I was born in a snowstorm. Family lore goes like this: my dad was away at a conference when my mom went into labor a month early, and she called his best friend to come dig out the car and take her to the hospital. I took two days to come out—unwilling, maybe, to emerge into the frigidity of Boston in January. My father rushed back from Cleveland while my mom fought through contractions. There was an empty lot that she could see from her window at Beth Israel Hospital, and as she waited, she watched someone stomping out messages in the snow. “Hello,” they wrote in boot tracks, which I take as my welcome to earth.
I’ve held to that story, that I was born on a powder day, and as often as I can, I go skiing every January 12. But lately, it’s been feeling like more of a fable. Last winter I scraped through a high and dry day in Big Sky, Montana, skittering over rocks off the top of the tram, and this year I camped in the Crystal parking lot, soggy in the first real storms of the season, which showed up warm and waterlogged. When I called my parents to thank them for having me, they had just come back from kayaking on the South Shore. It had been nearly seventy degrees in Massachusetts.
I go through life assuming some level of stationarity in the weather, and I don’t think I’m alone. We look at forecasts to plan our adventures. We book huts and buy plane tickets, gambling that it will be snowy in the mountains or sunny on the coast. We have personal barometers, based on history. I think it should be snowy in mid-January in New England, because that’s what my life has shown me. But now things are changing so quickly that history can’t predict the future.
A study published in the January issue of the journal Nature Climate Change shows just how much human-caused climate change is altering the weather. I’m not just imagining that it’s not as snowy as it used to be on my birthday—there is tangible, trackable change. “The global information allows us to now detect climate change for any single day since early 2012,” says the study’s lead author, Swiss climate scientist Reto Knutti.
We’ve known for a long time that global temperatures are on the rise, but weather and climate are different things. (“Climate is what you expect, weather is what you get,” the study quips.) But through machine learning, Knutti and his colleagues were able to analyze patterns of temperature and moisture and show that over the recent past, human-generated climate change has altered both factors beyond natural variability. “We show that once you start looking at weather at a larger scale, you start to see the effect of climate change,” Knutti told me by phone, “and once you look at the whole globe, you recognize it immediately, from any single day.”
Knutti says the study was motivated in part by a snide January 2019 tweet from President Trump slamming the concept of climate change in the face of a cold snap. “This led to a lively debate about whether a single day could be informative at all about climate change,” he says. “Could we detect climate change in a single year, a month, a day?”
It turns out they could. Knutti and his colleagues created a model that showed global weather on any given day, compared it to natural variability, and were able to see distinct changes. This is the first time it’s been proven on such a short timescale, and Knutti says part of the innovation of the study is the methodology. The machine-learning models allow us to look at recent history and show how quickly things are changing. Even since the Intergovernmental Panel on Climate Change Fifth Assessment Report in 2014, which synthesized anthropogenic change, impacts have heightened. “Since then we haven’t had a single day of ‘normal’ weather globally,” he says. “Yesterday was climate change, today is climate change, and tomorrow will be as well.”
That’s one of the important things to draw from the study, both selfishly as people who want to make plans to be outside and as humans who are trying to make sense of the myriad ways the world is being altered around us. On the day of my birth, 36 years ago, the high temperature in Boston was 20. This year it was 69. That’s the difference in weather. Those are specific data points, but if you look over time, there’s a significant upward temperature trend. That’s climate, that’s what’s happening globally, not just at a single point. If I track my birthday other places—say, in Seattle, where I live now—I can see wide swings in temperature and precipitation but also a larger warming trend. And that’s where the personal becomes political and where climate has been messing with my birthday joyriding.
Memory can be foggy—we can have trouble remembering the specifics of any given storm or season, but now we have data to prove the curve of climate change in our own personal histories. We can no longer just blame nostalgia if the snowpack feels shallower. “The implication for the public is that we should stop pretending that climate change is some remote, distant threat,” Knutti says. “It’s happening now, every day.” No matter where I am next January, I can expect things to be different than they have been in the past.