Maybe it was the unprecedented floods in Europe and China that did it. Perhaps it was the deathly heat dome in the Pacific Northwest, or the massive wildfires stretching across more than a million acres of the West.
Or maybe it was closer to home — the record-hot June; the rain-soaked July; the smoke-tinged skies and eerily orange sun — that made you wonder if this might be more than a random, rotten run of very bad news. Could this be climate change?
To put it bluntly, according to climate scientists: Yes, it is.
“We are absolutely seeing the face of climate change in these extremes,” said Jennifer Francis, a senior scientist at the Woodwell Climate Research Center.
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If you’ve known where to look, the signs have been there for years — in the shrinking sea ice, and the crisis unfolding in low-lying island nations. But what is in full view now, in a way that it hasn’t been before, is that extreme weather events reliably traced to climate change are happening now with more frequency, more severity, and more damage to human life and property. And it’s going to get worse.
Some of the events of this summer have surprised even the climate experts, whose models do a good job of projecting what to expect on a warming planet, but not with the granularity to predict exactly when or where things could go horribly wrong. Which means that as the world continues to warm, these kinds of catastrophes could happen anywhere — including New England.
“Everybody is feeling it one way or another, whether or not the extreme event is in their own backyard,” said Francis. “It’s just everywhere you look.”
As your climate-denying neighbor might remind you, rainy summer days have always happened, and so have heat waves. But what’s happening now is that climate change — and the 2 degrees of warming that the world has already experienced since preindustrial times — is being added on top of those existing weather patterns, making them much more intense.
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“This is evidence of climate change, this is evidence of natural variability, and this is evidence of the fact that the two can line up and give you even larger extremes,” said Peter Huybers, a professor of earth and planetary sciences at Harvard University.
In Massachusetts, Worcester recorded its wettest July on record when there were still 12 days left in the month. A June heat wave was the longest that Boston had experienced in nearly a century — part of a trend of a rising incidence of days that soar above 90 degrees and don’t fall below 70 at night.
Across the world, the signs have been more troubling. Just this week, cellphone videos recorded a horrifying scene in China as passengers were trapped inside subway cars as floodwaters rose, drowning some of them. A year’s worth of rain fell in just three days. It was eerily similar to floods that washed out entire villages in Germany and Belgium just days earlier.
Meanwhile, more than 400,000 acres of land in Oregon have been charred in the Bootleg Fire — one of more than 80 fires currently burning across the West, where an unrelenting heat wave has yet to die down after pushing temperatures above 100 degrees for weeks. That heat is believed to have killed as many as 500 people in British Columbia, as well as 95 people in Oregon and another 20 in Washington. Preliminary data showed that more than 1 billion sea creatures along Vancouver’s coast were also killed by the heat dome — cooked in the soaring temperatures that an international team of scientists said would have been “virtually impossible” without climate change.
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And at the top of the world, a heat wave in Russian Siberia — above the Arctic Circle — brought temperatures up to 118 degrees in late June. Now, hundreds of fires are burning through the subarctic taiga forests there for the second year in a row.
It’s no coincidence that all of these extreme events are happening at roughly the same time. The planet we live on is a connected place, regulated by systems that inform and relate to each other — a delicate balance that, despite the chaos that’s inherent in weather systems, historically made a certain amount of sense.
But as the planet has warmed, that has changed. Nowhere has warmed as much as the Arctic, and as any Arctic researcher will tell you: What happens in the Arctic, doesn’t stay there.
The Arctic is warming three times faster than the rest of the world becauseits icy cover is melting rapidly and exposing the ocean below. Once exposed, instead of reflecting heat back to the atmosphere, the ocean absorbs it, leading to rapid warming.
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Climate scientists are racing to understand how the dramatic changes happening there are impacting the rest of the world.
Francis, of the Woodwell Center, is among the researchers leading the way on that work, as scientists coalesce around an understanding that extreme warming in the Arctic is weakening the jet stream — that fast-moving river of wind high in the atmosphere that creates and steers most of the weather we experience in the Northern Hemisphere.
“Whenever you mess with the wind, you’re going to mess with the weather,” she said.
That’s showing up in a few ways. With weaker winds, there’s less force to move a weather system, which can lead to heavy rains or extreme heat just parking itself in one place for longer than expected periods of time.
As the heat dome was settling in over western Canada and the Pacific Northwest in late June, satellite images showed that the jet stream had taken a strange dip, curving northward and looping up and over that region, meaning there was no powerful, high-altitude wind to move the system along, said Francis.
Likewise with the eastern European rains and resulting floods. In that case, Francis said, an extreme southward dip in the jet stream allowed the rains to sit and sit.
When it comes to rain, there’s another issue at play too, because a warmer atmosphere holds more water. “The atmosphere can hold 4 percent more water for every 1 degree Fahrenheit of warming,” said Michael Rawlins, of the Climate System Research Center at the University of Massachusetts Amherst. When you have a storm system with significantly more water in it just sit over one spot, what might have been a rainy day a few decades ago looks more like a tragedy.
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That’s what happened in Texas in 2017, when Hurricane Harvey sat over Houston and dumped up to 40 inches of rain in three days, killing 80 people. Climate scientists found that climate change made those record rains at least three times more likely to happen. They also found that even under a best-case scenario of global warming, in which the world acts rapidly and decisively to eliminate fossil fuels, similar extreme rainfall could become a further three times more likely to occur by the end of the century.
If no efforts are made, the researchers found, rainfall events on the scale of Hurricane Harvey could be up to 10 times more likely by 2100.
These extremes come with deadly consequences, and no event is more dangerous than extreme heat, which killed more than 11,000 Americans between 1979 and 2018, according to the EPA.
As climate change progresses, that toll is expected to climb, including in Boston. A 2013 study found that heat-related deaths in Boston would see a four-fold increase by the 2080s under a moderate-warming scenario in which emissions decline, but not rapidly. In a scenario in which emissions continue to rise, those heat-related deaths would see a seven-fold increase, according to the study.
The potential outcomes are dire, which makes it all the more important that action to combat climate change comes swiftly, said Francis.
“As awful as these events are, they are helping people to realize that they’re being affected by climate change today,” she said. “This is not a global warming story of the gradual warming of the planet on average. This is the much more personal impact of climate change.”
Sabrina Shankman can be reached at sabrina.shankman@globe.com. Follow her @shankman.