Carbon dioxide does not stop at a border. A country can cut its emissions to zero and still be flooded by everyone else’s. That is the whole reason climate policy is done through treaties — and the reason those treaties are so hard to agree on.
📚 What you need to know
Climate change is a global problem, so action by individual countries alone is not enough — international cooperation is essential.
State sovereignty is the principle that each country governs itself. Climate agreements ask countries to give up some of it, which is why progress is slow.
The four agreements to know: UNFCCC (1992), Kyoto Protocol (1997), Doha Amendment (2012) and the Paris Agreement (2015).
Paris aims to hold warming well below 2 °C, with efforts towards 1.5 °C, through Nationally Determined Contributions (NDCs) reviewed every five years.
Decarbonisation means moving off fossil fuels and onto renewables. Carbon neutrality (net zero) means emissions are balanced by an equal amount of removal.
Steps: renewable energy, energy efficiency, electrification, and carbon capture and storage (CCS).
Why one country cannot solve it
The atmosphere is shared. Emissions released anywhere mix through the whole system within a year or two, so the benefit of a cut is spread across every country while the cost falls entirely on the one that made it. That is a difficult deal to sell politically, and it is exactly why cooperation has to be negotiated rather than assumed.
State sovereignty makes it harder still. Every country has the right to govern itself without outside interference, so no international body can simply order a nation to close its coal plants. Agreements therefore work by persuasion, commitment and compromise: countries voluntarily accept limits on their own freedom because the alternative is worse for everyone, including them.
If an exam question asks why global agreements are difficult, sovereignty is the answer they want. Add that the countries emitting most historically are not the ones suffering most, and you have the fairness argument too.
The four agreements
Learn the four dates and one distinguishing feature of each. That is usually all a question needs.
Agreement
What it did
UNFCCC, 1992
Established at the Earth Summit in Rio de Janeiro. Set up the framework for all later international climate work, and encouraged developed countries to lead on cutting emissions and to support developing ones
Kyoto Protocol, 1997
The first major treaty actually aimed at reducing greenhouse gases, setting legally binding reduction targets for developed countries
Doha Amendment, 2012
Extended Kyoto beyond its original end date, setting new targets for developed countries for 2013–2020 and encouraging support for adaptation in developing countries
Paris Agreement, 2015
Aims to hold warming well below 2 °C above pre-industrial levels, with efforts towards 1.5 °C. Nearly all countries committed. Each submits an NDC setting out its own plan, reviewed and strengthened every five years
The key difference: Kyoto imposed targets from above on a small group of countries. Paris lets each country set its own target, but gets almost everyone involved and reviews progress regularly. Broader participation, weaker enforcement.
How cooperation is actually made to work
Negotiations — countries meet to agree common goals, commitments and actions.
Protocols and conventions — formal agreements setting out exactly what each country has committed to do.
Sanctions — measures that make non-compliance costly. The clearest example is a cross-border carbon tax: a charge on imported goods based on the emissions produced while making them.
Cross-border carbon taxes exist to solve a specific problem. If one country puts a strict price on carbon, its factories become more expensive to run, and production can simply move abroad to somewhere with weaker rules. The emissions do not fall — they relocate. This is called carbon leakage. Taxing imports on their embedded carbon evens out the cost, protects industries that are following the stricter rules, and pushes exporters everywhere to clean up.
Decarbonisation and net zero
Decarbonisation means reducing or ending the use of coal, oil and natural gas, and replacing them with renewable sources such as solar, wind, hydro and geothermal energy.
Definition to learn
carbon neutrality (net zero) = emissions released balanced by an equal amount of carbon dioxide removed
Removal is meant for the emissions that are genuinely hard to eliminate, such as cement, steel and aviation — not as a substitute for cutting the easy ones.
Targets countries have set
Germany — carbon neutral by 2045.
United Kingdom — net zero by 2050.
China — carbon neutral by 2060.
