The European Space Agency has revealed that the ozone layer hole over Antarctica is the smallest it has been in 10 years and satellites show that the Earth's ozone has been strengthening. Compared to the North Pole, Antarctica has high wind speeds that create a vortex of cold air. Under this extremely low temperature, chlorofluorocarbons - CFCs - deplete the ozone more than it would in higher temperature climates. International agreements, like the Montreal Protocol, were implemented and helped to stop increased CFC damage. This effort proved effective in protecting this vital layer and the hole appears smaller since the mid-1990s.
The northern hemisphere's mountains and hills and valleys prevent a buildup of wind in the Arctic, causing that area to not be as prone to ozone depletion.
Throughout the southern hemisphere, there is a higher risk of cancer, as the ultraviolet radiation is very strong due to ozone depletion. The elements of the Earth's atmosphere and the dynamics of wind and temperature all have an effect on the evolution of the planet's ozone layer. When there is abnormal behavior in the conditions of weather and atmospheric chemicals, extreme ozone conditions can result.
"It happened to be a bit warmer... in the atmosphere above Antarctica, and that meant we didn't see quite as much ozone depletion as we saw [in 2011], when it was colder," said Jim Butler with National Oceanic and Atmospheric Administration's (NOAA) Earth System Research Laboratory in Boulder, Colo.
Scientists collect data from satellite observations and simulations based on atmosphere models. Many instruments have been used over many decades to observe the ozone and combining all of the data can trigger many hypotheses. It's a difficult task, due to the abundance of data available for analysis but with the implementation of the ESA's Climate Change Initiative, a better assessment may be possible.
Ozone layer data records document the variability at multiple scales in space and time. This information is more in depth for scientists to better estimate when the closure of the ozone hole will occur as well as when it began to occur.