Mitigation at Higher Level: The same three categories as SL, with different real cases: Vietnam's mangroves, the Great Barrier Reef cloud-brightening trial, Denmark's livestock tax, Orca in Iceland and New Zealand's plan. At HL, judge strategies through economics and values: who pays, and which worldview each strategy reflects.
Practise this as you read
- Give two examples from each category.
- Test the claim that mitigation is ecocentric and adaptation technocentric.
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Treat the cause, or live with the effects: Mitigation tackles the cause; adaptation copes with the effects.
The points to remember
- Mitigation reduces the cause of climate change: it cuts greenhouse gases or removes CO2 from the air.
- Adaptation reduces the negative impacts, or makes the most of the positive ones: it deals with effects.
- Mitigation benefits everyone and needs global cooperation; adaptation mostly helps one place.
- Both are needed: some warming is already locked in.
- A strategy can do both, e.g. a green roof cools a building (adaptation) and cuts energy use (mitigation).
Remember it as: Mitigation fixes the cause; adaptation copes with the effects.
Real example: in northern Vietnam, villagers have planted thousands of hectares of mangroves in front of the sea dykes since 1994. The trees store carbon in their mud (mitigation) and slow storm waves before they reach the dykes (adaptation).
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The first category does not cut greenhouse gases at all. It changes how much of the Sun's energy the Earth keeps.
Category 1: slowing the warming process
- Category 1 reduces the process of warming: less of the Sun's energy is kept.
- Household changes: pale or 'cool' roofs and walls reflect sunlight, so buildings need less cooling.
- Geoengineering: deliberate, large-scale changes to the climate system.
- e.g. spraying aerosols into the stratosphere, or brightening clouds so they reflect more sunlight.
- Risks: CO2 keeps rising, so ocean acidification goes on; side effects on rain are unknown.
- If it stopped suddenly, the hidden warming would return fast (termination shock).
Geoengineering: for
- Could cool the Earth quickly
- Cheap compared with cutting emissions
- Buys time
Geoengineering: against
- CO2 and acidification continue
- Unknown effects on rain
- Who controls the planet's thermostat?
Real example: in March 2020 scientists sprayed tiny drops of seawater into the air over the Great Barrier Reef, the first outdoor trial of marine cloud brightening. The aim is whiter clouds that reflect sunlight and cool the water during heatwaves that bleach coral.
Name the category: When asked for strategies from different categories, say which category each belongs to and how it works: reflect sunlight, cut emissions, or remove carbon dioxide.
Make less of the gas: Most mitigation stops greenhouse gases being made in the first place: in power stations, cars, homes, factories and farms.
Category 2: producing fewer greenhouse gases
- Category 2 reduces the production of greenhouse gases at the source.
- Energy efficiency: insulation, LED lights and efficient machines use less fuel.
- Renewable energy (and low-carbon nuclear, despite its waste, safety and cost issues).
- Food choice: less beef and dairy means less methane and less forest cleared.
- Farming changes: less fertiliser (nitrous oxide), better livestock feed, wetting and drying rice.
- Carbon tax: a price per tonne of CO2 makes fossil fuels dearer, so people and firms cut use.
- Also: public transport, cycling, electric vehicles, recycling and fuel switching in industry.
Real example: in 2024 Denmark agreed the world's first tax on the greenhouse gases from farm animals. From 2030, farmers will pay 300 kroner per tonne of CO2 equivalent from cattle and pigs, rising to 750 kroner in 2035, with a 60% allowance that lowers the real rate.
Percentage reduction: % reduction = (fall ÷ original) × 100. A coal plant releasing 900 tonnes of CO2 a day is replaced by a wind farm releasing 90: fall = 810, so (810 ÷ 900) × 100 = 90%.
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The third category takes carbon dioxide back out of the air, by nature or by machine.
Category 3: removing carbon dioxide
- Category 3 removes CO2 already in the atmosphere.
- Carbon sinks: forests, soils, peat bogs, mangroves, seagrass and kelp absorb CO2 by photosynthesis.
- Afforestation (new forest) and reforestation (replanting cleared land).
- Rewilding: restore species and habitats, e.g. more sea otters eat urchins, so kelp regrows and absorbs more CO2.
- Carbon capture and storage (CCS): trap CO2 at a power station or gas field and pump it underground.
- Direct air capture: machines filter CO2 out of the air (very expensive, small so far).
Reading the graph: Read the bars side by side: per hectare, mangroves store about three times as much carbon as rainforest, mostly in waterlogged soil where it does not rot. But rainforests cover a far larger area of the world, so in total they hold much more.
Real example: the Orca plant in Iceland, opened in 2021, uses fans to pull up to 4,000 tonnes of carbon dioxide a year out of the air. The company Carbfix pumps it into basalt rock, where it turns to stone within about two years.
Judge a strategy, do not just describe it: Papers ask you to evaluate one strategy, often reforestation. Give points on both sides, then a judgement.
Reforestation: strengths
- Absorbs CO2 by photosynthesis
- Increases biodiversity
- Little technology or cost
- A renewable sink that lasts
- Holds soil: less erosion
- More cloud may raise albedo
Reforestation: limitations
- Darker trees absorb more heat
- More water vapour (a GHG)
- Takes farmland or building land
- Needs very large areas
- Slow: decades to grow
- Can burn, releasing the carbon
Five tests for any strategy
- Effectiveness: how much CO2 does it cut or remove, and for how long?
- Cost: who pays, and can poorer countries afford it?
- Feasibility: is the technology ready, is there land, will people accept it?
- Time scale: trees take decades; a carbon tax works as soon as prices change.
- Side effects: jobs, health, wildlife, water, food prices.
Real example: in 2023 wildfires in Canada burned over 15 million hectares of forest and released more carbon dioxide than most countries emit in a year: a planted forest is a store that can be lost.
Too vague to count: 'Trees improve air quality' or 'reduce pollution' do not count: link every point to carbon dioxide, heat, land or time.
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Which strategies a society chooses depends on its values, and a real country's plan is usually a mix that works in some sectors and not in others.
Strategies and value systems
- Ecocentric mitigation: use less energy, eat less meat, protect forests, small local renewables.
- Technocentric mitigation: CCS, geoengineering, nuclear power, ocean fertilisation.
- Technocentric adaptation: sea walls, desalination, vaccines; ecocentric: mangroves, local crops.
- Anthropocentric tools: carbon taxes, emissions trading, laws, international agreements.
- So 'mitigation is ecocentric, adaptation technocentric' is only partly true.
Test the claim both ways: In an essay on values, find the exceptions: technocentric mitigation (CCS) and ecocentric adaptation (mangroves) show the claim is only partly true.
Limiting the harm without burning less fossil fuel
- Capture CO2 (CCS) or plant trees to absorb it.
- Clean exhausts: scrubbers on power stations, catalytic converters on cars, low-sulphur coal.
- Repair damage, e.g. add lime to acidified lakes.
- Adapt to the effects: sea defences, vaccination, masks.
- Not efficiency: it works by burning less, which the question rules out.
Real example: New Zealand plans all-renewable electricity and an emissions trading scheme, but electricity makes only about 6% of its greenhouse gases. Agriculture, mainly methane from about 10 million cattle, makes about half, and farm emissions are not yet priced.
How this comes up: Paper 2, Section B (c): a 9-mark essay that links strategies to value systems.
A newspaper writes: 'Cutting emissions is what nature lovers want; building sea walls is what engineers want.'
In addressing global warming, mitigation strategies may be seen as primarily ecocentric and adaptation strategies as primarily technocentric. To what extent is this view valid, with reference to named strategies?
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