Teacher Preparation

Overarching learning goal: By participating in this activity students recognise similarities between CFCs and CO₂, and the differences in how humanity has responded to their human induced abundance in the atmosphere. Students will also understand the effects of the Montreal Protocol on CFC emissions and consider what the possibilities and barriers are for using this as a model for managing CO₂ emissions.

Teacher content information: The ozone layer is the layer of upper atmosphere, from 15 to 35km above the Earth’s surface. If all of the ozone were compressed to the pressure of the air at sea level, it would be a few millimetres thick. This fragile blanket protects us from the sun’s ultraviolet radiation and allows life to exist on Earth’s surface.

Two scientists from the University of California, Molina and Rowland, published a paper in 1974 proving the link between chlorofluorocarbons (CFCs) and ozone depletion. CFCs were widely used in air conditioning, as refrigerants, aerosol propellants and solvents.

The hole in the ozone layer was discovered in 1985. The world’s leaders created the Montreal Protocol, which limited the use of CFCs from early 1987 leading to a total phase out by 1996. Molina and Rowland were presented with the Nobel Prize for Chemistry for their work in 1995.

Since its implementation in 1987, the protocol has been revised and strengthened several times. The success of the Montreal Protocol is a shining example of what can be done when our world leaders come together to act for good. Importantly, the companies who produced these harmful gases were readily able to shift production to different kinds of less harmful gases.

Kofi Annan, the former Secretary General of the United Nations, called it ‘Perhaps the single most successful international agreement to date.’

In 2003, scientists determined that the depletion of the ozone layer was slowing due to the ban on the use of CFCs. These CFCs have a very long atmospheric lifetime, ranging from 50 to 120 years.

The total recovery of the ozone from the impact of CFCs will take several generations. Some CFCs have been replaced by hydro-chlorofluorocarbons (HCFCs) that have since also been linked to man-made global warming.

The Montreal Protocol was tightened in September 2007, decreeing that production of these must be halted by 2020 in developed countries. Final savings of greenhouse emissions will be in the order of several billion tons. We have not solved our problem of ozone depletion, but we have made great steps towards it.

For more reliable information about climate change in Australia, visit the Climate Council.

The IPCC

The Intergovernmental Panel on Climate Change (IPCC) is the United Nations body for assessing the science related to climate change. It was created to:

provide policymakers (governments) with regular scientific updates about climate change;
highlight the impact climate change will have on the planet in the future; and,
offer some ideas about how to tackle the challenges of climate change's potential effects on the planet.

In 2021-22, the IPCC released their sixth assessment report. This is the most up-to-date physical understanding of the climate system and climate change.

The report makes a number of important points:

It is unequivocal that human influence has warmed the atmosphere, ocean and land.
Global surface temperature will continue to increase until at least mid-century under all emissions scenarios considered. Global warming of 1.5°C and 2°C will be exceeded during the 21st century unless deep reductions in CO2 and other greenhouse gas emissions occur in the coming decades (B1). The report describes five possible climate futures, where #1 is not great and #5 is extremely bad. If we want to keep global warming at less than two degrees, which the IPCC says is the best-case scenario, we need to reduce our CO2 and greenhouse gas emissions significantly and start right away.

'Net zero' or 'carbon neutral' are terms that refer to achieving an overall balance between greenhouse gas emissions produced and greenhouse gas emissions taken out of the atmosphere. Getting to net zero means we can still produce some emissions, so long as we're doing something else to reduce the greenhouse gases already in the atmosphere at the same time, kind of like balancing a set of scales (more info).

Psychological safety. The IPCC Report sets a hard challenge. While this real-world issue is essential for students to understand, there is no doubt it can make them feel sad or anxious about the future is becoming darker and scarier by the day. So, reassure students that we can have a hopeful and optimistic outlook on this report, rather than one of doom and gloom. Explain that optimism involves looking objectively at a situation and making a conscious decision to focus on the good (more info), and that hope is the belief that you can make an impact (more info). Explain to students that you are going to look ahead, identify what needs to be improved, and then work on the skills and confidence so that they can go out and do it. If you're interested in learning more about how to approach challenging topics around climate change and sustainability in your classroom through a Hope and Optimism lens, consider our PD course.

Student and classroom organisation:

Step 1.

Begin this activity by asking students to share what they already know about the ozone layer and the hole in the ozone layer. For example:

What and where is the ozone layer?
What does it do?
Where is the hole?
What caused the hole?
What effect did the hole have on life on earth?
What can be done to stop the spread of the ozone layer?

Record student discussion on the board, or use one of the following online tools to record discussion: Popplet or Padlet.

Step 2.

Ask student to look at the table on the Student Worksheet and create an animated graph describing the information in the table.

Extension: Ask students to research and compare the level of thinning in the ozone layer in different states in Australia. Again students should represent this data in an animated graph.

Step 3.

Recent studies suggest that the thinning of the ozone layer has stabilized and could even be starting to repair itself. Assuming that the spread of the thinning in the ozone has indeed peaked - at 27.5 million kilometers - ask students to calculate the average amount the ozone has reduced since 2000, and based on this calculation how long it will take to repair itself. Students should use the Student Worksheet to record answers.

Step 4.

The Montreal Protocol was signed by a number of countries in 1987. It is assumed that the signing of this protocol helped to drastically reduce the amount of CFCs being released into the atmosphere.

Considering this and the data presented in their graphs, ask students to work in pairs to draw some conclusion about CFCs and their lasting effect on our atmosphere. They should use a Venn Diagram to compare and contrast CO₂ and CFCs.

The idea behind creating this diagram is for students to realise that we are still dealing with the damage caused by CFCs prior to the Montreal Protocol, even though there has been an apparent improvement in the size of the hole. Students should be working towards the conclusion that both CFCs and CO₂ have a long lasting effect on our atmosphere, and that even if we reduce our current CO₂ emissions we will be dealing with the effects of these for a long time.

Reflection

The hole in the ozone layer is actually a good news story! In the 80s scientists proved that the CFCs we released were damaging the earth. Since then we have been phasing out CFCs and the damage we did is starting to repair itself.

Ask students to prepare for and conduct a debate around the question: Do you think the world can reach an agreement on CO₂ emissions that is similar to the successful Montreal Protocol?

Ask students to download and follow these debate guidelines (also available on the Student Worksheet). Conduct the debate and ask students to consider the reflection questions on the Student Worksheet following the debate.

Students should also answer the Reflection Questions on the Student Worksheet.

Homework/Extension

Ask students to research and briefly summarise the history of global climate change negotiations and to present this information as a timeline.

Weather Makers - Is the ozone layer a good news story?

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