Millions of people are now experiencing the effects of climate change firsthand. Blistering heat waves have smashed temperature records around the globe this summer, scorching crops, knocking out power, fueling wildfires, buckling roads and runways, and killing hundreds in Europe alone.

The dizzyingly quick shift from an abstract threat to an era of tumbling temperature records, megadroughts, and pervasive fires has many people wondering: is climate change unfolding faster than scientists had expected? Are these extreme events more extreme than studies had predicted they would be, given the levels of greenhouse gases now in the atmosphere?

As it happens, those are two distinct questions, with different and nuanced answers.

For the most part, the computer models used to simulate how the planet responds to rising greenhouse gas concentrations in the atmosphere aren’t wildly off the mark, especially considering that they aren’t geared for predicting regional temperature extremes. But the recent pileup of very hot heat waves does have some scientists wondering whether models could be underestimating the frequency and intensity of such events, whether some factors are playing more significant roles than represented in certain models, and what it all may mean for our climate conditions in the coming decades.

Let’s address these issues point by point.

Is climate change largely to blame for these extreme heat waves?

Yes. Global warming has established a hotter baseline for summer temperatures, which dramatically increases the odds of more frequent, more extreme, and longer-lasting heat waves, as study after study after study has clearly shown. 

“Climate change is driving this heat wave, just as it is driving every heat wave now,” said Friederike Otto, co-lead of World Weather Attribution, in a press statement about the unprecedented temperatures across Europe in recent days. “Heat waves that used to be rare are now common; heat waves that used to be impossible are now happening and killing people.”

Is climate change unfolding faster than scientists expected?

The answer, at least in the broad sense, is no. In fact, the linked rise in greenhouse gas levels and global average temperatures has tracked tightly within the spread of model predictions, even dating back to cruder climate simulations from the 1970s.

Several researchers and studies, including the latest UN climate report, have highlighted just how closely observed temperatures have followed predicted increases. The resemblance is uncanny (almost as if the world should have heeded the warnings of climate scientists decades ago).

Tweeted by Zeke Hausfather (@hausfath) on October 23, 2020.

In fact, the current concern among researchers is that the latest generation of models are collectively running too hot, potentially projecting excessive levels of warming from increased carbon dioxide concentrations, as Zeke Hausfather, Kate Marvel, Gavin Schmidt, and other scientists noted earlier this year in Nature.

re climate models wrong about extreme events?

Sometimes, but it’s a complex question.

Certain real-world events have happened faster or to greater degrees than predicted by past or current models, including the loss of Arctic sea ice, the amount of land burned by wildfires, and the rapid increase in extreme temperature events in Europe in recent decades, scientists say.

“When it comes to certain types of extreme events, I think there is some evidence that things are changing faster than had been expected, or are explicitly represented in global climate models,” says Daniel Swain, climate scientist at the University of California, Los Angeles.

“But,” he adds, “maybe that shouldn’t be too surprising.”

That’s because, for the most part, climate models were not designed to predict regional extreme events. Their main task is to simulate average temperature changes across long time periods and wide areas. 

Researchers are well aware of, and have always been clear about, the shortcomings of climate models. While they’re continually improving, they remain rough computer simulations limited by human understanding of the climate system; the complex interactions among earth systems; computational power; and the cost of running the models numerous times to explore the spectrum of possibilities. And they still divide the planet into relatively large blocks to make the computation tractable—cells ranging in size from dozens to hundreds to thousands of square kilometers. This limits what can be predicted about local weather events with high accuracy.

It can also be difficult to tell whether some of the weather events we’re seeing are occurring outside the bounds of model findings. For

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By: James Temple
Title: Do these heatwaves mean climate change is worse than we thought?
Sourced From: www.technologyreview.com/2022/07/21/1056291/do-these-heatwaves-mean-climate-change-is-worse-than-we-thought/
Published Date: Thu, 21 Jul 2022 07:55:00 +0000