The Ozone Layer, and What Destroys It
Chapter One Hundred Thirty-Six
Syllabus topic 6, "Trans-boundary Pollution Hazards"
Pages 470 to 473 of 663
In one line
A thin band of ozone twenty kilometres up absorbs the ultraviolet radiation that would otherwise sterilise the surface of the planet, and for forty years we manufactured the chemicals that destroy it.
The science a lawyer needs
What ozone is. A molecule of three oxygen atoms. About ninety per cent of it sits in the stratosphere, roughly fifteen to thirty-five kilometres up. If the whole stratospheric layer were brought to the surface at ordinary pressure it would be about three millimetres thick.
What it does. It absorbs ultraviolet radiation in the band called UV-B, which damages DNA. Without it, terrestrial life as it exists would not be possible.
What destroys it. Chlorine and bromine atoms, released when certain manufactured compounds drift up to the stratosphere and are broken apart by ultraviolet light. The compounds are stable, which is what made them commercially attractive and what allows them to reach the stratosphere intact.
Why it is catalytic, and why that matters legally. A single chlorine atom destroys ozone and is regenerated, so it destroys again, thousands of times, over years. The harm from one release therefore continues for decades and is out of all proportion to the quantity released. That is the physical fact that justified a precautionary regulatory approach before the harm was proved.
The compounds. Chlorofluorocarbons, used as refrigerants, aerosol propellants, solvents and foam-blowing agents; halons, used in fire suppression; carbon tetrachloride; methyl chloroform; methyl bromide, used as a soil fumigant; and hydrochlorofluorocarbons, the first-generation substitutes, which are less damaging and not harmless.
Ozone depletion potential is the measure: the damage a substance does relative to a reference chlorofluorocarbon. It is what the Montreal Protocol's control schedules are calculated in, and it is why the Protocol regulates a calculated level rather than a tonnage.
The chronology
| Year | Event |
|---|---|
| 1930s | Chlorofluorocarbons developed and commercialised as safe, non-toxic, non-flammable refrigerants |
| 1974 | The hypothesis published that chlorofluorocarbons could destroy stratospheric ozone |
| 1976 | UNEP's Governing Council takes up the question |
| 1977 | A World Plan of Action on the Ozone Layer, and a Coordinating Committee |
| 1981 | UNEP's Governing Council authorises negotiation of a framework convention |
| 1985 | The Vienna Convention adopted in March; the Antarctic ozone hole reported in May |
| 1987 | The Montreal Protocol adopted |
| 1990, 1992, 1997, 1999, 2007 | Successive adjustments and amendments accelerating the phase-out and adding substances |
| 2016 | The Kigali Amendment, adding hydrofluorocarbons |
The order of the two 1985 events is the point. The Convention was adopted before the hole was reported, on a hypothesis and a precaution. Had the negotiators waited for proof, the framework would not have existed when the evidence arrived, and the Protocol could not have been made in two years.
That is the strongest argument for precaution available anywhere in this subject, and it is a matter of dates rather than of theory.
The rest of this chapter
Module one is free. The rest of LL.M. Environment and Legal Order Semester 2 is part of the bundle.
You are reading a chapter from a later module. Everything in module one of every subject stays free, and so does every question paper and the syllabus.
See the semester for ₹798 Already bought it? Sign in
Free either way: question papers, the syllabus, and module one of every subject.
The rest of this subject
These notes are cut from the University's printed syllabus. Open the syllabus itself, or the past papers, for the same subject.