The ozone layer, a region of the Earth's stratosphere that absorbs most of the ultraviolet (UV) radiation from the sun, serves as our planet's natural sunscreen protecting humans, plants and animals from DNA-damaging solar radiation.
In the 1980s, scientists noticed a dramatic thinning of the ozone above Antarctica. The damage was primarily attributed to gases known as chlorofluorocarbons (CFCs), which were then popularly used in air conditioning units, refrigerators and chemical sprays.
In a bid to to protect the ozone layer, nations agreed to phase out the ozone-depleting substances through an international treaty known as the Montreal Protocol.
Now, scientists celebrate the success of this agreement as a new study revealed that the Antarctic ozone layer now shows signs of healing.
In a new study published in the journal Science on June 30, MIT professor of atmospheric chemistry and climate science Susan Solomon and colleagues found evidence that the ozone hole is healing with the Antarctic ozone hole believed to have shrunk by more than 4 million square kilometers (1.5 square miles) and is no longer as deep as it used to be.
The researchers likewise found that more than half of the shrinkage can be traced to the reduction in atmospheric chlorine. Very little chlorine naturally exists in the atmosphere, but using CFCs introduces chlorine into the ozone layer.
Although the improvement has so far been slight, and full recovery is not expected to happen until the middle of the century, experts said it is an indication that the 1987 treaty that aimed to phase out CFC is already seeing its intended effect.
"Industrial chlorofluorocarbons that cause ozone depletion have been phased out under the Montreal Protocol," Solomon and colleagues wrote in their study.
"A chemically driven increase in polar ozone (or "healing") is expected in response to this historic agreement. Observations and model calculations taken together indicate that the onset of healing of Antarctic ozone loss has now emerged in September."
The findings of the study by Solomon and colleagues support the results of a 2009 analysis made by NASA scientists that showed what could happen to the world if there was no international agreement to ban ozone-depleting substances.
Paul Newman, from the NASA's Goddard Space Flight Center, and colleagues simulated "what might have been" if CFCs and similar chemicals were not banned through the Montreal Protocol.
They found that if nothing has been done to stop the damages to the ozone layer, 17 percent of all ozone would be depleted globally by the year 2020. By the year 2065, UV radiation that hits mid-latitude cities like Washington D.C. would be strong enough to cause sunburn in as little as five minutes.
"We simulated a world avoided," said Newman."It's a world we should be glad we avoided."
