An international agreement to phase out chemicals which attack the Earth’s vital ozone shield celebrates its 25th anniversary as a showcase for successful global environmental cooperation, “protecting our atmosphere for generations to come.”
The Montreal Protocol on Substances that Deplete the Ozone Layer, which was signed 16 September 1987, has prevented the destruction of the ozone layer which protects Earth from the harmful ultraviolet rays of the sun.
“With the global phase-out of 98% of ozone-depleting gases in consumer, industrial and agricultural products, the ozone layer is now on track to recover over the next five decades,” said U.N. Secretary-General Ban Ki-moon.
“Millions of cases of skin cancer and eye cataracts, as well as the harmful effects of ultraviolet radiation on the environment, have already been avoided. The Protocol has also catalyzed considerable innovation in the chemical and equipment manufacturing industry, resulting in more energy-efficient and environmentally friendly refrigeration systems,” said Ban Ki-moon in a message to mark the International Day for the Preservation of the Ozone Layer.
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 hydrochlorofluorcarbons (HCFCs) has increased, prompting an agreement in 2007 to accelerate the phase-out of HCFCs, which are commonly used in air conditioning. HCFCs are also powerful greenhouse gases.
“Given that many substances that deplete the ozone layer are also potent greenhouse gases, the Montreal Protocol has proved to be a double bonus for our atmosphere and climate system,” said World Meteorological Organization Secretary-General Michel Jarraud.
“The benefits will be felt by our children and our children’s children,” he said.
“The monitoring activities of WMO’s Global Atmosphere Watch program have strengthened our understanding of this relationship between ozone depletion and climate change. As we celebrate this 25th anniversary, we therefore pay tribute to the hundreds of scientists who have braved inhospitable terrain – including the Antarctic with temperatures down to -50 degrees Centigrade – to conduct the observations and research needed to understand our changing environment,” said Mr Jarraud.
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.
In its Antarctic Ozone Bulletin published on 14 September, WMO reported that the ozone hole increased rapidly during the first two weeks of September from about less than 10 million km2 to approximately 19 million km2. As of mid September the ozone hole is smaller than at the same time in 2011, but larger than in 2010. This is based on observations from the ground, from weather balloons and from satellites together with meteorological data.
The Antarctic ozone hole 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.
It is still too early to give a definitive statement about the development of this year's ozone hole and the degree of ozone loss that will occur. This will, to a large extent, depend on the meteorological conditions. However, the temperature conditions and the extent of polar stratospheric clouds so far this year indicate that the degree of ozone loss will be smaller than in 2011 but probably somewhat larger than in 2010. The ozone hole will most likely be smaller than in the record year of 2006.