The big idea: Mitigation means reducing the cause of climate change — cutting how much greenhouse gas (mainly CO₂ and methane) humans add to the atmosphere.
The opposite is adaptation, which means coping with the effects that are already happening.
Mitigation works in two main ways: add less CO₂ (burn fewer fossil fuels) and remove more CO₂ (protect the natural carbon sinks that soak it up).
Mitigation = rebalance the two arrows. The UP arrow (combustion of fossil fuels) is the human add-on raising CO₂; the DOWN arrow (photosynthesis) removes it. Cut the up-arrow or protect the down-arrow and atmospheric CO₂ stops rising.
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- Mitigation
- Action that reduces the cause of climate change — lowering greenhouse-gas emissions or removing greenhouse gases from the atmosphere.
- Adaptation
- Action that copes with the effects of climate change that are already happening (e.g. sea walls, drought-tolerant crops).
- Carbon sink
- A store that removes more CO₂ from the air than it releases — forests, peatlands, soils and the oceans.
- Carbon sequestration
- The removal and long-term storage of CO₂ from the atmosphere, mainly by photosynthesis into plants and soils.
- Renewable energy
- Energy from sources that are not used up and do not burn carbon — solar, wind, hydroelectric, geothermal.
Two levers, one goal: Look at the carbon cycle as two arrows.
The up-arrow = processes that add CO₂ (combustion of fossil fuels is the human add-on).
The down-arrow = photosynthesis, which removes CO₂.
Every mitigation strategy either shrinks the up-arrow (emit less) or protects the down-arrow (keep the sinks working). Keep that picture and any strategy makes sense.
An exam answer on mitigation must do more than name a strategy — it must explain the mechanism: how the action changes the amount of CO₂ in the air.
Read each one as a chain of cause and effect, ending at 'so atmospheric CO₂ falls (or stops rising)'.
| Mitigation strategy | What it does | How it lowers atmospheric CO₂ |
|---|---|---|
| Reduce fossil-fuel combustion | Replace coal, oil and gas with renewables (solar, wind, hydro) and use energy more efficiently | Less carbon is burned, so the 'combustion' up-arrow that adds CO₂ to the air shrinks |
| Protect and restore carbon sinks | Stop deforestation; replant forests; protect peatlands, wetlands and oceans | Photosynthesis keeps removing CO₂ (the down-arrow); stored carbon is not released by burning or decay |
| Reduce other greenhouse-gas sources | Cut methane from cattle and landfill; change farming and diets | Fewer molecules that absorb longwave infrared, so less heat is trapped |
| Capture and store carbon | Carbon capture and storage (CCS) traps CO₂ from emissions and locks it underground | CO₂ is removed from the flow before it reaches the atmosphere |
The mechanisms, spelled out
- Switch to renewables. Solar, wind and hydro generate energy without burning carbon, so the combustion up-arrow that releases CO₂ shrinks.
- Use energy more efficiently. Better insulation, public transport and efficient appliances mean less fuel is burned for the same result.
- Stop deforestation / replant forests. Living trees keep removing CO₂ by photosynthesis (sequestration), and unburnt trees keep their carbon locked in wood instead of releasing it.
- Protect peatlands and oceans. These are huge natural sinks; draining or warming them releases stored carbon, so keeping them intact keeps the down-arrow strong.
- Cut methane (CH₄). Fewer cattle, better landfill management and changed diets reduce a powerful greenhouse gas, so less longwave infrared is trapped.
- Carbon capture and storage (CCS). CO₂ is trapped at the source and pumped underground, removing it from the flow before it reaches the atmosphere.
Why protecting sinks is double-edged: A forest is a carbon sink in two ways, so destroying it hurts twice.
Cutting it down removes the down-arrow — those trees stop photosynthesising, so less CO₂ is removed from the air.
Burning or rotting the wood adds an up-arrow — the carbon stored in the trees is released back as CO₂.
So 'protect carbon sinks' both keeps removal going and prevents a new release — that is why it is one of the strongest mitigation levers.
Protecting carbon sinks works on the DOWN arrow: forests, peatlands and oceans pull CO₂ out of the air by photosynthesis. Destroying them (deforestation) weakens the down-arrow AND releases stored carbon up.
Interactive diagram
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Mitigation vs adaptation — don't mix them up: The examiner often checks you can tell these apart.
Mitigation attacks the cause — it lowers CO₂ (e.g. renewables, reforestation).
Adaptation manages the effect — it does not lower CO₂ (e.g. building sea walls, switching to drought-tolerant crops, moving species to cooler ranges).
If an action reduces emissions or removes CO₂, it is mitigation. If it just helps us live with the warming, it is adaptation.
| Mitigation | Adaptation | |
|---|---|---|
| What it targets | The CAUSE — the amount of greenhouse gas added | The EFFECT — coping with warming that is already happening |
| Goal | Slow or stop further warming | Reduce the harm warming does to people and ecosystems |
| Examples | Renewable energy; reforestation; cutting methane | Sea walls; drought-tolerant crops; moving species to cooler ranges |
| Effect on CO₂ | Lowers (or stops the rise in) atmospheric CO₂ | Does NOT lower CO₂ — it just manages the consequences |
See how examiners mark answers
Access past paper questions with model answers. Learn exactly what earns marks and what doesn't.
How this is tested: D4.3 climate questions reward a mechanism, not a list of buzzwords.
On Paper 2 an Explain or Suggest item asks how a strategy reduces CO₂ — you must trace action → effect on the carbon cycle → CO₂ falls.
On Paper 1 a 1-mark item often asks you to identify an action that protects (or harms) a carbon sink, or to tell mitigation apart from adaptation.
Always finish the chain at the atmosphere: '...so less CO₂ is added / more CO₂ is removed.'
IB-style question — explain how reforestation mitigates climate change
A government plans to plant large areas of new forest. Explain how reforestation could help mitigate climate change. [3]
How to score all three marks
- Start with the process. Growing trees carry out photosynthesis, which removes CO₂ from the atmosphere (carbon sequestration).
- Show where the carbon goes. The carbon is fixed and stored in the wood and soil (biomass), so it is locked out of the air for the life of the forest.
- Link to the atmosphere. Because more CO₂ is removed than before, atmospheric CO₂ rises more slowly (or falls), so the greenhouse effect is reduced and warming slows. (1 mark for each distinct linked point, max 3.)
Final answer
Trees photosynthesise and remove CO₂ from the air (sequestration); the carbon is stored in the wood/soil so it is locked out of the atmosphere; this lowers (or slows the rise in) atmospheric CO₂, reducing the greenhouse effect.
✓ Why this scores full marks: It is a chain, not a list: photosynthesis removes CO₂ → carbon stored in wood → atmospheric CO₂ falls.
A weak answer just writes 'trees are good for the environment' — no mechanism, no marks. Always end at the atmosphere.