Science and Decisions: The Ozone Layer (Grade 8)
Free printable Grade 8 Science as a Human Endeavour reading comprehension on the ozone hole and the Montreal Protocol, and how communicating evidence changed government policy.
Science and Decisions: The Ozone Layer
Read the passage, then answer the questions. Every answer is in the text.
High above us, in a part of the atmosphere called the stratosphere, there is a layer of ozone gas. It matters because it absorbs most of the Sun's harmful ultraviolet radiation, the radiation that causes sunburn and skin cancer.
In 1974 two chemists, Mario Molina and F. Sherwood Rowland, published a paper with a warning. Chemicals called chlorofluorocarbons, or CFCs, were being used in spray cans, fridges and air conditioners because they were cheap, stable and did not catch fire. Molina and Rowland calculated that those same stable chemicals would drift up into the stratosphere, where sunlight would break them apart and release chlorine that destroys ozone. At the time it was only a prediction.
In 1985 scientists from the British Antarctic Survey, Joe Farman, Brian Gardiner and Jonathan Shanklin, published measurements taken at their Antarctic station. Each spring, ozone above Antarctica was dropping sharply. Newspapers called it the ozone hole. Their measurements turned a prediction into observed evidence, and the news spread quickly.
Governments acted faster than usual. In 1987 countries agreed to the Montreal Protocol, a treaty to phase out CFCs, and it came into force in 1989. Every member country of the United Nations has now agreed to it, which no other environmental treaty has achieved. Industry had to find replacement chemicals, which cost money, and some argued the science was not certain enough. In 1995 Molina and Rowland shared the Nobel Prize in Chemistry with Paul Crutzen for their work on how ozone forms and breaks down.
The decision affected Australia strongly. Australia has some of the highest ultraviolet levels in the world and among the highest rates of skin cancer, so the health risk was real here. Scientists now measure the ozone layer slowly recovering, and expect it to return to its 1980 condition around the middle of this century over most of the world, and later than that over Antarctica. It is one of the clearest examples of scientific evidence being communicated to the public and then changing what governments do.
- 1.Name two products that used CFCs.
- 2.Which part of the atmosphere holds the ozone layer?
- 3.What does the ozone layer do that matters for human health?
- 4.Which two chemists published the 1974 warning about CFCs?
- 5.Who published the 1985 measurements of the ozone hole, and where did they work?
- 6.Give one cost or objection the passage mentions to phasing out CFCs.
- 7.In what year did the Montreal Protocol come into force?
- 8.What do scientists expect to happen to the ozone layer over most of the world by about the middle of this century?
Accuracy and sources
These references support the historical wording and answer key on this worksheet.
- UNEP Ozone Secretariat, The Montreal Protocol — gives the 1987 agreement date, entry into force in 1989, and universal ratification by UN member states
- The Nobel Prize in Chemistry 1995 — confirms the prize shared by Paul Crutzen, Mario Molina and F. Sherwood Rowland for work on ozone formation and decomposition
- British Antarctic Survey, the ozone hole — documents the 1985 Farman, Gardiner and Shanklin paper reporting large springtime ozone loss over Antarctica
- Cancer Council Australia, UV radiation — supports the statement that Australia has very high UV levels and among the highest skin cancer rates in the world