Twenty years ago, National Geographic photographer James Balog was a climate change sceptic, until he started photographing the retreat of the world’s glaciers. Together with filmmaker Jeff Orlowski, he treks to remote locations to set up the Extreme Ice Survey. The challenges are immense: installing custom-built time-lapse cameras across three continents, in some of the harshest conditions on earth. What they capture will blow you away; the stunning and terrifying images from Greenland to Iceland, Nepal to Alaska cannot be ignored. If ever there was a call to action, the visual proof of the extinction of these incredible yet vulnerable features of our physical environment is it.