Human activities affect the concentration of both stratospheric and tropospheric ozone.

Outline the differences in these two effects by completing the following table.

Images from space and measurements have allowed scientists to estimate changes in the ozone hole.

Figure 7: Changes in the ozone hole from 1979 to 2008.

Figure 7:

[Source: http://earthobservatory.nasa.gov/Features/EarthPerspectives/page3.php] Images and data courtesy NASA Ozone Hole Watch.]

Including reference to this data, evaluate the effectiveness of the Montreal Protocol (1987) in managing ozone depletion.

One mark for two or three correct responses and two marks for four correct responses.

No marks for only one correct response.
Do not accept only ‘health problems’.

[2 max]

Weaknesses [3 max]
after Montreal Protocol entered in effect ozone levels continued decreasing / stabilized for a few years before declining again;
agreement of Montreal Protocol was not followed by an immediate response / the banning of ODS occurred in stages / not all countries initially participated in the Montreal Protocol;
enforcing/policing implementation of the Montreal Protocol across all nations is difficult;
following banning of ODS/Montreal Protocol a black market trade continued in these substances;
Montreal Protocol did not stop further destruction of stratospheric ozone due to the long life spans of ODS;
the effects of the Montreal Protocol will take a long time to occur and for the ozone hole to reduce;

Strengths [3 max]
the ozone hole stabilized between around 1993 and 2008;
in 1988 ozone hole showed a significant decline/ results for 1988 are anomaly;
in 2002 ozone hole showed a significant decline/ results for 2002 are anomaly;
without the Montreal Protocol the ozone hole may have continued to increase at a faster rate/indefinitely/beyond 26.6 million km²;
Protocol has led to reduction in production/use of ODS (eg CFCs);
due to reduction in ODS, ozone levels are expected to recover in the future (eg some scientist predict that by 2080 ozone levels will return to 1950 levels/ by 2014 there were signs the ozone hole was starting to recover);
referred to as the most successful international environmental agreement /first universally agreed Protocol /agreed by all nations;
it provides a model/example for other global environmental protection initiatives;

Credit quantification of data eg: ozone hole increased by around 5 million km² between 1987 and 2008 compared to about 10 million km² between 1980 and 1986;

Appraisal / Conclusion [1 max] - clear statement which adequately considers both strengths and weaknesses of the Montreal Protocol and implies which side is stronger based on evidence provided.
N.B An isolated statement eg “the Montreal Protocol has been successful” or an unjustified opinion eg “I think the Montreal Protocol has been successful” should not be considered as a valid appraisal/conclusion. The appraisal/conclusion must be supported/justified by points raised that have addressed both sides of the argument.

Award max of 4 marks for responses that do not refer to the data.

[5 max]

Responses varied. A common error was to confuse stratospheric ozone with tropospheric ozone.

Responses varied widely. Very good responses were able to correctly apply their knowledge of the Montreal Protocol and ozone depleting substances to the trends observed within the data. Poor responses did not relate changes within the data to the year of the Montreal Protocol or confused Montreal with the Kyoto Protocol and greenhouse gas emissions.