How scientists are so confident they know what’s causing this insane weather – .

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How scientists are so confident they know what’s causing this insane weather – .


reAle Durran has just suffered a historic heat wave in Seattle, and perhaps more than most locals, he has good reason to be convinced that climate change has something to do with the regional madness that has unfolded. proved particularly extreme next door in Oregon, where dozens of people died.
The University of Washington atmospheric science professor told the Daily Beast that last week’s monstrous stretch – which peaked at 108 degrees on Monday – was “so out of the range of previous heat waves in Seattle that it really extends the credibility of anyone suggesting it’s just natural variability.

Durran isn’t someone who blames climate change every time he sweats. But he’s pondering that question: to accurately attribute seemingly insane weather events, like an entire village on fire in Canada last week, to a warming planet.

Last year, in his jargon-heavy article “Can the Issuance of Hazardous-Weather Warnings Inform the Attribution of Extreme Events to Climate Change? Durran took a close look at what is called the “probability of detection” and the “false alarm report.”

“The purpose of this article,” he explained, “is that to require scientific certainty in the face of an event such as our recent record-breaking heat wave in the Pacific Northwest before accepting the need to take action to stem global warming is as ludicrous as requiring 100% certainty before issuing a tornado forecast. “

He’s not the only one who thinks the skeptics have run out of room – that events have gone beyond reasonable skepticism.

According to legendary Princeton geoscientist Michael Oppenheimer, scientists are no longer guessing when it comes to linking extreme events like this to climate change because now there is a whole new field that aims to tie a beautiful arc around these. same questions.

“There is now a well-developed science of ‘event attribution’ that deals with uncertainty,” Oppenheimer told The Daily Beast. (His own research over the years has focused on the specific dangers of climate change, not necessarily the attribution of events.)

Here is Oppenheimer’s explanation of how event attribution scientists do their job: They use fractional risk attribution (FAR), which he says is “the fraction of the intensity of risk. ‘an event (such as a heat wave) that can be attributed to human-made greenhouse gases. . For example, event attribution scientists calculated the FAR for Hurricane Harvey in 2017 – after the fact – and it had, Oppenheimer explained, about twice what would have been the case without the greenhouse gases. greenhouse at 2017 levels. This gave Harvey an FAR score of 0.5.

Do you have it all?

It doesn’t really matter at the moment, because, according to Emily Williams, an event attribution specialist, currently still a doctoral student. geography student at UC Santa Barbara – there is no FAR score for what just happened to the west coast. “Until a formal attribution study is done on this current heat wave,” told The Daily Beast Williams, who co-authored his university’s fact sheet on heat waves and the climate change, “we won’t be able to say precisely how likely climate change has done it.

However, said Williams, it is nonetheless a “pretty safe bet to venture out and say that climate change has probably at least exacerbated” the situation.

This is because what scientists call the overall “probability distribution” of heat waves has now changed. So even if they haven’t looked back at this latest event (or series of events) and linked it to climate change, enough scientific data has been done to safely say the opposite: they have more. or less predicted that this heat wave would occur. What these former scientists have already demonstrated, according to Williams, is that we are now twice as likely to experience record high temperatures, that 16 percent of North America is now exposed to extreme heat waves, and that when the heat waves come, “they’re hotter now.”

Matthew Hurteau, a biology researcher at the University of New Mexico, studies the interplay between human behavior and the climate system, with an emphasis on fires, such as the one that just burned down an entire Canadian city that had just burnt down. ‘set a national heat record of 121 degrees. . Hurteau conducts his research by looking at reality, and a model of an unchanged climate.

“When I look at the burning climate change footprint in my own research, it usually involves running simulations with and without climate change,” he told The Daily Beast.

But he doesn’t always need a role model to be certain in his mind that climate change is to blame when he sees a fire. “When the Creek Fire was burning in the Sierra Nevada last fall and I was looking at the energy release data from the satellites and how much of the year it was actively burning,” he said, “it was clear that there was an amplification of climate change from this fire.

Nevertheless, it should be noted that some scientists find this methodology of comparison with an unchanged world unsatisfactory. Not because they think recent extreme events should be considered normal, but simply because we live in the aforementioned altered world, and the other is wrong.

Matthew Igel, a cloud atmospheric scientist at the University of California at Davis, told The Daily Beast that now that we have filled our atmosphere with greenhouse gases, “we will not have. still no awareness of Earth without climate change, no matter how excellent our models are or become.

According to Igel’s explanation, you can think of every attribution study almost like a science fiction story about a place called “Earth 2,” where human-made climate change didn’t happen, perhaps because humans do not exist there. And it is only by creating a model of Earth 2 that one can understand why it is so hot here on Earth 1, aka the only Earth that actually exists. “Our statistical knowledge of truly extreme events in some benchmark climates will always be poor,” Igel said. “And whatever, just because we’ve never seen something before doesn’t mean it was impossible, just that it didn’t happen. “

Igel has by no means dismissed the usefulness of the science of attribution – he is simply hesitant to call it conclusive. “These are the questions that keep me awake at night,” he explained.

But the attribution scientists can offer on the link between climate change and, say, your house burned down in a wildfire, is good enough to be used in court. At least according to Michael Burger, professor of law at Columbia and executive director of the Sabin Center for Climate Change Law, which is developing legal techniques to use in the fight against climate change.

“There is nothing new about courts or policymakers making decisions in the face of calculations of probability and varying degrees of scientific uncertainty. It’s the nature of the beast, ”Burger explained. “As a lawyer, you have to deploy the science to make your case and tailor it to the standard relevant to the particular legal problem you are addressing. “

« There was no precedent even close to [Hurricane Harvey] in local historical archives. I think the same is true of the recent Pacific Northwest event.«

“Attribution Science has improved the accuracy of climate data with respect to delineating atmospheric conditions with and without man-made greenhouse gases,” added Lindene Patton, lawyer at the legal and consulting firm Earth and Water Law. Group.

Regarding expert commentary before a judge, she said, “The cutting edge attribution science is pretty good, as good as the morbidity data or demographics or whatever we use. “

Thus, the evidence, as in courtroom the proof – that climate change is the culprit of this heat wave, is not quite there yet. But that doesn’t mean the case against the defendant, anthropogenic climate change, doesn’t look extremely strong.

“Climate change caused by high levels of greenhouse gases alters all of these events to some extent,” Oppenheimer said, “and I’m waiting to see what the scientists doing these calculations say before I specifically decide how. the character of an event has been affected by the greenhouse effect. accumulation of gas. This is precisely what I am now waiting for when it comes to the recent heat wave in the Pacific Northwest. “

However, added Oppenheimer, “some events are so out of the ordinary that you can say right off the bat that there has most likely been a significant contribution to greenhouse gases.” Hurricane Harvey, he said, was one of those cases where he didn’t have to wait for evidence to be fairly sure. “There was no precedent, even close, in the local historical records. I think the same is true of the recent Pacific Northwest event.

According to Williams, the UC Santa Barbara attribution specialist, events like this are “both a window into the future and a reminder of why it is so important to act now to move to a fair and low-carbon economy ”.

Such a “fair, low-carbon economy” is still a long way off, and those who would sit on the sidelines by blurring scientific conclusions have helped slow its creation. According to Durran, we need to stop letting this happen, even if the science of attribution gets it wrong every now and then.

“Some errors will always occur both when issuing weather warnings and when distinguishing between natural variability and human-induced climate change,” he said. “In no case can we allow the possibility of error to completely cripple our response. “

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