September 15, 2012
International Ozone Day – Antarctic Ozone Hole Is Getting Smaller
April Flowers for redOrbit.com - Your Universe Online
The United Nations reported Friday that the hole in the ozone layer is expected to be smaller this year over the Antarctic than last year. They claim this illustrates how a ban on harmful substances has slowed ozone depletion.
The ozone layer in the Earth's atmosphere contains relatively high concentrations of ozone (03). This layer is found mainly in the lower portion of the stratosphere and absorbs 97 — 99% of the Sun's medium frequency ultraviolet light, which potentially damages exposed life forms on Earth.
In the early 1980s, using a combination of ground-based and satellite measurements, scientists began to realize that Earth´s natural sunscreen was thinning dramatically over the South Pole each spring.
The Antarctic hole is still larger than it was in 2010, and a complete recovery is still a long way off. The Antarctic ozone hole, which currently measures 19 million square kilometers, most likely would be smaller this year than in the record year of 2006, it said. The annual occurrence typically reaches its maximum surface area during late September and maximum depth in early October.
September 16, International Ozone Day, will mark the 25th anniversary of the Montreal Protocol on Substances that Deplete the Ozone Layer, an international agreement to phase out chemicals that attack the Earth´s vital ozone shield. The Protocol 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 per cent 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.
Much of the ozone destroying chemicals, such as chlorofluorocarbons (CFCs), previously present in products such as refrigerators and spray cans, has been phased out under the Montreal Protocol. Demand for replacement products, such as hydrochlorofluorocarbons (HCFCs), has increased. HCFC's are powerful greenhouse gases in their own right and this increased demand prompted an agreement in 2007 to accelerate the phase-out of HCFCs.
“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 (WMO) Secretary-General Michel Jarraud. “The benefits will be felt by our children and our children´s children,” he said.
The WMO is a specialized agency of the UN and as such is the UN's authoritative voice on the state and behavior of the Earth's atmosphere, its interaction with the oceans, the climate it produces and the resulting distribution of water resources. With 189 member states and territories as of 2009, WMO plays a leading role in international efforts to monitor and protect the environment through its programs. In collaboration with other UN agencies and the National Meteorological and Hydrological Services, WMO supports the implementation of a number of environmental and is instrumental in providing advice and assessments to governments on related matters. These activities contribute towards ensuring the sustainable development and well-being of nations.
“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.
The Montreal protocol has been a "great success", U.N. weather agency expert and WMO's senior scientific officer for atmospheric research Geir Braathen told a news briefing.
"This has prevented a major environmental disaster and globally ozone depletion has leveled off. We haven't really seen any kind of unequivocal ozone recovery yet," he said.
Despite the success of the Protocol for cutting production and consumption of these chemicals, the chemicals have a very long atmospheric lifetime. It will take several decades before their concentrations are back to pre-1980 levels. The chemical saturation of Antarctic stratosphere reached a maximum around 2000 and is now decreasing at a rate of about 1% per year.
Over the past ten years, stratospheric ozone in the Arctic and Antarctic regions is no longer decreasing, but it has not yet started to recover. The ozone layer outside the Polar regions is projected to recover to its pre-1980 levels before the middle of this century. However, the ozone layer over the Antarctic is predicted to recover around 2040. On the other hand, because of the impact of greenhouse gas warming, the ozone layer over the tropics and mid-southern latitudes may not recover for more than a century, and perhaps not ever.
In its Antarctic Ozone Bulletin published September 14, WMO reported that the ozone hole increased rapidly during the first two weeks of September from 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 combined 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. Year-to-year variations in area and depth are caused by variations in stratospheric temperature and circulation. Colder conditions result in a larger area and lower ozone values in the center of the hole.
It is still too early to make a definitive statement about the development of this year's Antarctic ozone hole and the degree of 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.
In the Arctic, record ozone damage was reported in the stratosphere in 2011, but levels normalized in 2012, Braathen said.