AGEC/FNR 406 LECTURE 18 What the ozone hole looks like to a statistician!

Atmospheric Change 1. Ozone depletion in stratosphere 2. Global warming and climate change Two major issues – four lectures

Stock vs. Fund Pollutants 1. Fund pollutants: environment has some assimilative capacity 2. Stock pollutants: environment has little or no assimilative capacity Economic importance is that stock pollutants continue to accumulate or are persistent: the problem is dynamic not static

Issues in atmospheric change: 1. Activities affect basic chemistry 2. Pollutants accumulate 3. Effects are global 4. Economic impacts may be severe 5. Consequences are uncertain

Ozone depletion Main issue: Ozone in stratosphere blocks UV Depletion of ozone was predicted in 1974 Depletion was first observed in 1985 More UV means… - skin cancer - lower agricultural yields - mutation in phytoplankton

Ozone hole 1. Annual variation normal 2. Less ozone now

Source: British Antarctic Survey, data online at

Ozone depletion: main cause Main cause of ozone depletion is worldwide use of fluorocarbons, especially cholorofluorocarbons (CFCs). CFCs are: catalysts to convert O 3 (“ozone”) to O 2 inert, and therefore persistent

Chemical Process: Destruction of O 3 by Cl 1.UV radiation breaks off a chlorine atom from a CFC (CFCl 3 )molecule. 2.The chlorine atom attacks an ozone molecule (O 3 ), breaking it apart and destroying the ozone. 3.The result is an ordinary oxygen molecule (O 2 ) and a chlorine monoxide molecule (ClO). 4.The chlorine monoxide molecule (ClO) is attacked by a free oxygen atom releasing the chlorine atom and forming an ordinary oxygen molecule (O 2 ). 5.The chlorine atom is now free to attack and destroy another ozone molecule (O 3 ). One chlorine atom can repeat this destructive cycle thousands of times. Source: National Center for Atmospheric Research-UCAR

CFCs: main uses Refrigeration Air conditioning Spray propellants Foam production Solvents Ubiquitous in industry and consumer products in 1960s, 70s, and 80s. Main benefit: inert

CFCs: main problems No breakdown ==> persistent in upper atmosphere (10-30 m.a.s.l.) CFCs are catalysts in converting O 3 to O 2 Annual decreases in ozone measured to be between 1-6%

Ozone depletion: consequences 1. More UV transmission 2. CFCs are greenhouse gases and therefore increase global warming 3. Less ozone has a cooling effect and therefore mitigates global warming Net effect on global warming ambiguous, but other negative effects are clear.

Ozone depletion: policy context MAC MDF CFC emissions $ The optimal level is near zero, so a ban is likely to be an efficient approach.

Montreal Protocol 1987 agreement signed by most nations amended in 1990 and 1992 Called for complete elimination of CFCs: - in industrialized countries by 1996 (done) - in developing countries by 2006 (still in progress)

CFC replacements (hydrochloroflurocarbons) Two issues: 1. HCFCs are also ozone depleting 2. Economic incentives to develop recovery systems but… since CFCs are still available in less developed countries, an incentive for illegal importation exists.

What Progress? “Perhaps the single most successful international agreement to date has been the Montreal Protocol.” - Kofi Annan, Secretary General of the United Nations But…according to NASA, from September 21-30, 2006 the average area of the ozone hole was the largest ever observed, at 10.6 million square miles.

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