The expansion of the Antarctic ozone hole to a size larger than the whole continent of North America has been recently recorded by scientists, but climate experts from the United Nations said that the information is no reason for alarm.
Scientists from the U.N.'s World Meteorological Organization said that the large size of the hole was caused by strangely cold temperatures and weak dynamics in the stratosphere.
According to NASA, the ozone layer in Antarctica expanded to 10.9 million square miles on Oct. 2, and has been setting daily records throughout the month. The largest recorded Antarctic ozone hole size was 11.1 million square miles, seen 15 years ago. Last year, the size of the ozone hole was 9.3 million square miles.
"This shows us that the ozone hole problem is still with us and we need to remain vigilant. But there is no reason for undue alarm," said senior scientist Geir Braathen of WMO's Atmospheric and Environment Research Division.
The ozone layer shields the Earth from ultraviolet (UV) radiation coming from the Sun, and it can be depleted by chemicals called ozone-depleting substances which include chlorofluorocarbons and bromofluorocarbons. If the ozone layer is depleted, more dangerous and unabsorbed UV rays are able to reach the surface of the planet, scientists say.
Bryan Johnson, a scientist from the National Oceanic and Atmospheric Administration (NOAA), explained that the agency's instruments measured almost 100 percent ozone depletion in the Antarctic ozone layer which was nine to 12 miles above the surface of the Earth. He said that rapid ozone decline with 95 percent depletion typically happens during September, but this year the phenomenon remained for two extra weeks and reached nearly 100 percent on Oct. 15.
The first record of severe ozone depletion was recorded in the 1980s. Scientists say that the Antarctic ozone layer usually expands during August to September because of the high levels of CFCs and bromine in the atmosphere.
Under the 1987 Montreal protocol, the use of ozone-depleting substances that were released by spray cans and refrigerators were banned all over the world. The abundance of dangerous and unabsorbed ozone in the Earth's surface could lead to skin cancer and other diseases.
Meanwhile, Braathen said that even though the Montreal protocol is working well, the planet will still continue to experience the expansion of Antarctic ozone holes until about 2025 due to weather conditions and the presence of ozone-depleting substances in the atmosphere.
