When wildlife photographers and filmmakers Paul Nicklen and Cristina Mittermeier saw a starving polar bear in northern Canada last summer, they shot a video that they hoped would shock the world into paying attention to the threat of climate change.

But neither could have predicted that their heart-wrenching video, released last month, would reach tens of millions of people around the world. Or that so much of the reaction to it would be so nasty.

Social media platforms lit up with support for Nicklen’s and Mittermeier’s work, applauding their effort to put a dramatic face on climate change’s potential toll. But those same platforms exploded with accusations that the two photographers—and National Geographic—overstated what can be known about the link between climate