The world will likely reach the key warming threshold in 10 to 12 years

The world will likely cross the internationally agreed climate change threshold in about a decade and continue to heat up to cross a next warming limit around mid-century, even with big reductions in pollution, predicts artificial intelligence in a new study that is more pessimistic than the previous one. modeling.

The study published in the journal PNAS on Monday reignites the debate on whether it is still possible to limit global warming to 1.5 degrees Celsius, as required by the 2015 Paris climate agreement , to minimize the most damaging effects of climate change. According to scientists, the world has already warmed by 1.1 or 1.2 degrees since pre-industrial times, the middle of the 19th century.

Two climatologists using machine learning have calculated that the Earth will cross the 1.5 degree mark (2.7 degrees Fahrenheit) between 2033 and 2035. Their results match other more conventional methods of predicting when the Earth will cross the bar, but with a little more precision.

“There will come a time when we will call the 1.5C target for maximum warming dead, beyond a shadow of a doubt,” said the director of Brown University’s environment institute. , Kim Cobb, who was not part of the study, in an email interview. “And this document could be the beginning of the end of the 1.5°C target.”

Noah Diffenbaugh of Stanford University, co-author of the study, said the world was on the verge of the 1.5 degree mark under “any realistic emissions reduction scenario”. Avoiding a 2 degree rise, he said, may depend on nations reaching zero emissions targets by the middle of this century.

The artificial intelligence-based study found that the temperature increase was unlikely to be kept below 2 degrees Celsius, even with severe emissions cuts. And that’s where AI really differs from scientists who had made predictions using computer models based on past observations, Diffenbaugh said.

In a high pollution scenario, the AI ​​calculated that the world would hit the 2 degree mark around 2050. Less pollution could prevent this until 2054, according to machine learning.

In contrast, the United Nations Intergovernmental Panel on Climate Change estimated in its 2021 report that the same pollution reduction scenario would see the world exceed 2 degrees in the 2090s.

Cornell University climatologist Natalie Mahowald, who was not part of Diffenbaugh’s study but was part of the IPCC, said the study made sense, matched what scientists knew, but seemed a bit more pessimistic.

There is a lot of power in using AI and in the future it can be shown to produce better projections, but more evidence is needed before concluding this, Mahowald said.

Normally, climatologists run a bunch of computer model simulations, some running hot and some running cold, and then try to figure out which ones do the best job. This is often based on their performance in the past or in past simulations, Diffenbaugh said. What AI does is now more tied to the climate system, he said.

“We use this very powerful tool that is able to take information and integrate it in ways that no human mind is capable of, for better or for worse,” Diffenbaugh said.

Every year, government climate negotiators at a United Nations summit proclaim that they have succeeded in “keeping 1.5 alive”. But with the latest study, there is a gap between scientists about the truth. Diffenbaugh said there has already been so much warming that no matter how much pollution falls over the next few years, the world will reach 1.5, according to AI figures.

Zeke Hausfather of technology company Stripe and Berkeley Earth, which was not part of the study, agreed, saying it was time to “stop pretending” that limiting warming to 1.5 degrees is possible. Some scenarios see temperatures warming past the mark and then falling again, known as an “overshoot.”

Other scientists not involved in the study, such as Michael Mann of the University of Pennsylvania and Bill Hare and Carl-Friedrich Schleussner of Climate Analytics, maintain that 1.5 is still alive. They say a rapid decarbonization scenario that Diffenbaugh did not examine shows the world can generally stay below the threshold.

If the world can halve its carbon emissions by 2030 “then warming can be limited to 1.5 degrees” with a slight overshoot and then cuts to go below, Hare said.

To believe that the world can no longer keep warming below 1.5″ is a self-fulfilling prophecy,” Mann said. “Ultimately, it’s easy to overinterpret the meaning of a specific threshold like 1.5°C warming. The challenge is to limit warming as much as possible.


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