That was a quote from Alexandria Ocasio-Cortez.

And the article contains something similar:

“One of my friends was convinced there would be a collapse of society in 2030 and ‘near term human extinction’ in 2050,” said Jeffrey. “She concluded that we’ve got ten years left to live.”

It is in the article.

No, it very much isn't. "Adults tell children the end of the world is coming" and someone's random unnamed teen friend concludes they have ten years left to live are.

Which is significant of nothing at all - mere hyperbole. The only claims based on 12 years I have heard are based on reality of the IPCC reports and their assorted scenarios to track particular temperature changes by 2100. On that there have been claims we have 12 years to get on track - very different to the world ending in 2031. On a Tuesday at 14;00.

> On that there have been claims we have 12 years to get on track

In order to meet an arbitrary mark chosen primarily because people like round numbers. Nonetheless, the IPCC report was reasonable, and didn't conclude with "we're all going to die".

But then celebrities and social media oversimplified that and people who get most of their information from celebrities or social media came to believe that they're going to die, soon.

That's alarmism.

And the author called out alarmism, not the IPCC, so pointing out that the IPCC aren't alarmists isn't relevant.

Multiple claims from XR and "He told me that the Guardian reporter had misunderstood him and that he had said, “It’s difficult to see how we could accommodate eight billion people or even half of that,” not “a billion people.”".

So XR + The Guardian. So it is very much in the article.