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Climate change is making the weather worse: NPR

Katherine Morgan wipes sweat from her brow as she walks to work during a record-breaking heat wave in Portland in 2021. Scientists say the heat wave would have been virtually impossible without human-caused climate change.

Nathan Howard/AP

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Nathan Howard/AP

Climate change is making the weather worse: NPR

Katherine Morgan wipes sweat from her brow as she walks to work during a record-breaking heat wave in Portland in 2021. Scientists say the heat wave would have been virtually impossible without human-caused climate change.

Nathan Howard/AP

If you live on Earth, chances are you’ve experienced some weird or downright dangerous weather in the past few years. It was perhaps a hotter and longer heat wave than ever. Or a thunderstorm that dropped a frightening amount of rain. Or a mighty hurricane that seemed to materialize overnight.

Climate change is part of this story. Extreme weather conditions are more likely as the Earth warms. But such sweeping statements may seem impersonal, when what you really want to know is: has climate change affected me?

“You have an extreme climate disaster, and people want to know: Has climate change flooded my house? Has climate change gotten so hot my electricity went out?” says Michael Wehner, a senior scientist at Lawrence Berkeley National Laboratory who studies how climate change influences extreme weather. “Those are good questions.”

Now, scientists can answer these questions with increasing certainty. For certain types of weather, it became possible to tell exactly how much worse it was due to climate change. Or that without global warming, the disaster would not have happened at all.

Climate change is making every heatwave worse

Heat waves have the clearest link to global warming. “It seems obvious that as the global climate warms, so do heat waves,” Wehner says.

But how much hotter, exactly?

Scientists have quantified this. “For garden-variety heat waves — like the hottest day of the year, or the hottest day every 10 years — in the United States, climate change has increased the temperature of that heat wave. 3 to 5 degrees Fahrenheit,” says Wehner.

You can see those extra degrees in action as heat records fall again and again. Millions of people living in more than a dozen cities in the western United States and Texas experienced record high temperatures during a heat wave in June. Many cities, like Phoenix, Las Vegas and Houston, set new heat records almost every summer.

But scientists can go even further, using supercomputers and advanced statistics to analyze the most extreme heat waves, like the one that killed hundreds in Canada and the Pacific Northwest in 2021. temperatures reached 120 degrees in parts of Canada and reached 115 degrees. in Oregon and Washington.

When scientists analyzed the impact of climate change on this heat wave, they discovered something surprising. “It was practically impossible without climate change,” says Wehner.

Another way to say that? Climate change caused last summer’s extreme heat wave.

Most scientists communicate with statistics. Who has advantages and disadvantages

Climatologists tend to steer clear of the word “cause”. Instead, they opt for numbers that exactly explain the likelihood of an extreme weather event, relative to a world before humans started burning large amounts of fossil fuels.

But many scientists are aware that, to the public, these numbers may not mean much.

“We could say [the 2021 Pacific Northwest heat wave] was a 1 in 1000 year event in today’s climate. Or that it was about 150 times more likely today than in a pre-industrial climate,” says Luke Harrington, a senior researcher at Victoria University of Wellington in New Zealand who studies climate change and extreme weather. “But that’s probably not helpful. [if you want] understand that [the heat wave] wasn’t going to happen in a pre-industrial world.”

Wehner points out that, for the most common types of hazardous weather, more detailed numbers can be useful because they tell people how often they will have to deal with certain events.

For example, imagine there is a thunderstorm that drops a lot more rain than usual and floods your home. In the past, such a storm would have been very rare – a once in a lifetime event.

Scientists could study this storm and find that it was 10 times more likely to occur due to climate change.

“If this event is 10 times more likely, that means it will happen once every 7 years,” instead of once in a lifetime, Wehner explains. In other words, time that was once very rare now happens regularly. And knowing this can help people plan for their future.

In the future, climate change information could be part of regular weather forecasts

The research methods that make this possible are very new, in the scheme of things. In general, science evolves slowly. But the science of finding climate footprints in individual weather disasters has gone from infancy to maturity in less than 20 years, in part because of the huge demand for information about how global warming is changing our lives.

“There’s a clear demand for this from the public,” says Wehner. He says research techniques have advanced to the point that people with less academic training could do the job. “Just like weather forecasting, you can hire professionals to do it,” he explains.

The European Union’s satellite weather service is piloting such a service, which would analyze how much climate change has contributed to individual weather events in Europe.

This would free up time for climate scientists to focus on the most pressing remaining questions about extreme weather and global warming.

Some types of weather are more difficult for scientists to study

Some types of weather are so complex that it is still difficult for scientists to determine the influence of climate change on individual events, even though the global link to climate change is well understood.

For example, wildfires are becoming more widespread and intense as the Earth warms. Global warming dries out plants and soil and makes hot, dry weather more likely.

But scientists aren’t able to say exactly how much worse or more likely a specific wildfire was because of global warming.

That’s partly because humans can play such an active role in starting fires and how big they get. Most forest fires are started by humans – for example, by a campfire, a power line or even a rogue cigarette. Human land management dictates the amount of vegetation such as trees, shrubs or grass available to fuel the fire. And firefighters influence the size of the fire and where it burns.

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

It is also difficult to attribute individual hurricanes to climate change. Hurricanes are both complex and relatively rare compared to other types of extreme weather, especially since only a small fraction of the storms that form actually make landfall.

This small dataset makes it difficult to compare the effects of storms occurring today, with global warming, to storms that occurred before humans caused global warming.

Yet, in many cases, scientists are able to quantify the effect of climate change on hurricane rainfall. Researchers found that climate change caused up to 15% more rain during Hurricane Harvey in 2017. Another study looked at the entire 2020 hurricane season and found that climate change had increased extreme precipitation by 10% for the entire season.

But researchers are still trying to figure out how climate change causes other changes in hurricanes, says Jill Trepanier, who studies climate change and tropical cyclones at Louisiana State University.

For example, hurricanes become more powerful and storms are more likely to intensify rapidly. Warmer seawater is usually to blame for both, but scientists don’t understand what’s going on well enough to say that a specific storm was “x” stronger, or intensified “y.” “percent, faster because of climate change.

“We can’t say ‘That’s why they’re escalating so fast.’ We haven’t solved that problem,” she said. “It’s something we’re still working on.”


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