Mitigation means attacking the cause: fewer greenhouse gases going up, and more coming back down. There are a lot of strategies to learn, but they sort into a simple order of preference — and knowing that order is what turns a list into an evaluation.
📚 What you need to know
Mitigation means reducing and stabilising greenhouse gas emissions — cutting them at source, and removing gases already in the atmosphere.
Reduce emissions through: lower energy consumption, transport policy, cleaner agriculture, and alternatives to fossil fuels.
Remove or offset through: natural carbon sinks (afforestation, reforestation, rewilding) and carbon capture and storage, including direct air capture.
A carbon tax puts a price on emitting, so cutting emissions becomes the cheaper choice.
Geoengineering — such as stratospheric aerosol injection to reflect sunlight — is a last-resort idea with serious unknowns.
Afforestation is planting where there was no forest; reforestation is replanting where forest was lost.
Not all mitigation is equal
The strategies below are not interchangeable. Some are cheap, proven and available now; others are expensive, unproven or carry risks of their own. Sorting them into an order of preference is the single most useful thing you can do with this topic, because “evaluate” questions are asking exactly that.
This ordering is not in the syllabus as a diagram, but it is how mark schemes reward judgement: prevention first, technology last.
The strategies in full
Strategy
How it is put into practice
Reducing energy consumption
Insulation, efficient lighting and appliances, smart grids and energy management systems, and more efficient industrial processes
Transport policy
Fuel efficiency standards, support for electric and hybrid vehicles, investment in public transport, and making cycling and walking practical choices
Cleaner agriculture
Practices that cut methane and nitrous oxide: better feed quality, methane capture on farms, rotational grazing, and careful use of nitrogen fertiliser
Alternatives to fossil fuels
Solar, wind, hydro and geothermal generation; electric vehicles and charging networks; research into biofuels, hydrogen and nuclear
Carbon tax
A charge per tonne of carbon dioxide emitted, so that polluting costs money and cleaner options become the cheaper business decision
Natural carbon sinks
Afforestation and reforestation, rewilding, restoring degraded ecosystems, and protecting the forests that already exist
Carbon capture and storage
Capturing carbon dioxide from power stations and industry, or straight from the air by direct air capture, then storing it underground long term
Geoengineering
Deliberate large-scale intervention in the climate, such as injecting aerosols into the stratosphere to reflect sunlight back into space
Two words examiners separateafforestation = planting trees where there was no forest reforestation = replanting where forest has been cleared or degraded
Protecting an existing old forest usually beats planting a new one. Mature woodland already stores enormous amounts of carbon, and a sapling takes decades to lock away what a felled tree releases in an afternoon.
How carbon capture and storage works
The cap rock matters: carbon dioxide is injected below a layer of impermeable rock that stops it rising back to the surface.
The honest limitation: capturing carbon dioxide takes energy, which means a plant with CCS burns more fuel to produce the same electricity. It is worth doing where emissions are otherwise unavoidable — not as a reason to keep building fossil-fuelled plants.
Carbon taxes: making pollution cost something
Emitting carbon dioxide is normally free to the emitter, while the damage is paid for by everyone else, often decades later. A carbon tax fixes that mismatch by attaching a price per tonne. Suddenly the efficient boiler, the electric van and the renewable contract are not just greener, they are cheaper — so businesses switch for ordinary financial reasons rather than moral ones.
The weaknesses are equally clear. Energy costs rise, and that hits low-income households hardest unless the revenue is returned to them. Industries may relocate to countries without a tax, which is the carbon leakage problem that cross-border carbon taxes are designed to close.
Geoengineering: the last resort
Stratospheric aerosol injection would spray reflective particles high into the atmosphere to bounce a fraction of incoming sunlight back into space, imitating what a large volcanic eruption does naturally. It would probably cool the planet, and it would be relatively cheap.
The problems are serious. It treats the symptom while carbon dioxide keeps accumulating, so ocean acidification continues untouched. It would change rainfall patterns unevenly, creating winners and losers with no agreed way to decide between them. Stopping suddenly would cause very rapid warming. And the mere promise of it can reduce the pressure to cut emissions now.
If you mention geoengineering in an answer, always place it as a last resort and name one specific risk. Presenting it as a solution loses the judgement marks.
Worked examples
WORKED EXAMPLE
Evaluate the use of a carbon tax as a climate change mitigation strategy. [4]
How it works
A charge per tonne of carbon dioxide emitted makes polluting expensive, so cleaner technology becomes the cheaper option.
Strengths
Acts across the whole economy at once, raises revenue that can fund renewables or support households, and lets businesses choose their own cheapest route to cutting.
Weaknesses
Raises energy prices, which hits poorer households hardest; industries may move abroad, causing carbon leakage; and the rate has to be high enough to change behaviour.
JudgementEffective when set at a meaningful level and paired with a border adjustment and support for low-income households.Powerful, but only with the right design
WORKED EXAMPLE
Compare reforestation with carbon capture and storage as ways of removing carbon dioxide. [4]
Reforestation
Cheap, low technology and brings extra benefits — habitat, biodiversity, soil protection and flood control.
But it is slow, needs a lot of land that may be wanted for food, and the carbon can be released again by fire, disease or felling.Carbon capture and storage
Locks carbon away for centuries, works at industrial scale, and takes very little land.
But it is expensive, consumes energy, is not yet deployed widely, and depends on the storage site staying sealed.Judgement
Forests are better value now; CCS suits emissions that cannot be avoided any other way.
Different tools for different emissions
💡 Exam tip
Split mitigation into reduce at source and remove from the atmosphere. It structures any answer instantly.
Know the difference between afforestation and reforestation — it is a definition mark waiting to be taken.
For “evaluate”, weigh cost, speed, scale, land needed, permanence and side effects. Six angles, pick the two or three that fit.
Name a real policy: carbon taxes, EV incentives, EU renewable targets. Specific beats general every time.
Place geoengineering last and give a risk. Judgement earns the top band.
⚠ Common mix-up
Mitigation is not adaptation. Mitigation tackles the cause; adaptation copes with the effects.
Planting trees does not cancel out emissions immediately. The carbon takes decades to accumulate, and it can be released again.
CCS is not carbon-free. Capturing and compressing the gas uses energy of its own.
Electric vehicles are not automatically clean. Their benefit depends on how the electricity was generated and how the batteries were made.
Geoengineering does not fix ocean acidification. Reflecting sunlight does nothing about carbon dioxide dissolving into the sea.
Nuclear is not renewable. It is low-carbon, which is a different claim — use the right word.
Up next: Adapting to a Changing Climate — flood defences, drought-resistant crops, adaptation plans, and why the countries needing them most are rarely the ones that caused the problem.
Want this explained one-to-one?
Book a free session with an experienced IB ESS tutor and get your trickiest topics made simple.
