Ozone depletion occurs due to chlorine and bromine released from human activities. Global ozone levels decreased by 5% between 1970 and mid-1990s. Largest decreases occur in polar regions, especially Antarctica. UV radiation increases, leading to skin cancer and immune system damage
Iodine has only two stable oxides: iodine tetroxide and iodine pentoxide. Many other oxides exist in trace quantities or are hypothesized
Stratosphere is Earth's second-lowest atmospheric layer. Temperature increases with altitude due to ozone layer absorption. Equatorial stratosphere reaches 20 km, mid-latitude 10 km, poles 7 km. Winds can reach 60 m/s in Southern polar vortex
Ozone layer absorbs 97-99% of Sun's UV radiation in stratosphere. Located between 15-35 kilometers above Earth. Contains less than 10 parts per million ozone compared to atmosphere's average 0.3. Created by UV light splitting oxygen molecules into ozone
Protocol was signed in 1987 to protect ozone layer from depleting substances. First universally ratified UN treaty, with 198 parties (197 states, EU). Scientific research discovery in 1973 led to 18-month negotiations
Ozone levels have decreased by about 4% in Earth's atmosphere since 1970s. Antarctic ozone hole forms during spring, destroying 50% of lower stratospheric ozone. Ozone hole is smallest since 1982, expected to recover by 2075