In relation to Ozone which statements are true ? A. Ozone is called protection shield of the Earth. B. In 1985 it was clear that Ozone layer has holes. C. 16th September is celebrated as World Ozone Day. D. In 1989 chemicals responsible for Ozone depletion are banned to utilize.
- (1)Only A, B and C
- (2)Only B, C and D
- (3)Only A, C and D
- (4)All the above
Correct — option (4), 'All the above'. Take the four statements, labelled A to D in the English column, one at a time. Statement A is the standard description of the ozone layer: ozone, the three-atom form of oxygen, is concentrated in the stratosphere roughly fifteen to thirty-five kilometres up, and it absorbs the shorter ultraviolet wavelengths that would otherwise reach the surface, so life on land depends on it and it is universally described as the earth's protective shield. Statement B is right on its date. In May 1985 Joseph Farman and his colleagues of the British Antarctic Survey published in Nature the measurements from Halley Bay showing a deep springtime loss of ozone over Antarctica, and it was that paper that made the ozone hole a known fact rather than a theoretical prediction; the Vienna Convention for the Protection of the Ozone Layer was adopted in the same year. Statement C is correct: 16 September is observed as the International Day for the Preservation of the Ozone Layer, commonly called World Ozone Day, the date being the anniversary of the signing of the Montreal Protocol in 1987. Statement D is correct in the sense it intends: the Montreal Protocol entered into force on 1 January 1989, and from that date its control schedules began to bind the parties to reduce and then eliminate the manufacture and use of the chlorofluorocarbons and halons responsible for ozone depletion. Four statements, all sound, so the answer is the option that takes all of them. Note that statement D's English — 'are banned to utilize' — is awkward as printed, but its meaning is not in doubt.
- (1)Only A, B and C — This option accepts the first three statements and rejects statement D, the one about the ban on ozone-depleting chemicals from 1989. The rejection is probably a date reflex: the Montreal Protocol is remembered as a 1987 agreement, so a candidate who has learnt that single year may treat any other year attached to it as wrong. But a treaty is signed on one date and comes into force on another, and the Montreal Protocol entered into force on 1 January 1989, which is when its obligations began to operate. The distinction between adoption, signature and entry into force is worth holding for every international agreement in the syllabus, because MPSC uses all three dates.
- (2)Only B, C and D — This option rejects statement A, which is the least rejectable statement in the set — that the ozone layer shields the earth is the reason the whole subject is in the syllabus at all. A candidate arrives here only by misreading, most often by thinking of ground-level ozone, which is a pollutant and a component of photochemical smog, and concluding that ozone cannot be protective. The two are the same molecule in different places, and the difference is entirely one of altitude: ozone in the stratosphere absorbs ultraviolet radiation and protects life, while ozone at the surface irritates the lungs and damages crops. Good ozone up, bad ozone down, is the usual way of remembering it.
- (3)Only A, C and D — This option rejects statement B and so denies that the ozone hole was known in 1985. That was the year it became known: the British Antarctic Survey's Halley Bay measurements were published in May 1985, and the Vienna Convention was adopted in March of the same year, so 1985 is doubly fixed in the chronology. A candidate may hesitate because the depletion mechanism had been proposed a decade earlier, in the 1974 work of Rowland and Molina on chlorofluorocarbons, and may therefore feel that 1985 is too late a date. But the prediction and the observation are separate events, and the statement is about the observation.
The ozone story is the one clear success in international environmental regulation, and it is worth learning as a sequence. Ozone is O3, formed and destroyed continuously in the stratosphere in a natural cycle, and the layer it forms absorbs ultraviolet-B and ultraviolet-C radiation, which damages DNA and causes skin cancers and cataracts. In 1974 Mario Molina and F. Sherwood Rowland argued that chlorofluorocarbons, then valued precisely because they were inert and non-toxic, would survive to reach the stratosphere and there release chlorine atoms which would destroy ozone catalytically; they shared the Nobel Prize for chemistry in 1995 with Paul Crutzen. In March 1985 the Vienna Convention created a framework for cooperation, and in May 1985 the British Antarctic Survey published measurements of a deep springtime ozone loss over Antarctica — the hole, produced by polar stratospheric clouds and the isolating polar vortex, which together let chlorine act with unusual efficiency. The Montreal Protocol was agreed on 16 September 1987, entered into force on 1 January 1989, and has since been strengthened repeatedly; 16 September is observed as World Ozone Day. The Kigali Amendment of 2016 extended the treaty to hydrofluorocarbons, which do not deplete ozone but are powerful greenhouse gases.