These dates are not arbitrary promises. Each forms part of that country’s NDC under the Paris Agreement, which is what makes them reviewable.
The four steps to getting there
🧩 How an economy decarbonises
Switch to renewable energy — solar, wind, hydro and geothermal replacing fossil-fuelled generation.
Improve energy efficiency — insulation, efficient lighting and appliances, smart grids, and less waste in industry and transport. The cleanest unit of energy is the one never used.
Electrify — move heating, cooking and transport from burning fuel to electricity, so that as the grid gets cleaner, everything connected to it does too.
Capture and store what is left — CCS captures carbon dioxide at power plants and industrial sites, compresses and pipes it to a storage site, and injects it deep underground.
Two examples worth learning
The EU Green Deal
Aims to make Europe the first climate-neutral continent by 2050.
Includes a carbon border adjustment mechanism — a carbon charge on imports, designed to stop carbon leakage and keep competition fair for EU industries facing strict rules at home.
Sets targets to expand renewables in the energy mix and promotes energy-efficient technology across sectors.
Norway
Generates close to 100% of its electricity from renewables, mostly hydropower.
Pushed electric vehicles hard using incentives rather than bans: tax exemptions, reduced tolls and free parking.
Has policy aimed at phasing out sales of new fossil-fuelled vehicles, cutting transport emissions directly.
Norway is a genuinely useful example because it shows incentives working — but a strong answer also notes that Norway remains a major oil and gas exporter. Emissions counted at home are not the same as emissions caused.
Worked examples
WORKED EXAMPLE
Explain why international cooperation is necessary to address climate change, and why it is difficult to achieve. [4]
Why it is necessary
Greenhouse gases mix through the whole atmosphere, so emissions anywhere warm everywhere. One country acting alone cannot protect itself.
The shared-cost problem
The cost of cutting emissions falls on one country while the benefit is shared globally, so there is little incentive to act first.
Why it is difficult
State sovereignty means no country can be forced to comply, so agreements rely on voluntary commitment and compromise.
The fairness disputeDeveloped countries emitted most historically, while developing countries face the worst impacts and want the same chance to grow — so who cuts, and by how much, is contested.Shared atmosphere, separate governments
WORKED EXAMPLE
Explain how a cross-border carbon tax works and evaluate its usefulness. [4]
How it works
Imported goods are charged according to the emissions produced while making them, so foreign and domestic producers face a similar carbon cost.
The problem it solves
Without it, strict rules in one country push production abroad and the emissions simply move — carbon leakage.
Strengths
Protects industries that are decarbonising, and gives exporters worldwide a financial reason to cut emissions.
WeaknessesHard to measure embedded carbon accurately, can be seen as a trade barrier by developing countries, and may raise consumer prices.Effective in principle, contested in practice
💡 Exam tip
Learn the four agreements with dates. 1992, 1997, 2012, 2015 — and one feature each.
Quote the Paris targets exactly: well below 2 °C, with efforts towards 1.5 °C.
Use the word sovereignty when explaining why agreements are weak. It is the concept being tested.
Have one named example ready, such as the EU Green Deal or Norway’s EV incentives. Examiners reward current, specific detail.
Explain net zero as a balance between emissions and removals, not as zero emissions.
⚠ Common mix-up
Net zero is not zero emissions. Some emissions continue and are offset by removals.
The UNFCCC is not a treaty with targets. It set up the framework; Kyoto and Paris carry the commitments.
Paris targets are not legally enforced. Countries set their own NDCs, and the mechanism is review and pressure, not punishment.
Decarbonisation is not only about electricity. Heating, transport, farming and industry all have to change too.
Carbon leakage is not the same as an emissions cut. Moving a factory abroad lowers one country’s figures and changes nothing globally.
Up next: Mitigating Climate Change — the full set of strategies for cutting and removing greenhouse gases, and how to rank them for marks.
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