Ozone layer and ozone hole debate
The debate surrounding the ozone layer and the ozone hole primarily focuses on the depletion of ozone in the Earth's stratosphere, which is critical for filtering harmful ultraviolet (UV) radiation from the sun. Ozone (O₃) exists naturally but has been significantly affected by human activities, particularly through the release of chlorofluorocarbons (CFCs) used in various industrial applications. The discovery of a substantial thinning of the ozone layer over Antarctica in 1985 sparked global concern and led to international agreements like the Montreal Protocol, which aimed to phase out CFCs and other ozone-depleting substances.
While some scientists argue that ozone depletion could be part of a natural cycle, there is a widespread consensus that human actions have exacerbated the problem. The implications of ozone depletion are serious, with increased UV exposure linked to higher rates of skin cancer, cataracts, and damage to vital ecosystems, including phytoplankton, which are crucial to the ocean food web. Continuous monitoring and research have shown that, although there are fluctuations in the size of the ozone hole, there is a general trend towards recovery, attributed to the global efforts to reduce CFC emissions.
The ongoing discussion also touches on ethical considerations regarding the responsibilities of developed versus developing nations in addressing ozone depletion. As the world moves towards potential recovery of the ozone layer by mid-century, the connection between ozone depletion and climate change remains an important area of study, linking atmospheric conditions and their impact on both human health and environmental stability.
Ozone layer and ozone hole debate
Ozone, a form of the element oxygen, forms naturally in the stratosphere and provides the Earth with a filter from ultraviolet radiation. Some human activities cause a decrease in the amount of ozone present, an effect that has been described as a hole in (more correctly a "thinning" of) the ozone layer.
Background
Ozone is a highly reactive form of oxygen. It is composed of three oxygen atoms in a molecule (O3) rather than the more usual two atoms (O2). Ozone is formed from diatomic oxygen where high energy is present. Near the Earth, ozone forms in high-temperature combustion processes, such as in automobile engines and in electrical sparks. In the stratosphere it forms because of high-energy ultraviolet radiation. Once formed, ozone is quick to react with other molecules. Near the Earth there are many molecules with which to react, and the ozone concentration remains low. In the stratosphere there are few molecules present, so the ozone concentration builds up and forms what is termed the ozone layer. Ozone also disappears naturally by decomposing to ordinary oxygen, so there is a natural limit to the concentration that accumulates, and a steady state occurs. The ozone layer is actually quite diffuse, and the ozone concentration is never very high.
Description, Distribution, and Concentrations
Since the mid-1950s, measurements of ozone concentrations in the atmosphere have been made regularly. In the early 1970s, analysis of the measurements suggested that something was causing a reduction in the concentration of ozone in the stratosphere, particularly in the region over the South Pole. Continued measurements confirmed a similar lowering over the North Pole area and a spreading of the effect over a larger area. Laboratory experiments show that molecular fragments containing unpaired electrons are effective in speeding the decomposition of ozone. This catalytic effect is particularly strong in the presence of small ice crystals, which are present in the stratosphere in the polar regions in winter.
Chlorofluorocarbons
Chlorofluorocarbons (CFCs) are a class of chemicals that have found wide use as propellants in aerosol cans, cleaning solvents for electronic circuit boards, and working fluids in air-conditioning and refrigeration. The stability of these molecules is a prime factor in their utility, but this property also allows the molecules to drift into the stratosphere when they are released. Most other escaping molecules react or are washed out by precipitation before they gain much height in the atmosphere. In the stratosphere, CFCs decompose by irradiation and form molecular fragments to which ozone is sensitive. CFCs are not the only artificial cause of ozone depletion, but they have been recognized as a major contributor.
The Importance of Ozone
Ozone is decomposed when the energy available in part of the ultraviolet region of the spectrum is absorbed by the molecule. When the energy is used in such a fashion, it is no longer present in the sunlight that comes through the stratosphere to the Earth. This type of energy, if it does make it to the Earth, is capable of causing the reaction of other molecules, including those of biological importance. The evidence is overwhelming that the primary cause of nonmelanoma skin cancers is chronic long-term exposure to ultraviolet light. Sunny Australia has the highest incidence of skin cancer in the world. Other human interactions may lead to melanoma skin cancers and cataracts.
Increased ultraviolet levels also cause cellular modifications in plants, including food crops, which may lead to their death. Of particular concern is the inhibition of photosynthesis in the phytoplankton that forms the base of the ocean food chain. The ozone layer acts as a filter to limit the Earth’s exposure to high-energy light. With a diminishing level of filtering, one would expect that there would be a global increase in the effects of overexposure to ultraviolet radiation.
The Ozone Debate
Some scientists contend that ozone depletion is a part of a natural cycle related to sunspot activity. Knowledge of what has happened in the distant past is circumstantial and not easy to interpret, but most scientists agree that human activities play a significant role in the current decrease in the ozone layer. In terms of the human contribution, CFCs have received the major attention, and their production was severely limited by international agreement in the 1987 Montreal Protocol and later revisions, and were banned in the United States. CFCs are no longer used for propellants, and their role as cleaners is all but over. However, their use as refrigerant fluids continues while economically viable, safe substitutes are being sought. People in developed countries have become extremely dependent on air-conditioning (nearly all large buildings are designed to be air-conditioned rather than open to the outside). The search for substitutes has proved difficult, with economic, safety, and environmental concerns all placing limits on what is acceptable.
