ozonedepletion

Ozone depletion refers to the long-term thinning of the stratospheric ozone layer, especially over the Antarctic and, to a lesser extent, the Arctic. The ozone layer absorbs most of the sun’s harmful ultraviolet-B radiation, helping to protect living organisms on Earth.

Human-made ozone-depleting substances, such as chlorofluorocarbons (CFCs), halons, carbon tetrachloride, and methyl chloroform, release chlorine and bromine in the stratosphere when exposed to UV light. These elements participate in catalytic cycles that destroy ozone molecules. Many of these substances have long atmospheric lifetimes, so their effects persist for decades after emission.

In the 1980s, measurements revealed a pronounced ozone hole over Antarctica. The Montreal Protocol of 1987, along with later amendments, phased out production of many ozone-depleting substances. Since the late 1990s, observations show signs of recovery in many regions, though the process is slow and regionally variable. Full restoration of the ozone layer depends on continued compliance and the fate of long-lived substances, with projections often placing near-complete recovery around 2060 to 2080, depending on future emissions and climate interactions.

Impacts of ozone depletion include higher levels of ultraviolet-B radiation at the surface, which can increase risks of skin cancer and cataracts in humans, as well as affect ecosystems, marine phytoplankton, and crop yields. Ozone depletion also interacts with climate patterns, influencing regional temperatures and atmospheric circulation.

Monitoring of ozone uses satellites, ground-based spectrometers, and ozonesonde balloons. Ozone is commonly expressed as total column ozone in Dobson units, and regional thinning is observed as an ozone hole, notably over Antarctica during southern spring.

Ongoing study of ozonedepletion considers climate change, which can alter stratospheric temperatures and chemical cycles, potentially affecting recovery timelines.