After they were over hunted, much like everything in the area in the 1800 to 1900s their numbers have rebounded due to more strict rules around hunting and the fur trade. That doesn't mean their habit is not under serious threat.

Their habit is not under serious threat, simply because it isn't. Polar bears who are used to living in temperatures between -30C and 20C or so, will not mind neither 1.5C increase in average temperature nor even twice or four times that.

What would make anyone believe that they would?

They depend on ice and there’s going to be a whole lot less of it at the North Pole, entirely possible that there will be an ice free North Pole in the next two or three decades, habitat =gone.

Global average temperatures aren’t the whole story.

>in contrast, the GWPF see bear populations doing well to date.

So that's where they get their numbers. And who's GWPF? https://en.wikipedia.org/wiki/Global_Warming_Policy_Foundati... Ah, yes!

The other group the article references, the Polar Bear Specialist Group, sadly isn't much better than the GWPF.

Look at their most recent report, they show "Data deficient" for most subpopulations. I think the other comment is likely correct, the population is going up, but for reasons unrelated to the existence of global warming. https://www.iucn-pbsg.org/

This doesn't fit the environmentalist narrative well, so the most prominent statistics on their homepage aren't directly related to polar bear populations, but things like "The mean rate of decline in summer sea ice area across all subpopulations "

>Of the 19 polar bear subpopulations recognized in 2017, one was in decline, two were increasing, seven were stable, and nine had insufficient data.[48]

https://web.archive.org/web/20151224224314/http://pbsg.npola...

It seems a multispectral satellite photo would quite easily spot bears. Heat signature visible in the IR, and shadow in the visible spectrum.

You could get pretty good population estimates by just reviewing random 1 km^2 samples for bears and then extrapolating.