Denver's Brown Cloud
What happens with a temperature inversion.
Clean air has long been an important reason people moved to Colorado. By the 1970s, the pollution hanging over the city had a name - the brown cloud. Denver's location at the foot of the Rocky Mountains make it prone to temperature inversions in which warm air traps cooler air near the ground, preventing pollutants from rising into the atmosphere. Learn more about temperature inversions with this eye-catching hands-on science experiment.