Ozone depletion widely reported in the press. The especially rapid ozone depletion in Antarctica had previously been dismissed as a measurement error. Scientific consensus was established after regulation. While the Antarctic ozone hole has a relatively small effect on global ozone, the hole has generated a great deal of public interest because: Since the ozone layer absorbs UVB ultraviolet light from the sun, ozone layer depletion increases surface UVB levels (all else equal), which could lead to damage, including increase in skin cancer. This was the reason for the Montreal Protocol. Although decreases in stratospheric ozone are well-tied to CFCs and to
Sodium layer typical thickness of 5 km this corresponds to volume density of roughly 8000 sodium atoms/cm. Atoms of sodium in this layer can become excited due to sunlight, solar wind, or other causes. Once excited, these atoms radiate very efficiently around 589 nm, which is in the yellow portion of the spectrum. These radiation bands are known as the "sodium D lines". The resulting radiation is one of the sources of air glow. Astronomers have found the sodium layer to be useful for creating an artificial laser guide star in the upper atmosphere. The star is used by adaptive optics to