A version of this article originally appeared on Climate Progress.

Climate change is already keeping climbers off Everest. (Photo by Mandala Travel.)

Mount Everest has become a microcosm for the rest of the planet. Once an isolated place for adventurers, the mountain is now extremely crowded, polluted, and facing dramatic changes as global temperatures rise.

As commercial climbing outfits have blossomed over the last two decades, more and more climbers are flocking to Everest. The overcrowding problem became clear earlier this month when the mountain was clogged by a traffic jam of roughly 150 people trying to reach the summit — contributing to the death of four climbers.