Part of the controversy concerning banning CFCs is based on ethical considerations. Developed countries utilized CFCs to gain their positions; should they then prohibit the use of CFCs in developing countries? Should these countries not be allowed to reap the same advantages as others even if there is an environmental price to be paid? There are no easy, satisfactory answers to such questions.
International Day for the Preservation of the Ozone Layer
In 1985, the Vienna Convention was signed by twenty-two countries. Two years later, the Montreal Protocol was signed on September 16, a day which has been designated by the United Nations as International Day for the Preservation of the Ozone Layer. The theme for the day in 2008 was "Montreal Protocol: Global Partnership for Global Benefits." On International Day 2008, the World Meteorological Organization (WMO) released several statements on ozone and ozone-related matters, including the following by Ban Ki-moon, the secretary general of the United Nations.
After decades of chemical attack, it may take another fifty years or so for the ozone layer to recover fully. As the Montreal Protocol has taught us, when we degrade our environment too far, nursing it back to health tends to be a long journey, not a quick fix.
According to WMO, the 2008 Antarctic ozone hole was larger than the one of 2007. The observed changes in the stratosphere could delay the expected recovery of the ozone layer. It is therefore vital that all member states with stratospheric measurement programs continue to support and enhance these measurements.
Routine ozone measurements in all parts of the world, using surface-based spectrophotometers, balloon-borne sensors, aircraft, and satellites, have been made by the National Meteorological and Hydrological Services of WMO members and partners worldwide since the 1950s. In the 1980s, comprehensive measurements started under coordination of the WMO Global Atmosphere Watch (GAW). These measurements have been critical to the series of Scientific Assessments of Ozone Depletion published since the mid-1980s by WMO and the Ozone Secretariat of the United Nations Environment Programme, documenting progress made under the Vienna Convention for the Protection of the Ozone Layer (signed in 1985 by twenty-two countries). These assessments are released approximately every four years.
The Montreal Protocol on Substances That Deplete the Ozone Layer underpins efforts to combat depletion of the Earth’s fragile protective shield. It also contributes to combating climate change, because many of the chemicals controlled under the treaty also contribute to global warming. By phasing out CFCs and deciding to accelerate a freeze and phase-out of hydrochlorofluorocarbons (HCFCs), the treaty has provided two benefits at once. The UN secretary-general expressed the hope that "Governments will look at such results and feel empowered to act across a wide range of environmental challenges, and not only in prosperous times."
In August, 2008, WMO released its first of the biweekly series Antarctic Ozone Bulletin on the current state of stratospheric ozone in the Antarctic. These bulletins use provisional data from the WMO/GAW stations operated within or near the Antarctic, where the most regular and dramatic decreases in ozone occur.
According to the 2008 bulletin, the vortex was more circular than at the same time in 2007. The meteorological conditions observed indicate that the 2008 ozone hole was smaller than that of 2006 but larger than that of 2007.
The Antarctic ozone hole reaches its maximum intensity in late September/early October. In 2008, the ozone hole appeared relatively late. On September 13, 2008, the ozone hole covered an area of 27 million square kilometers. The maximum area reached in 2007 was 25 million square kilometers. Similar measurements were observed in subsequent years, with the largest recorded hole coming in October 2015. Spikes such as that are attributed to the effects of volcanic activity on the atmosphere. WMO and the scientific community continued to make ozone observations from the ground, from balloons, and from satellites, together with meteorological data, to keep a close eye on the ozone development and depletion.
In 2016 researchers released a report indicating that the size of the Antarctic hole in the ozone layer was significantly smaller in September 2015 than in September 2000, and on average had decreased over that time. This suggested that, despite occasional yearly spikes, the general trend was toward a reduction in the hole's size. The "healing" was attributed to the impact of long-term removal of CFCs and other ozone-damaging chemicals from use. A complete closure of the hole was forecast by about 2050 or 2060.
Ozone Depletion and Climate Change
Many scientists are increasingly aware of the possible links between ozone depletion and climate change. According to many studies, increased atmospheric concentrations of greenhouse gases (GHGs) may lead to warmer temperatures in the troposphere and at the Earth’s surface. However, in the stratosphere, at altitudes where we find the ozone layer, there will be a cooling effect. A cooling of the stratosphere in winter over the latter decades of the twentieth century and the first decade of the twenty-first century has indeed been observed, both in the Arctic and in the Antarctic. Lower temperatures enhance the chemical reactions that destroy ozone. At the same time, the amount of water vapor in the stratosphere has increased at the rate of about 1 percent per year. A wetter and colder stratosphere means more polar stratospheric clouds, which may lead to more severe ozone loss in both polar regions.
Together with the International Council for Science (ICSU), WMO coordinated the International Polar Year 2007–2008. Thousands of scientists collaborated to increase understanding of processes that take place in polar regions, including those of stratospheric ozone and ultraviolet radiation. In February, 2009, WMO and ICSU celebrated the closure of the International Polar Year in Geneva and released WMO’s State of Polar Research.
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