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2025 started off with a flurry of intense weather. Southern California experienced bursts of 

 that spread record-breaking destructive wildfires. Major winter storms have dumped snow and cold weather on the Mid-Atlantic and the South. And in the midst of the weather news, scientists from major meteorological associations around the world reported that human-caused climate change drove 

2024 to be the hottest year in human history

In the past, climate scientists often said that individual weather events couldn't be connected to human-caused climate change. But in the last decade, 

 has allowed researchers to pinpoint the impact of climate change on weather disasters like 

Not every weather fluctuation is demonstrably affected by climate change. But the impact of the steady increase in global temperature is now detectable in many extreme weather events—and likely many of the more normal ones, too, says Justin Mankin, a climate scientist at Dartmouth College.

"The trends in climate are shaping new weather possibilities that were maybe unprecedented," Mankin says.

What's the difference between climate and weather, anyway?

Scientists have a saying: climate is what you plan for and weather is what you get.

Climate scientist Danielle Touma of the University of Texas, Austin, explains it this way. "The climate is basically the clothes you have in your closet," but what you pick out to wear every day tells you about the weather. So in Colorado, where Touma used to live, her winter wardrobe was full of jackets and sweaters—ready for the winter 

But sometimes there was a warm day when she would dig a T-shirt from the back of a drawer.

Scientists usually define the climate of a place as the 30-year average of its weather. So weird weather does factor in, but isn't as important to the average as more common conditions, says Deepti Singh, a climate scientist at Washington State University. And scientists expect the variation in day-to-day weather to persist, even as climate change evolves.

Does human-caused climate change affect weather?

 1.3 degrees Celsisus since the mid-1800s

, when people started burning vast amounts of fossil fuels. The pollution from that burning traps heat inside Earth's atmosphere, slowly heating up the air, oceans, and land.

The temperatures' slow creep upward doesn't always noticeably affect daily weather, at least not in obvious ways, Singh says. But planet-scale warming is 

probably affecting weather basically every day

"Everything we're experiencing, it is occurring in a different environment," Singh says. So the weather itself, "to some extent, is being influenced by these changes."

 in many parts of the U.S. and beyond: states like

 experience more than a week fewer freezing days now than they would in a world without climate change. And heat extremes have also increased. The number of heat waves in the U.S. has 

A changing climate also reshapes complicated atmosphere and ocean patterns—sometimes introducing new or extraordinary weather outside of what people have experienced in the past. The deadly 2021 heat wave in the Pacific Northwest, for example, was demonstrably hotter because of climate change—but 

the atmospheric conditions that allowed it to occur

 in the first place were also essentially unprecedented in the region.

"We've kind of put the climate on steroids," says Alex Hall, a climate scientist at the University of California, Los Angeles. "But once in a while there'll be something really extreme that will occur that will be way outside the range of what the atmosphere was capable of before."

 called "detection" and "attribution." They use climate models that represent Earth's physics to simulate how the planet's climate and weather events would behave if humans had not burned vast quantities of fossil fuels. By comparing that hypothetical situation to the one that exists, they can see if human-caused climate change affected the likelihood of weather events happening—and in many cases, how big the influence was.

For example, they could see that Hurricane Helene's deadly rainfall was 

 absent human-caused climate change, and at least 40% more likely.

Mankin compares the technique to clinical trials in medicine. "You want to compare a distribution of medical outcomes in a population that received the drug, the treatment group, to a control group that didn't receive the drug," Mankin says. Only in this case, the drug is fossil fuel burning.

Alejandra Borunda

Author

Sometimes, weather is just weather. And other times human-caused climate change had an obvious impact. 

Weird weather isn't always because of climate change — but sometimes it is

Go Deeper.

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