--- title: "What does burning fossil fuels do to the carbon cycle?" subtitle: "Year 9 Earth and space · The carbon cycle · Lesson 4" --- # What does burning fossil fuels do to the carbon cycle? **Name:** {{field-24}} **Date:** {{field-15}} **Class:** {{field-15}} > **Key question:** Coal is a forest from 300 million years ago. Burning it takes seconds. :::teacher-note **In one sentence:** Students explain that burning fossil fuels moves carbon from the geosphere to the atmosphere and why this is a net addition to the air's carbon store (AC9S9U03, node 4). **Students should be able to say:** I can explain where the carbon in fossil fuels comes from. I can explain why burning them raises CO₂ in the air even though natural flows are bigger. I can describe where the extra carbon goes. **Width:** the unmarked parts are the floor every student does (Engage, Explore, Explain, Evaluate). Typical and Wider sections add contexts, not difficulty. Students work in the online tutorial alongside this sheet. ::: ## Engage :::keep-together **Plants take about 120 billion tonnes of carbon out of the air each year. Burning fossil fuels adds about 10. What do you predict happens to the CO₂ in the air?** ☐ It falls ☐ It rises: the natural flows balance each other, so the extra 10 builds up ☐ Nothing: 10 is tiny next to 120 ☐ It rises by exactly 10 every year My prediction, and why: {{lines-3}} ::: :::teacher-note **What happens:** It rises. The 120 out is matched by about 120 back in, so the extra 10 has nowhere to go except partly into the oceans and plants. Roughly half stays in the air. ::: ## Explore Try it on the board in the tutorial. Was your prediction right? What was different? {{lines-2}} ## Explain: from the geosphere to the air :::keep-together ### Where it was **Where is the carbon in coal, oil and gas stored before it is burned?** ☐ In the geosphere: plants and tiny sea creatures buried millions of years ago ☐ In the atmosphere ☐ In the oceans ☐ Nowhere: burning creates carbon ::: :::teacher-note **Answer:** In the geosphere: plants and tiny sea creatures buried millions of years ago ::: :::keep-together ### Why it adds up **Why does burning fossil fuels raise CO₂ in the air, when natural flows are so much bigger?** ☐ Fossil fuel carbon is a different kind of carbon ☐ It releases in years carbon that took millions of years to store, and the natural flows were already balanced ☐ It stops photosynthesis ☐ It doesn't: the rise is natural ::: :::teacher-note **Answer:** It releases in years carbon that took millions of years to store, and the natural flows were already balanced ::: :::keep-together ### Where it went **On the board, about what fraction of the carbon burned ended up staying in the air? (Enter a percentage.)** Answer: {{field-15}} ::: :::teacher-note **Answer:** 60 In the model, roughly 60%; the rest was taken up by the oceans and by plants. In the real world, about 45% of each year's emissions stays in the air. ::: :::keep-together ### Why it matters **Why does more CO₂ in the air matter for Earth's temperature?** ☐ CO₂ thins the ozone layer, letting in more sunlight ☐ CO₂ is a greenhouse gas: it absorbs some of the heat Earth gives off, so more CO₂ slows heat escaping to space and Earth warms ☐ More CO₂ blocks sunlight, so Earth cools ☐ CO₂ comes out of chimneys hot, and that heat warms the air ::: :::teacher-note **Answer:** CO₂ is a greenhouse gas: it absorbs some of the heat Earth gives off, so more CO₂ slows heat escaping to space and Earth warms ::: :::typical ## Elaborate: starting from today :::keep-together ### What it took **What did you have to do to keep the air's CO₂ steady?** ☐ Nothing ☐ Cut burning to only what the oceans and plants can take up: much less than today ☐ Stop burning completely: any burning at all makes CO₂ rise ☐ Burn more ::: :::teacher-note **Answer:** Cut burning to only what the oceans and plants can take up: much less than today ::: ::: :::wider ## Elaborate: a cool burn and a coal fire :::keep-together **A cool burn of grassland and burning coal both release CO₂. Why do they affect the carbon cycle differently over decades?** ☐ Grass regrows within a year or two, taking the carbon back; coal's carbon was locked away for millions of years and won't return soon ☐ Grass smoke has no carbon ☐ There's no difference ☐ Coal releases oxygen ::: :::teacher-note **Answer:** Grass regrows within a year or two, taking the carbon back; coal's carbon was locked away for millions of years and won't return soon ::: ::: ## Evaluate: look back Write one sentence: "At first I thought… Now I think… because…" **Revision summary** - **Fossil fuels** are carbon stored in the **geosphere** over millions of years. - **Combustion** moves it to the **atmosphere** in years: a new flow added to a balanced cycle. - Oceans and plants take up part of it (in the real world a bit over half); the rest builds up, so **CO₂ in the air rises** (280 ppm before 1800, about 420 ppm today). ## Exit ticket :::keep-together **Plants and the oceans take up about half of the CO₂ we add each year. Why does CO₂ in the air still keep rising?** {{lines-3}} ::: :::teacher-note **Answer:** Burning moves carbon stored in the geosphere over millions of years into the air in years. The natural flows were balanced, so the half that plants and oceans don't take up builds up, year after year. :::