https://phys.org/news/2018-05-cloudsrevealing-trees-emissions-air.html > "You really feel what it's like to be a leaf in the upper canopy," he said. > The Amazon is the world's largest and most diverse tropical rainforest, stretching over nine countries. While human-made emissions pollute the air in the dry season, the air above the Amazon in the wet season is one of the cleanest places on earth.