Climate change researchers can explain your weather

If you live on Earth, you’ve probably seen some weird or even dangerous weather in the past few years. Maybe it was the hottest and longest heat wave you’d ever been through. Or there was a scary amount of rain from a storm. Or a strong hurricane that seemed to show up out of nowhere.

Changes in the climate are a part of that story. As the Earth warms up, there will be more extreme weather. But such broad statements can make you feel unimportant when what you really want to know is whether or not climate change has affected you.

“You have an extreme weather disaster, and people want to know, ‘Did climate change flood my house?’ Michael Wehner, a senior scientist at Lawrence Berkeley National Laboratory who studies how climate change affects extreme weather, says, “Did climate change make it so hot that my power went out?” “Those are interesting questions.”

Now, scientists can give more and more sure answers to these questions. For some kinds of weather, it’s now possible to say exactly how much worse it was because of climate change. Or that the disaster would not have happened at all if global warming hadn’t happened.

Every heat wave gets worse because of climate change.

Heat waves are the clearest sign that the world is getting warmer. Wehner says, “It seems clear that as the world’s climate warms, heat waves will also get hotter.”

But just how much warmer?

Scientists have figured out how much. “Climate change has raised the temperature of typical heat waves in the U.S. by 3 to 5 degrees Fahrenheit, such as the hottest day of the year or the hottest day every 10 years,” says Wehner.

When heat records keep going down, you can see those extra degrees at work. During a heat wave in June, millions of people in more than a dozen cities in the Western U.S. and Texas felt temperatures that broke records. Most summers, cities like Phoenix, Las Vegas, and Houston set new high temperature records.

But scientists can go even further by using supercomputers and advanced statistics to study the worst heat waves, like the one that killed hundreds of people in Canada and the Pacific Northwest in 2021. In some parts of Canada, it got as hot as 120 degrees, and in Oregon and Washington, it reached 115 degrees.

Scientists were shocked by what they found when they looked at how climate change affected that heat wave. Wehner says, “It would have been almost impossible without climate change.”

How else could you say that? Extreme heat last summer was caused by changes in the climate.

Most scientists talk to each other using numbers. There are pros and cons to that.

Scientists who study climate rarely use the word “cause.” Instead, they use numbers that show exactly how likely an extreme weather event was in the past, before people burned a lot of fossil fuels.

But many scientists know that these numbers might not mean much to the general public.

“In today’s climate, we could say [the heat wave in the Pacific Northwest in 2021] happened once every 1,000 years. Luke Harrington, a senior research fellow at Victoria University of Wellington in New Zealand who studies climate change and extreme weather, says, “It’s about 150 times more likely today than it was in a preindustrial climate.” “But that probably won’t help you understand that [the heat wave] was pretty much never going to happen in a world before factories.”

Wehner says that for more common types of dangerous weather, more detailed numbers can be helpful because they tell people how often they’ll have to deal with certain events.

For example, let’s say a storm brings a lot more rain than usual and causes your house to flood. In the past, a storm like this would have happened only once in a lifetime.

Scientists might look into that storm and find that climate change made it 10 times more likely to happen.

Wehner says, “If that event is 10 times more likely, it will happen every 7 years instead of once in a lifetime.” In other words, weather that used to be very rare happens all the time now. People can make plans for the future if they know this.

In the future, regular weather forecasts may include information about climate change.

In the grand scheme of things, the kinds of research that make this possible are very new. Science moves slowly, on average. But the science of finding climate fingerprints in individual weather disasters has grown up in less than 20 years, in part because so many people want to know how global warming is changing our lives.

Wehner says, “The public has made it clear that they want this.” He says that research methods have become so good that people with less schooling could do the work. “Like predicting the weather, you could hire someone to do this,” he says.

The European Union’s satellite weather service is testing out this kind of service, which would look at how much climate change affected different weather events in Europe.

That would give climate scientists more time to work on the most important questions about extreme weather and global warming.

Scientists have a harder time studying some kinds of weather than others.

Even though scientists understand how climate change affects the weather as a whole, some types of weather are so complicated that it is still hard to say for sure how climate change affects specific events.

For example, as the Earth gets hotter, there are more and bigger wildfires. Plants and soil dry out because of global warming, which also makes it more likely that it will be hot and dry.

Scientists can’t say for sure how much worse or more likely a certain wildfire was because of global warming, though.

Part of the reason is that people have so much control over where fires start and how big they get. Most wildfires are started by people, like when a campfire, a power line, or even a stray cigarette goes out of control. How people take care of the land determines how much trees, bushes, and grass are available to feed the fire. And the firefighters can change how big the fire gets and where it burns.

Megan Kirchmeier-Young, a research scientist at Environment and Climate Change Canada who studies extreme weather, says, “There are so many things going on in any fire, and only some of them are closely related to the climate.”

It is also hard to say that a single hurricane is caused by climate change. Hurricanes are hard to predict and don’t happen as often as other kinds of extreme weather, since only a small percentage of storms that form actually hit land.

It is hard to compare the effects of storms that happened before humans caused global warming to storms that happen now because of global warming.

Still, scientists are often able to measure how climate change affects the rain that comes from hurricanes. Scientists found that climate change made it rain up to 15% more during Hurricane Harvey in 2017. Another study looked at the whole hurricane season of 2020 and found that climate change made it 10 percent more likely that it would rain a lot.

But scientists are still trying to figure out how other changes in hurricanes are caused by climate change, says Jill Trepanier of Louisiana State University, who studies climate change and tropical cyclones.

Hurricanes, for example, are getting stronger, and storms are more likely to get worse quickly. Warmer ocean water is usually to blame for both of these things, but scientists don’t know enough about what’s going on to say that climate change made a certain storm “x” times stronger or “y” times stronger “y” times faster.

“We can’t say, ‘This is why they get worse so quickly.’ She says, “We haven’t solved that problem yet.” “We’re still trying to figure that out.”