by heating waters, a deep freeze can be given birth by heating air on the other side of the planet.

“It tips that polar vortex off its rocker,” Myers said.

So, if it gets really cold here as the South swelters — snow instead of rain — yeah, that’s climate change.

“The last significant icebreaking year was in 2018, the last time we cleared the Annapolis Harbor,” Gregg Bortz, a spokesperson for the Department of Natural Resources, wrote in an email. “And before that 2015. In each of those years, the freezing was caused by a polar vortex.”

Icing on the Chesapeake Bay isn’t unheard of, even if the last recorded full freeze was in the winter of 1977. Maryland uses a small fleet of buoy tenders, the vessels named J.C. Widener, Eddie Somers and A.V. Sandusky, plus the utility boat H.J. Elser as icebreakers when needed.

“These boats are prepared every year to respond to icebreaking as needed, especially since for some of our ports (most significantly Smith Island) our boats are a literal lifeline allowing food and fuel to get through when the harbor is inaccessible,” Bortz wrote.

If climate change could bring a deep freeze in January, it also is the reason you might eat different kinds of tomatoes next summer.

In November, the U.S. Department of Agriculture updated the hardiness zones to reflect warmer winters within 5 to 7 miles of the Chesapeake Bay. The zones are a guide on what to plant and when.

“We are no longer a Zone 7B in this area, but a Zone 8 due to the contiguous USA being 2.5 degrees warmer than 11 years ago,” my neighbor Tim said. “For casual suburban gardeners, it’s not a huge deal, but for farmers, it is.”

Winter is when farmers and gardeners start leafing through seed catalogs, looking for crops that can go in the ground earlier than ever and that will tolerate warmer days with fewer clouds.

Farmers are affected by climate change in another way, too. Wild swings between deep cold and warmer-than-normal temperatures confuse plants into blooming at the wrong time.

“It’s always been common, but it does seem like we get longer warm spells,” said Dave Myers, a longtime farmer who now advises farmers for the Maryland Cooperative Extension Agency. “For fruit growers and perennial crops, that’s pretty troublesome. It tends to lead to early bud break.”

Farmers, however, tend to pay more attention to weather than climate.

“It’s all intertwined,” said Myers, no relation to the bay scientist. “I don’t think farmers are too pessimistic about the climate, they’re pretty resilient. They’re looking at next year. Is next year going to be a good year.”

They are paying attention at the Smithsonian Environmental Research Center in Edgewater, where researchers have been studying the warming globe for 37 years — the longest-running climate research project in the world.

They’ve already documented some of the impact.

“One experiment actually simulates a warmer world in this tidal salt marsh,” said J. Patrick Megonigal, senior scientist and associate director of research at the center. “And there, we’re warming the marsh at three different temperatures above ambient that represent different futures.”

Plants stay greener longer into the fall in a warmer future and emerge from the soil earlier in the spring. A dusting of snow vanishes immediately instead of lingering as a sure sign of early winter.

“It’s very visual,” Megonigal said.

What no one can see is the primary focus of the experiments, a kind of doom loop involving microorganisms in the system. Those that make methane gas are much more active in a warmer world, emitting it at faster and faster rates. They add to the greenhouse gases already driving climate change.

“What this means is one greenhouse gas, carbon dioxide, is causing other greenhouse gases to be emitted faster and for its concentrations to go up faster. It’s not a positive feedback,” Megonigal said. “That’s a really dramatic result.”

There are other signs if you look hard — some bad, but not all.

Tundra swan and snow geese that fly south to winter in the Chesapeake might settle down in the marshes of New Jersey instead.

Less snow and ice means less salt spread on the roads and washing into the Chesapeake.

The shad run, the migration of a once plentiful fish on the bay, is changing enough that soon it will no longer happen when the shadbush blooms along the shore.

That old question of rain vs. snow now has to include this: Warm air holds more water — it doubles for every 20 degrees Fahrenheit increase — so when it does rain in winter, it will pour.

And rising waters driven by climate change could one day change the science of studying it on the Smithsonian’s marshes just outside Annapolis.

“The marsh only keeps itself a marsh instead of open water by gaining elevation at the same rate that the sea rises. And if it starts to sink for some reason, that causes the marsh to unravel,” Megonigal said.

Rick Hutzell

rick.hutzell@thebaltimorebanner.com

Rick Hutzell is the Annapolis columnist for The Baltimore Banner. He writes about what's happening today, how we got here and where we're going next. The former editor of Capital Gazette, he led the newspaper to a Pulitzer Prize for coverage of the 2018 mass shooting in its newsroom.

More from Rick Hutzell

It’s never too late to write your mom for Mother’s Day, even when it is.

May 07, 2024

Accept no substitutions or fakes. I’m the real Rick Hutzell.

May 05, 2024

More From The Banner

Sheila Dixon, a ‘filthy’ street and residents who want politicians to put up or shut up

The Climb: Mount St. Joseph’s seniors embark on century-old rite of passage

Missing in Baltimore City: Facebook group helps families search for lost loved ones

Unaccompanied migrant children come to Maryland at a higher rate than any other state