Sometimes climate change is measured in numbers — degrees warmed, greenhouse gases in the atmosphere, extreme highs, acres burned.
Sometimes it’s measured in memories — of long-ago December mornings, when the temperature often dipped down to zero or of regular pickup hockey games on cranberry bogs that used to reliably freeze.
However it is measured, these days — in a world that has warmed 1.1°C over preindustrial times, thanks to the burning of fossil fuels — the symptoms of our warmed and warming planet became impossible to ignore in the last year, as extreme events ramped up in frequency and severity across the globe.
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2021 was, for many people, the year in which climate change jumped from the part of our brains reserved for future-think — for worries not yet realized — and landed squarely in the now. It was the year that extreme heat rolled into wildfires into poor air quality into endless downpours and flash floods. No more future tense. 2021 was the year that climate change entered the present.
“Our climate is fundamentally altered from what older generations would recall,” said Michael Rawlins, associate director of the Climate System Research Center at the University of Massachusetts Amherst.
In a year when Boston set several record high temperatures, not a single low temperature record fell. Instead, the city experienced nine days in which the coldest point of the day was the warmest it has ever been on that day of the year, going back to the start of the historical record in 1872, according to data from the Northeast Regional Climate Center.
And at this time of year, those warmer temperatures make it that much less likely that, if snow falls, it will stick. Just like in the Arctic, where sea ice reflects the sun’s heat back into the atmosphere, snow cover in New England helps cool the air in winter. But less snow in New England — like less ice in the Arctic — leads to a positive feedback loop, Rawlins explained, where warming begets more warming, and so on.
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Even for climate experts around the state who have long studied and chronicled the rapid changes brought by the warming climate, this year stood out.
“I think the word ‘unprecedented’ got a real workout this year,” said Jennifer Francis, a senior scientist and acting deputy director at the Woodwell Climate Research Center. Francis studies how rapid changes in the Arctic are affecting the jet stream, sometimes depositing frigid Arctic temperatures in lower latitudes, and resulting in weather patterns that can sit in one place for days at a time. That phenomenon, which scientists are racing to fully understand, appeared to be on full display this year.
For 18 days in February, for instance, temperatures in Texas dropped into the low 20s, leading to a major systemic catastrophe as the electrical grid failed to keep up with demand. According to the state, 210 people died, but an analysis by Buzzfeed found that number to be much higher: some 700 people, killed by a weather system that seemed to come out of nowhere.
It turned out to be just the beginning of a year of extreme weather that would hopscotch around the globe, taking thousands of lives and costing billions in damage and response. According to Steve Bowen, head of catastrophe insight on the impact forecasting team at insurer Aon, 2021 is expected to be the sixth time extreme weather catastrophes have cost more than $100 billion — all of which have happened in the last decade.
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The spring saw two weeks of flooding in Australia that displaced 18,000 people, followed by a devastating cold wave in France and cyclones in India, Sri Lanka, and Bangladesh that killed more than 200 people.
Summer ushered in more calamity, with floods in Europe, China, Japan, and the Philippines that killed more than 500 people and Hurricane Ida — the fifth strongest hurricane to make landfall in the United States — that displaced 14,000 people across the eastern US.
In August, scientists from the Intergovernmental Panel on Climate Change issued a report on the widespread, rapid, and intensifying changes taking place on the planet, but in some ways it felt like a footnote, offering scientific proof of the story already playing out across the globe.
In New England, the warmed climate showed itself in both obvious and subtle ways. The June heat wave — the longest in nearly a century—and the wettest July in Massachusetts history were hard to miss. But most residents likely missed what was happening in the ocean.
In June, while out on a normal scientific research cruise, ocean scientist Glen Gawarkiewicz noticed something strange: Where there normally would be fishing vessels, he saw none. Talking with the fishing community, he heard the boats were following bluefin and yellowfin tuna, which were showing up in abundance in areas they normally do not.
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Recently, while examining data from the National Science Foundation Ocean Observatory Initiative, he understood why. Rings of warm water were being pushed off course from the Gulf Stream and encroaching on the continental shelf, bringing with them higher salinity and different fish species.
“I’ve seen that front go inshore for maybe a week to three weeks before, but this was over the entire summer,” said Gawarkiewicz, a senior scientist at the Woods Hole Oceanographic Institution who studies coastal oceanography and changes to the Gulf Stream.
In a year of headline-grabbing climate extremes, Gawarkiewicz said, this was the moment that caught him off guard. It has implications for two different groups he consults with: the Navy, whose submarines could be affected as sound propagates differently in saltier water, and commercial fisheries.
“The thing I see is that these extreme events are getting more extreme in terms of duration and spatial extent,” he said. And the ocean — which requires an enormous amount of energy to heat up, and will take longer than the atmosphere to cool down — is telling a clear story of how climate change is shifting the core ingredients of our once-healthy planet.
“It was just a profound change,” he said, “and one that I certainly would not have anticipated.”
Sabrina Shankman can be reached at sabrina.shankman@globe.com. Follow her on Twitter @shankman.