Paper 1 - FRS 136: Living in a Polluted Greenhouse...

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FRS 136: Living in a Polluted Greenhouse Professor  Rik Sengupta Revisiting the Montreal Protocol: Lessons for Tomorrow The Background The Montreal Protocol became something of a logical “next step” in a series of events  revolving around one of the most chilling catastrophes the world has ever faced: ozone  depletion. Ozone, the allotrope of oxygen that absorbs harmful ultraviolet light from the sun  and therefore stops many of these harmful rays from reaching the earth’s surface, is present  in relatively large concentrations near the stratosphere. However, unknown to human beings,  this so-called “ozone layer” had been slowly getting destroyed by “ozone-depleting  substances” or ODS, a fact that was so unanticipated that the discovery of this fact took the  entire world by surprise. Before the mid-1970s, common refrigerants and many other  household substances that gave off CFCs (chlorofluorocarbons) and other similar substances  like halon were used widely; they were non-toxic, and were considered to be completely safe  and reliable. In the mid-70s, it was hypothesized that each molecule of these CFCs reached  the stratosphere, got excited by the ultraviolet rays of the sun, gave off a chlorine atom, which  singlehandedly destroyed thousands of ozone molecules 1  by means of a continuous cycle.  Various confirmations of this theory and the discovery of the existence of the “ozone hole”  in Antarctica cumulated in the entire world taking collective action, which led to the  remarkable success of the Montreal Protocol and its subsequent amendments, a phenomenal  demonstration of “common but differentiated responsibility” 2 . The Montreal Protocol was so  successful that it has been described as “perhaps the single most successful international  agreement to date” by Kofi Annan 3 . 1 1 molecule of CFC can destroy up to 100,000 molecules of ozone by means of continuous cycles. 2 Andersen, Stephen and Sarma, K. Madhava, Protecting the Ozone Layer: the United Nations History (London: Earthscan Publications, 2002), 351.
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The Success The Signs In 1973, work by chemists Frank Rowland and Mario Molina at the University of California  revealed some very startling facts. They studied the impact of CFCs on the atmosphere, and  discovered that at least one of the C-Cl bonds was excited by the ultraviolet rays from the sun  in the stratosphere, and as a result CFCs gave off a high-energy chlorine atom. Based on this  finding, the two chemists hypothesized that this had an adverse effect on the ozone layer –  because a single energized chlorine atom (which is highly reactive) can catalytically 
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Paper 1 - FRS 136: Living in a Polluted Greenhouse...

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