Group clones California giant trees to combat climate change

At the foot of a giant sequoia in California's Sierra Nevada, two arborists stepped into harnesses then inched up ropes more than 20 stories into the dizzying canopy of a tree that survived thousands of years, enduring drought, wildfire and disease. There, the arborists clipped off tips of young branches to be hand-delivered across the country, cloned in a lab and eventually planted in a forest in some other part of the world.