Healthy Atmosphere is theme of Ozone Day
“A Healthy Atmosphere, the Future We Want” is the theme for this year’s International Day for the Preservation of the Ozone layer on 16 September.
The event coincides with the signing in 1987 of an international agreement known as the Montreal Protocol on Substances that Deplete the Ozone Layer, which protects Earth from the harmful ultraviolet rays of the sun.
“Extraordinary challenges require extraordinary responses. A generation ago, the world’s nations agreed to act definitively to protect the ozone layer, initiating an inter- governmental process that blazed new trails,” said U.N: Secretary-General Ban Ki-moon in a message to mark the occasion.
He said the “remarkable success story” of the Montreal Protocol was “a beacon of hope.”
“It provides protection for the ozone layer, significantly contributes to climate mitigation and reminds us that, faced with existential threats, the nations of the world are capable of cooperation for the common good,” said the U.N. Secretary-General.
WMO and its Global Atmosphere Watch network of observing stations monitors the state of the ozone layer and the Antarctic ozone hole . This is an annually recurring winter/spring phenomenon due to the existence of extremely low temperatures in the stratosphere and the presence of ozone-depleting substances. It typically reaches its maximum surface area during the second half of September and the maximum depth during the first half of October
WMO’s Antarctic Ozone Bulletin published 10 September, said the current ozone hole area was similar to the one in 2011 and larger than in 2010 and 2012. However, the onset of ozone depletion varies considerably from one year to the next, depending on the position of the polar vortex and availability of daylight after the polar night.
Many ozone-destroying chemicals, such as the chlorofluorocarbons (CFCs) once present in products such as refrigerators and spray cans, have been phased out under the Montreal Protocol. However, demand for replacement substances including hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) for use in refrigerators and air conditioners has increased. Both HCFCs and HFCs are also very powerful greenhouse gases.
In an agreement reached 9 September, leaders of the powerful G-20 countries pledged to work through the Montreal Protocol to phase out HFCs in order to combat global warming.
Despite the success of the Montreal Protocol in cutting the production and consumption of ozone-destroying chemicals, these chemicals have a long atmospheric lifetime and it will take several decades before their concentrations are back to pre-1980 levels. The amount of ozone depleting gases in the Antarctic stratosphere reached a maximum around year 2000 and is now decreasing at a rate of about 1% per year.
Over the past decade, stratospheric ozone in the Arctic and Antarctic regions as well as globally is no longer decreasing, but it has not yet started to recover either. The ozone layer outside the Polar regions is projected to recover to its pre-1980 levels before the middle of this century. In contrast, the ozone layer over the Antarctic is expected to recover much later.