Sure, it's in the original article.

> By telling the story of one polar bear, Nicklen hopes to convey a larger message about how a warming climate has deadly consequences.

I don't think the photographer would say that the polar bear should convince anyone that climate change is occurring. Instead, they assume that reasonable people are already convinced, and are trying to demonstrate a reason one should care.

No. "Here's an example of the effects of climate change" is not the same thing as "this is proof of climate change"