Ozone depletion on the surface of the cloud crystals is far different from when it occurs in atmosphere. These conditions have led to ozone hole formation in Antarctica. This hypothesis was decisively confirmed, first by laboratory measurements and subsequently by direct measurements, from the ground and from high-altitude airplanes, of very high concentrations of chlorine monoxide (ClO) in the Antarctic stratosphere. Alternative hypotheses, which had attributed the ozone hole to variations in solar UV radiation or to changes in atmospheric circulation patterns, were also tested and shown to be untenable. Meanwhile, analysis of ozone measurements from the worldwide network of ground-based Dobson
Day of the Animals claiming that chemical waste released into the atmosphere has dangerously depleted the ozone layer, which protects all life from the sun's radiation. On the mountain, the hikers stumble upon a camp where a fire is burning and coffee cups are ready to be filled, but nobody is around. Steve says the campers will soon be back. He leads the hikers to a nearby spot to bed down for the night. They build a fire, and while Daniel pulls Steve aside to tell him that something strange is going on in the woods. Steve asks him not to say anything to