Thursday, September 23, 2010

Differing States of Ozone Health

Scientific Assessment Compared to Secondary Source Representation

The National Post article “UN Scientists say Ozone Layer Depletion has Stopped”1 reports confidently that the ozone layer is being effectively protected by international regulation. This recent article is based on the World Meteorological Organization and the United Nations Environment Program’s “Scientific Assessment of Ozone Depletion: 2010”.2 This assessment reports the progress of protective measures towards global ozone levels in the context of the “Montreal Protocol on Substances that Deplete the Ozone Layer”. This protocol is an international treaty regulating the emission of chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). Although this assessment reports success in the international effort to stop the use of certain known ozone depleting substances (ODSs), it also takes care to note limitations to this success as well as obstacles in the way of preventing further harm. Most of these limitations are overlooked in the National Post’s report on this assessment. As well, direct contradiction exists between the two articles in their reporting of the ozone depleting properties of the commonly used refrigerant HCFC. The National Post article suggests elsewhere that the use of chemicals that are harmful to the ozone layer has been banned completely, where as the WMO/ UNEP assessment notes that the emission of some substances known to be detrimental to the ozone layer continues without regulation. The international effort to protect the ozone layer has made much progress, and this is noted in the WMO/ UNEP assessment. The National Post reported this progress, however it did so with little mention of the limitations duly noted in the primary report.

The National Post correctly reported that the WMO/ UNEP assessment states that overall global ozone levels are no longer decreasing. However, this statement is qualified in the WMO/ UNEP assessment with several conditions. Firstly, the relatively short sampling period of ozone levels compromises the application of the data collected. The assessment states that “Natural variability, observational uncertainty, and stratospheric cooling necessitate a long record in order to attribute an ozone increase to decreases in ODSs.”3 The WMO/ UNEP assessment notes further that although overall global ozone levels are no longer in decline, ozone depletion in the atmosphere above the Antarctic “far exceeds natural variability, and has occurred without exception since 1980.”4 It is noted also that the decay rate of several Ozone Depleting Substances may be longer than expected,5 making trend definition difficult. Although the WMO/ UNEP assessment of ozone depletion is not completely grim, the National Post attributes to it a degree of confidence in regulatory progress that is not expressed in the original report.

The WMO/ UNEP assessment mentions several times the ozone depleting properties of HCFCs, substances currently regulated under the Montreal Protocol.6 Although these substances do not exhibit properties of ozone depletion to the degree exhibited by CFCs, the use of HCFCs is currently being phased out in favour of more benign alternatives. The National Post reports that HCFCs are a powerful greenhouse gas, however it incorrectly describes HCFCs as being among “ozone friendly substances”.7 In contrast, the WMO/ UNEP report states that the use of HCFCs contributes to atmospheric chlorine levels, the elevation of which has been shown to cause ozone depletion. It notes further that levels of atmospheric chlorine are not declining at the expected rate because the increase in HCFC use has been greater than projected.8 The specific danger to the ozone layer associated with HCFCs is neglected by the National Post report.

A final glaring omission exists in the National Post report on the WMO/ UNEP assessment of ozone depletion. The WMO/ UNEP assessment takes care to note the ozone depleting properties of both nitrous oxide and methane, 9 substances currently unregulated by the Montreal Protocol. The effect on the ozone layer caused by the emission of these substances has the potential to be extremely detrimental. As stated in the primary assessment, “Under many IPCC future scenarios, it is projected that these gases will cause globally averaged ozone changes larger than those resulting from any of the ODS reduction cases explored in this chapter.”10 The ongoing unregulated emission of these gases casts a great shadow on current progress being made in facilitating ozone recovery. The National Post report on this assessment however fails completely to make any mention of this great limit to current regulation, stating simply that “The protective ozone layer in the earth’s upper atmosphere has stopped thinning and should largely be restored by mid century thanks to a ban on harmful chemicals”11 This statement implies that chemicals harmful to the ozone layer have been banned completely, however as noted in the WMO/ UNEP report, this is far from the case.

It is true that the WMO/ UNEP assessment of ozone depletion noted measured success in current regulation of ozone depleting substances. This point however was greatly overemphasized by the National Post’s summary of the assessment. Many of the conditions and cautions carefully detailed were omitted in favour of framing the assessment as one stating that current regulation is sufficient and successful. It can not be expected that a newspaper article is to carry the full informative potential of a scientific report. However, several great omissions as well as the outright contradiction regarding the ozone depleting properties of HCFC severely compromise the credibility of the National Post report. The WMO/ UNEP assessment of ozone depletion is not strongly positive or negative regarding human impact on the ozone layer. It recognizes damage done as well as measured success in mitigation of this damage. To make the declaration that “Ozone Depletion has Stopped” however, as stated in the very title of the National Post article, greatly misrepresents the information contained in the original WMO/ UNEP assessment. This assessment recognizes that the international effort to protect the ozone layer is one fraught with many difficulties and complications, an important detail not included in the National Post’s report.

Post by Dylan Harding

Works Cited:

1) Steiner, Achim. (September 16, 2010). UN Scientists say Ozone Layer Depletion has Stopped. The National Post.

2) World Meteorological Organization and the United Nations Environmental Programme. (2010). Scientific Assessment of Ozone Depletion: 2010”

3) WMO/ UNEP. Page 19.

4) WMO/ UNEP. Page 5.

5) WMO/ UNEP. Page 17

6) WMO/ UNEP. Page 2.

7) Steiner, Achim.

8) WMO/ UNEP page 12

9) WMO/ UNEP page 30

10) WMO/ UNEP page 30

11) Steiner, Achim.

Works Consulted:

United Nations Environment Programme. (2000). The Montreal Protocol on Substances that Deplete the Ozone Layer.

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