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In this activity, students will use global carbon dioxide (CO2) concentration data since 1930 to plot major life milestones of themselves, their parents, and grandparents along a curve. Students will learn about trends over time and the long-lived nature of CO2 in the atmosphere, and discuss solutions to the problem.



  • This lesson is best done individually, so students can see their own life milestones on a single graph.
  • Students with more experience graphing can use spreadsheet software to graph the data in the original source CSV files.
  • For advanced students using the 1832 to 1958 data from Antarctic ice cores, use columns Mean Air Age, year A.D. and CO2, 20 year smoothed, ppm.
  • For advanced students using NOAA's Global Monitoring Laboratory CO2 annual mean data, use columns Year and Mean.


Your students have probably heard about climate change. Earth’s climate is always changing, but the difference is that right now, these changes are happening very quickly compared with the past. This is because humans have developed a large footprint on the planet and, for the first time, human activity is driving Earth’s climate to change on a global scale. Your students may have seen news reports about massive wildfires, droughts, floods, and hurricanes, all of which can be intensified by climate change.

Why is this happening? When going about our daily lives, humans often power our activities by combusting fossil fuels like oil and gas. This includes when we drive cars that use gasoline, when we heat our homes by burning oil or natural gas, and when we power our appliances using electricity generated by burning coal or natural gas. The combustion of oil and gas releases carbon dioxide (CO2) into the atmosphere. Because of this, CO2 levels in the atmosphere have increased almost every single year in recent history. The atmosphere already has CO2 in it, so this might not seem like a big deal. Also, we can’t see CO2, and it doesn’t smell bad (or have any smell at all), so it’s hard to notice that its concentrations are increasing.

This graph displays monthly measurements of CO2 in the atmosphere (average seasonal cycle removed). Credit: NOAA | For more Earth vital signs, visit NASA's Global Climate Change website

However, even if we can’t see or smell it, the increasing CO2 concentrations are having a big effect. CO2 acts as a greenhouse gas. This means that it absorbs and traps the heat from the Sun. Because CO2 does this, it has helped keep our planet warm and insulated us from the harshness of outer space for all of human history. The issue is that everything on Earth is in a balance. When one thing goes out of balance, it can be the domino that falls and then causes many other things to go out of balance. In the case of CO2, there’s now so much of it in the atmosphere that Earth’s temperature is rising faster than at any point in recorded history. Animals, plants, entire ecosystems, human health, and natural disasters are all hanging in the balance as CO2 keeps rising.

This graph illustrates the change in global surface temperature relative to 1951-1980 average temperatures. The 10 warmest years in the more than 140 years of recording all have occurred since 2000. The year 2020 ranks as the warmest on record. For more Earth vital signs, visit NASA's Global Climate Change website

We have many tools, including NASA satellite instruments, such as the Orbiting Carbon Observatories, or OCO, to help us measure how CO2 is increasing worldwide. Launched in 2014, OCO-2 is a satellite that maps Earth’s atmospheric carbon dioxide every 16 days. OCO-3 is an instrument attached to the International Space Station, so it is able to measure CO2 at different times of day, compared with OCO-2 that provides measurements at fixed times of day.

Watch this animation to learn about some of these tools, and see how CO2 has risen over the life of Sandra, a fictional NASA scientist.

How much has carbon dioxide increased in a lifetime? Credit: NASA | Watch on YouTube

The lesson below will lead your students through creating their own lifetime graphs of CO2 and comparing their graphs with graphs for older people in their lives. The lesson makes use of a spreadsheet of CO2 concentration data. The data in the spreadsheet were acquired from NOAA’s Global Monitoring Laboratory on Mauna Loa and the historical CO2 record based on Antarctic ice cores.


  1. Ask students what they know about greenhouse gases. Accept various answers including naming the main greenhouse gases (methane, carbon dioxide, nitrous oxide, water vapor, etc.) and their contribution to climate change.
  2. Ask students to explain why these gasses are known as greenhouse gases. Accept answers that indicate students understand the heat-trapping function of a gardening greenhouse.
  3. Explain to students that greenhouse gases occur naturally in the environment and help stabilize Earth’s atmosphere, but that they can also be created by human action. When too much of any of the greenhouse gases accumulates in Earth’s atmosphere, the Earth system can become imbalanced. (Such is the case with global warming.)
  4. Explain to students that they will be analyzing atmospheric carbon dioxide concentrations measured on Earth over time. Ask if they can name any sources of CO2
  5. Have them watch the video "How much has carbon dioxide increased in a lifetime?" and talk about the graph at the end. Discuss the trend. Note how Sandra’s life milestones are plotted along the graph. 
  6. Explain that we will each now make a graph like Sandra’s to see how CO2 has changed in our lifetimes. 
  7. Pick a year just slightly before when the students in the class were born and provide the students with the spreadsheet that notes average annual CO2 concentrations. Have each student plot the CO2 concentration data by year on a blank graph. (See page 2 of the student worksheet.)
  8. Just like Sandra did, have the students list 4-6 milestones in their lives and mark them on the graph.
  9. Ask students to share some of the milestones they picked with the whole class.
  10. Have the students calculate the percent increase in CO2 concentrations between their milestones. Remind students how to calculate this by subtracting the two measurements and dividing the difference by the lower of the two measurements. By what percent has the CO2 concentration changed during their lifetime? 
  11. Direct students to the first page of the student worksheet to find the time series of CO2 concentrations going back to 1930. Have them label the years in which they, their parents, and grandparents were born (or legal guardians, caregivers, neighbors, a favorite celebrity, etc.). Then have them calculate the percent increase in CO2 concentrations between one person’s birth to the next-oldest person’s birth. To do this, they can look up exact values in the spreadsheet.
  12. Ask students the following questions about their graphs.
    • How much did the CO2 concentration change between your parent’s or grandparent’s birth year and when they were your age? 
    • How does this compare to the change in your lifetime?


  • Discuss the causes of the CO2 increases between each of the milestones students have identified. Encourage them to think about human actions that contribute CO2 to the atmosphere.
  • In the video, Sandra uses science ideas to protect Earth and its resources.
    • What were some of the things she got involved in to protect Earth?
    • What are some ways students can get involved?
    • What would it take to reverse the trend of increasing atmospheric CO2?


  • Students should be able to read a Cartesian graph (rectangular coordinate graph), graph coordinate pairs, and identify trends.
  • Students should be able to name some sources of carbon dioxide.


Have students use an online carbon footprint calculator to calculate their family’s carbon footprint and determine ways they can decrease their footprint.

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