The carbon cycle and climate change
Carbon moves constantly between air, living things, oceans and rock. For thousands of years the flows roughly balanced. Human activity has tipped that balance, and the evidence sits in the data.
Lesson overview
What you'll learn in this lesson
Understand the carbon cycle and the production of carbon dioxide by human activity and the impact on climate
Key learning points
- • The natural cycle
- • Sinks and long-term stores
- • What human activity added
- • Consequences and responses
This lesson at a glance
- 30 minutes
- 25 parts to scroll through
- 4 quick checks
- Marked quiz at the end
- Gentle pace: short sittings with pauses
Words to know
Scroll down — the lesson carries on below
Watch & discover
Part 1 of 25
Visual introductionPicture this
The carbon cycle and climate change
Carbon moves constantly between air, living things, oceans and rock. For thousands of years the flows roughly balanced. Human activity has tipped that balance, and the evidence sits in the data.
In a nutshell
Understand the carbon cycle and the production of carbon dioxide by human activity and the impact on climate
What you already know
Part 2 of 25
Before we start
What you already know
You should already know that respiration releases carbon dioxide and photosynthesis takes it in.
Key words
Part 3 of 25
Key words
Words you'll need today
- Carbon sink
- A store that absorbs more carbon than it releases.
- Combustion
- Burning a fuel, releasing carbon dioxide.
- Greenhouse effect
- Gases trapping energy re-radiated from Earth's surface.
- Sequestration
- Locking carbon away in a long-term store.
Reset break
Part 4 of 25
Pause
That's sitting 1 of 6 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Learning cycle
Part 5 of 25
Learning cycle 1 of 2
How carbon moves
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 6 of 25
Learn
The natural cycle
Photosynthesis removes carbon dioxide from the air and locks carbon into glucose. Respiration by plants, animals and decomposers returns it. Some carbon is stored for far longer: in wood, in soil, dissolved in oceans, and in rocks and fossil fuels formed over millions of years. The cycle is a set of flows between stores, not a single loop.
Explore the idea
Part 7 of 25
Learn
Sinks and long-term stores
Oceans and forests are the largest carbon sinks. Cold water dissolves carbon dioxide, and marine organisms build shells that eventually form rock. Peatlands hold huge quantities of carbon in waterlogged soil. Damaging a sink matters twice: it stops absorbing and it can release what it already holds, which is why deforestation and peat drainage appear in climate data.
Reset break
Part 8 of 25
Pause
That's sitting 2 of 6 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Quick check
Part 9 of 25
Quick check
Part 10 of 25
Learning cycle
Part 11 of 25
Learning cycle 2 of 2
Why the balance has shifted
A short piece of teaching, then a check to make sure it has landed.
Reset break
Part 12 of 25
Pause
That's sitting 3 of 6 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Explore the idea
Part 13 of 25
Learn
What human activity added
Burning fossil fuels releases carbon that was locked away for millions of years, adding it to the atmosphere far faster than natural processes remove it. Cement production, intensive agriculture and land-use change add more. Atmospheric carbon dioxide concentration has risen sharply since industrialisation, and the pattern is measured directly at monitoring stations and confirmed in ice cores.
Explore the idea
Part 14 of 25
Learn
Consequences and responses
More greenhouse gas means more energy retained near the surface, raising average global temperature. Consequences include sea level rise from melting ice and thermal expansion, shifting rainfall patterns, ocean acidification and more frequent extreme weather. Responses fall into reducing emissions and increasing sequestration; evaluating them means weighing effectiveness, cost and who is affected.
Quick check
Part 15 of 25
Reset break
Part 16 of 25
Pause
That's sitting 4 of 6 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Quick check
Part 17 of 25
Common mix-ups
Part 18 of 25
Common mix-ups
Things people often get wrong
- People often confuse the greenhouse effect with ozone depletion. They are separate problems with different causes.
- People often think weather disproves climate change. Climate is the long-term pattern, not a single cold week.
Challenge round
Part 19 of 25
Game · Sort it
Which of these are true?
Drag each card into the right column. Tap a card first if dragging is fiddly.
True
Not true
Reset break
Part 20 of 25
Pause
That's sitting 5 of 6 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Challenge round
Part 21 of 25
Game · Fill the gaps
Finish the sentences
Choose the word that belongs in each gap.
Photosynthesis removes ____ dioxide from the air and locks carbon into glucose.
Cold water dissolves carbon ____, and marine organisms build shells that eventually form rock.
Cement ____, intensive agriculture and land-use change add more.
Challenge round
Part 22 of 25
Game · Recall cards
Which process removes carbon dioxide from the air?
Card 1 of 4
Exit quiz
Part 23 of 25
Exit quiz
Show what you've learned
6 questions, marked together at the end. Nothing is timed.
1. Decomposers return carbon to the air through...
2. Peatlands are important because they...
3. Ice cores are useful because they...
4. Ocean acidification is caused by...
5. Which reduces atmospheric carbon dioxide?
6. Climate differs from weather because climate is...
Mastery quiz
Part 24 of 25
Marked quiz
End of lesson quiz: The carbon cycle and climate change
4 questions, marked with the reasoning shown. No timer.
1. Which process removes carbon dioxide from the air?
2. A carbon sink is a store that...
3. Burning fossil fuels matters because it...
4. Sea level rise is caused partly by...
Lesson round-up
Part 25 of 25
Lesson round-up
Ready when you are
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Ask LunaPart 1 of 25 · Watch & discover