Ozone (O3) is a naturally occurring trace gas in the stratosphere that inhibits harmful UV radiation from reaching Earth’s surface. Ozone in the troposphere is a pollutant, harmful to all living things. Ozone is strongly linked to climate by its influence on Earth’s radiation budget. The amount of ozone in the global stratosphere began to decrease in 1980 due to catalytic reactions with chlorine and bromine from man-made CFCs and other halocarbons. Severe, seasonal depletions over Antarctica (“ozone hole”) have occurred annually since 1985. Thanks to the Montreal Protocol, an international treaty enacted to curtail the production and consumption of ozone-depleting substances, stratospheric ozone levels are expected to return to pre-depletion values.
Carbon Cycle and other GHGs
Dale Hurst, Paolo Laj
Total column Ozone; Tropospheric Ozone; Ozone profile in upper troposphere and lower stratosphere; Ozone profile in upper strato-and mesosphere
Global Ozone Change
Figure: Changes in global total column ozone. Global total ozone measured by satellite instruments decreased by about 5% between 1980 and 1993, relative to the average value for 1964-1980. The steep drop during 1991-1993 is attributed to increased stratospheric aerosols injected by the eruption of Mt. Pinatubo in 1991. The aerosol effects slowly dissipated during the next decade, but global total ozone remained about 4% lower than in 1964-1980.igure: Global total ozone changes. Global total ozone values decreased by an average of a few percent in the last two decades, as measured by satellite instruments. In the top panel, global ozone changes are compared with average global ozone found in the period of 1964 to 1980. Between 1980 and 2006, the largest decreases occurred following the volcanic eruption of Mt. Pinatubo in 1991.