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Carbon dioxide in the atmosphere (2025)

David Suzuki gives a simple outline of climate change due to carbon dioxide in the atmosphere to introduce this topic. The second activity asks students to explain the data from the Keeling curve. Having studied these simple starters students are then asked to consider the recycling of other elements, not just carbon.

Lesson Description

Starting Question

Why is it said that respiration and photosynthesis form a major interaction between autotrophs and heterotrophs?

Activity 1 - CO2 concentration in the atmosphere.

There has been some heated debate about climate change in recent years. What are the arguments?

First listen to David Suzuki's explanation. Does it sound convincing?
David Suzuki explains Climate Change from VoVo Productions on Vimeo.

The data about carbon dioxide concentration of the atmosphere has been collected from the top of Hawaii, far away from cities and forests that produce and absorb carbon dioxide..

Watch this short video from the Office for Climate education Expert Video - the Keeling curve

Discussion Questions

  1. Between 1958 and 2024 what is the trend shown by the Keeling Curve ?

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  2. Why does the concentration of CO2 go up and down throughout the year?

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  3. Why do you think Keeling chose Mauna Loa and Antarctica to measure atmospheric CO2?

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  4. Why does the concentration of CO2 increase over time?

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Click the eye icon to display some suggested answers

Discussion Questions

  1. Between 1958 and 2024 what is the trend shown by the Keeling Curve ?

    The Keeling curve shows an increasing carbon dioxide centration, there is a positive correlation.
     
  2. Why does the concentration of CO2 go up and down throughout the year?

    The balance of the carbon cycle changes in summer and winter.
    In summer there is more photosynthesis, so there is more net flux of carbon away from the atmosphere,
    In winter there is less photosynthesis, but little change in the carbon dioxide producing processes, so more flux towards the atmosphere.
     
  3. Why do you think Keeling chose Mauna Loa and Antarctica to measure atmospheric CO2?

    Mauna loa is a mountain on Hawaii, far from variable sources of carbon dioxide, like traffic, industry, or other human activity.
     
  4. Why does the concentration of CO2 increase over time?

    Fossil fuels contain carbon that was trapped by plants from the atmosphere millions of years ago.
    When we burn fossil fuels, or deforest mature forests, we release carbon from these sinks into the atmosphere. Adding carbon dioxide.

Activity 2 - Explaining the keeling curve

Answer the questions shown below

  IB style questions about the Keeling curve.

Activity 3 - Recycling of all chemical elements

The Keeling curve shows the cycling of carbon dioxide in the atmosphere on a global scale, in summer it falls and in winter it rises.

All elements used by living organisms, not just carbon, are recycled and decomposers play a key role.

Research this article about the recycling of element in 'biogeochemical cycles'

Libretext Biology - Biogeochemical cycles

  • Make bullet point notes about three of the elements mentioned in the article.
  • For each cycle, Carbon, Nitrogen, Sulfur, and Phosphorus, find a quote from the text that explains why the cycling of this element is important.

 Teacher only box

This is a nice introduction to Mouna loa in Hawaii where Keeling collected the data for carbon dioxide concentrations..

This is a nice video about Mr Keeling himself and his CO2 collection methods.

There are model answers here: Keeling curve model answers

Another good resource, but as it is focused on Arctic (from the old guide) I have left it out of the lesson details above.

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