Ozone hole location

Growth of the Antarctic ozone hole, located mostly over the continent of Antarctica, since 1979. The images were made from data supplied by total ozone-mapping spectrometers (TOMS). The color scale depicts the total ozone values in Dobson units. The lowest ozone densities are represented by dark blue. 

Figure 29 shows a recent picture of the ozone hole taken from space. Strictly speaking the use of the word hole to describe what happens to ozone in the Antarctic is an exaggeration. There is undoubtedly a massive depletion of ozone, particularly between 12 and 20 km in the Antarctic stratosphere (up to 100%) but the total column of ozone is depleted rather than removed altogether (see Figure 28). The exact location and size of the hole varies with meteorological conditions, but the area covered has increased over the past 10 years or so (see Figure 30). Currently, in the austral spring the hole extends over the entire Antarctic continent, occasionally including the tip of South America, covering an area equivalent to the North American continent (ca. 22 million km ) (see Figure 31).

Although Rowland and Molina had predicted depletion of ozone concentrations by these reactions, there were many who doubted their conclusions. The phenomenon that finally brought the problem to the attention of the world was the discovery of the ozone hole over the Antarctic in 1985. During the winter, a combination of air flow pattern and low temperature create stratospheric clouds of ice particles. The surface of these particles is an ideal location for reaction of NO2, OCl, and O3. These clouds contain nitric acid hydrate, formed by... 

Paul continued to make major contributions to stratospheric chemistry. For example, he explained how nitric acid clouds cause the Antarctic ozone hole. At the same time, he also turned his attention to the troposphere, which is the air layer that connects with the biosphere and where weather and climate take place. The troposphere is also prone to air pollution, while it is cleaned by oxidation reactions. The self-cleaning capacity relies on the presence of reactive hydroxyl radicals that convert pollutant gases into more soluble compounds that are removed by rain. The primary formation of hydroxyl radicals in turn is from ozone. While most ozone is located in the stratosphere, protecting life on Earth against harmful ultraviolet radiation from the Sun, a small amount is needed in the troposphere to support the self-cleaning capacity. While previous theories had assumed that tropospheric ozone originates in the stratosphere, Paul discovered that much of it is actually chemically formed within the troposphere. The formation mechanism is similar to the creation of ozone pollution in photochemical smog . 

Third, even where it is clear that a particular type of chemical has caused a particular incident of damage, and we can identify who was causally responsible for the existence of that chemical (if not necessarily its presence in a particular location), the first condition, that the conduct transgressed a norm, is often not met. This is because those norms require only that foreseeable consequences are taken into account one is not responsible for consequences that could not have been foreseen. Thus Du Pont, the main manufacturer of chlorofluorocarbons (CFCs) — non-toxic and non-flammable chemicals that were used as a refrigerant and aerosol propellant for many decades — have not been held to account for the hole in the ozone layer caused by those chemicals because at the time the key decisions to manufacture them were made, in the 1930s, these effects could not have been predicted (Colborn et al, 1996, pp243-245). 

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