Washington: Satellite images show that the recent ozone hole discovered over Antarctica was the smallest seen in the past decade.
Long-term observations also reveal that Earth`s ozone has been strengthening following international agreements to protect this vital layer of the atmosphere.
According to the ozone sensor on Europe`s MetOp weather satellite, the hole over Antarctica in 2012 was the smallest in the last 10 years.
The instrument continues the long-term monitoring of atmospheric ozone started by its predecessors on the ERS-2 and Envisat satellites.
Since the beginning of the 1980s, an ozone hole has developed over Antarctica during the southern spring - September to November - resulting in a decrease in ozone concentration of up to 70 percent.
Ozone depletion is more extreme in Antarctica than at the North Pole because high wind speeds cause a fast-rotating vortex of cold air, leading to extremely low temperatures.
Under these conditions, human-made chlorofluorocarbons - CFCs - have a stronger effect on the ozone, depleting it and creating the infamous hole.
Over the Arctic, the effect is far less pronounced because the northern hemisphere`s irregular landmasses and mountains normally prevent the build-up of strong circumpolar winds.
Reduced ozone over the southern hemisphere means that people living there are more exposed to cancer-causing ultraviolet radiation.
International agreements on protecting the ozone layer - particularly the Montreal Protocol - have stopped the increase of CFC concentrations, and a drastic fall has been observed since the mid-1990s.
However, the long lifetimes of CFCs in the atmosphere mean it may take until the middle of this century for the stratosphere`s chlorine content to go back to values like those of the 1960s.