You may recognize climber Alex Honnold from the Oscar-winning documentary “Free Solo,” when he became the first person to scale Yosemite National Park’s El Capitan without safety gear. Now, in the new National Geographic series “Arctic Ascent,” Honnold sets his sights even higher, on a 4,000-foot sea cliff in Greenland. This time he’s got ropes, but he also has the climate crisis on his mind as he’s joined by a team of scientists led by glaciologist Heïdi Sevestre. Honnold and Sevestre talked with Hari Sreenivasan about what they discovered.

Watch the full Arctic Ascent with Alex Honnold Series on the National Geographic Channel or Disney+.