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 D

Question

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.

UnlockIAS · Accepted Answer

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.

Why the other options are wrong — (a) 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.  (b) 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.  (c) 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.

Concept: 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.

State PCS 2023 Q18 — Environment & Ecology PYQ with Answer

State PCS 2023 Q18 — Environment & Ecology PYQ with Answer