MPSC treats the ozone layer as a date-and-agreement topic more than as a chemistry topic, and the questions that result are almost always statement-combination items in which each statement carries a year, a date or a name. That makes them easy for a candidate with a timeline and hard for one without, because the four candidate years — 1974, 1985, 1987 and 1989 — are all genuine and all attached to different events. The other thing this family of questions tests is whether the candidate distinguishes stratospheric ozone from ground-level ozone, since a set of statements will often mix the two. Note that this question labels its statements with upper-case letters in the English column and with Devanagari letters in the Marathi column, and the options quote those labels, so the two columns' option texts are not interchangeable; a candidate must answer from the column he is reading. The paper's English also runs awkwardly in statement D, which is characteristic of this edition and does not affect the sense.
- Ozone, O3, is concentrated in the stratosphere between roughly fifteen and thirty-five kilometres and absorbs the shorter ultraviolet wavelengths, which is why the layer is described as the earth's protective shield.
- In May 1985 Joseph Farman and colleagues of the British Antarctic Survey published the Halley Bay measurements establishing a deep springtime ozone loss over Antarctica; the Vienna Convention was adopted in March of the same year.
- 16 September is observed as the International Day for the Preservation of the Ozone Layer, the anniversary of the signing of the Montreal Protocol in 1987.
- The Montreal Protocol entered into force on 1 January 1989, from which date its control schedules on chlorofluorocarbons and halons began to bind the parties.
- The depletion mechanism was proposed in 1974 by Mario Molina and F. Sherwood Rowland, who shared the 1995 Nobel Prize for chemistry with Paul Crutzen; the Kigali Amendment of 2016 extended the treaty to hydrofluorocarbons.
Hold three dates apart for every treaty in the syllabus: adoption, signature and entry into force. MPSC uses all three. Prediction and observation are separate too — Molina and Rowland proposed the mechanism in 1974; 1985 is when it was measured.
- Rejecting a correct statement because the year attached to it is not the single year one has memorised; a treaty's signature and its entry into force are different dates
- Confusing stratospheric ozone with ground-level ozone and concluding that ozone cannot be described as protective
- Treating 1974, when the depletion mechanism was proposed, as the date the ozone hole was observed, which was 1985
- Reading the Marathi column's Devanagari statement labels against the English column's options, when the two sets of labels are different
Ozone depletion is among the most frequently asked environment topics in state commission papers, and it is asked almost entirely through dates, days and agreements. Expect statement-combination questions of exactly this shape, with four short claims each anchored to a year or a date, and expect at least one of the statements to concern an observance such as World Ozone Day on 16 September. The Commission also likes to test the framework-versus-protocol distinction, so the relation between the Vienna Convention and the Montreal Protocol is worth holding, as is the parallel between them and the Rio Convention and Kyoto Protocol on climate. A single timeline with five entries, each carrying a year and one line on what happened, will answer most of what this topic can be asked to yield.
No directly related past PYQ was found.
- practice — not a real PYQ
The Montreal Protocol on Substances that Deplete the Ozone Layer was signed on 16 September 1987 and entered into force on which date ?
- (a)1 January 1989
- (b)16 September 1988
- (c)22 March 1985
- (d)1 January 1992
Answer(a) 1 January 1989 — the Protocol was agreed and opened for signature on 16 September 1987, the date now observed as World Ozone Day, and its obligations began to bind the parties from 1 January 1989. 22 March 1985 is the date of the Vienna Convention, the framework agreement under which the Protocol was later negotiated.
- practice — not a real PYQ
The existence of a deep springtime loss of ozone over Antarctica was established in 1985 by the published measurements of which body ?
- (a)The British Antarctic Survey
- (b)The World Meteorological Organization
- (c)The United Nations Environment Programme
- (d)The Intergovernmental Panel on Climate Change
Answer(a) The British Antarctic Survey — Joseph Farman and his colleagues published the Halley Bay measurements in Nature in May 1985, turning a theoretical prediction made by Rowland and Molina in 1974 into an observed fact. The IPCC was established only in 1988 and deals with climate change rather than ozone depletion.