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Climate Change – Causes and Effects: No, it really is greenhouse gases – climate change causes living graph

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20 minutes

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Methodology & teacher’s notes

This activity graphically demonstrates to students the extent different causes (or scientifically known as ‘forcings’) of climate change since we have began keeping temperature observations. The way the data has been visualised for this activity has been simplified from extensive research and climate modelling by NASA.

  1. Take students through the Bloomberg interactive “What’s Really Warming the World?”. Take as much time as you want to both consolidate learning in the previous activity (#3) and allow discussion. Tip: if the yellow banner at the bottom of the webpage is obstructive, you can change the browser zoom to 80% by pressing Ctrl and – (minus) on your keyboard. Here are some helpful notes:
    1. Observed temperatures are in Fahrenheit. +2°F is roughly +1.2°C.
    2. These are ‘temperature anomalies’, which is the difference from an average – more info is given towards the bottom of the webpage under ‘A Word About Temperatures’
    3. ‘Orbital changes’ are the Milankovitch cycles – you can see that over short time scales, there is very little influence on climate. This is a key point: the current rate of climate change is unprecedented
    4. Solar’ is changes in radiation received from the sun. There are many different cycles, with the most famous being the 11-year sunspot cycle
    5. Volcanic eruptions do not produce as much CO2 as humans. Interestingly, very large eruptions such temporarily cool the climate. The cooling effect of the 1883 Krakatoa and 1991 Pinatubo eruptions can be seen
    6. Putting all the natural factors together show that if these were the only factors, then the world should not be seeing a warming trend at all
    7. Changing land use (including deforestation) shows a slight cooling effect. Note that this does not mean that cutting down trees cools the climate, but that a cleared area reflects more of the sun’s energy back out into space (the albedo effect). Deforestation does mean that less CO2 is absorbed and so stays in the atmosphere, increasing the warming impact of greenhouse gas emissions. This is a good video you can watch yourself, or have the students watch if you have time.
    8. Students do not need to know about ozone, but you can use this to clear up the misconception that the hole in the ozone is partly to blame for climate change. The ozone hole and ozone as a greenhouse gas are two different issues.
    9. While students don’t need to know the details about human-produced aerosols, they are worth noting that they have a cooling effect, but they are harmful in their own way and don’t balance out the impact of greenhouse gases, and so not a solution to a warming planet.
    10. Put all the human factors (forcings) together, including the biggest contributor of greenhouse gases, then you can see what is to blame for current warming.
    11. An IPCC special report released in 2019 estimates around 23% of human-caused emissions come from forestry, agriculture and other land uses. This includes deforestation.
  2. Hand out copies of the Causes of climate change living graph worksheet – one each per student. Students to draw lines from the annotations and point to appropriate places on the graph – the image below gives possible answers.

Challenge students to add some of their own annotations based on the interactive graph/video that you showed before-hand. The overall message is, when scientists combine all the ‘forcing’ lines, they statistically match the observed temperature exceptionally well. And the biggest factor of the rise, by far, is greenhouse gases.

References, sources & credits

World Resources Institute: “7 Things to Know About the IPCC’s Special Report on Climate Change and Land”  (accessed April 23 2024)

Further reading

Skeptical Science: “What does past climate change tell us about global warming?” (accessed April 23 2024)

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