The atmosphere does not check passports. A tonne of carbon dioxide released in one country warms every country, which means no government can solve this on its own no matter how good its policies are. That single fact explains why the story of climate action is a story of treaties — and why those treaties are so hard to agree.
📚 What you need to know
Climate change is a global problem, so it needs coordinated international action.
State sovereignty is the principle that a country governs itself without outside interference. Climate treaties ask countries to give up a little of it.
The treaties to know: UNFCCC (1992), Kyoto Protocol (1997), Doha Amendment (2012), Paris Agreement (2015), plus Montreal (1987) and the Kigali Amendment (2016).
Paris works through Nationally Determined Contributions (NDCs), reviewed every five years, aiming for well below 2°C and ideally 1.5°C.
Decarbonisation means cutting fossil fuel use and shifting to renewable energy.
Carbon neutrality (net zero) means emissions released are balanced by an equal amount removed.
Cooperation tools include negotiations, protocols and conventions, and sanctions such as cross-border carbon taxes.
Why one country cannot fix it alone
Imagine a country that decides to cut its emissions to zero tomorrow. It pays the entire cost of that change. The benefit — a slightly cooler planet — is spread across all 190-plus countries, most of which paid nothing. Meanwhile the countries that carried on burning coal still warm the atmosphere that the first country is trying to protect. Acting alone is expensive and barely works.
This is why international cooperation is not just nice to have. It is the only mechanism that can work. But cooperation runs into state sovereignty: the principle that each country has the right to govern itself without external interference. A binding emissions target means accepting rules written partly by other people, and governments guard that power closely. Every climate treaty is a compromise between what the science needs and how much sovereignty countries are willing to trade away.
Montreal is on the timeline because examiners like it as a contrast: it dealt with ozone-depleting substances, it worked, and it shows what a well-designed treaty can achieve.
If you learn nothing else about these treaties, learn this contrast. Kyoto set legally binding targets but only for developed countries, and several large emitters stayed outside it. Paris asks every country to set its own target, which is weaker on paper but got almost everyone signed up. Strict rules with few members, or loose rules with everyone — that tension is worth a mark in almost any evaluation question.
The treaties one by one
Agreement
Year
What it actually did
Montreal Protocol
1987
Phased out CFCs to protect the ozone layer; widely treated as the model of a treaty that worked
UNFCCC
1992
Agreed at the Rio Earth Summit; set up the framework and the annual meetings, but no targets of its own
Kyoto Protocol
1997
First treaty with legally binding emission cuts, required only of developed countries
Doha Amendment
2012
Extended Kyoto to 2013–2020 with new targets and more support for adaptation in developing countries
Paris Agreement
2015
Well below 2°C, aiming for 1.5°C; every country submits an NDC, reviewed and strengthened every five years
Kigali Amendment
2016
Added HFCs to the Montreal Protocol, cutting them 85% by 2047 — a climate fix bolted onto an ozone treaty
Glasgow Pact
2021
Agreed to reduce coal use and methane emissions, and pledged adaptation funding for developing nations
COP28, Dubai
2023
First explicit call to transition away from fossil fuels; tripling renewables by 2030; Loss and Damage Fund formalised
Why HFCs ended up in an ozone treaty. CFCs were replaced by HFCs because HFCs do not damage ozone. Then it turned out HFCs are extremely powerful greenhouse gases. Rather than start a new treaty, countries amended the one that already worked. Kigali could prevent up to 0.5°C of warming on its own.
How countries are made to cooperate
There is no world government to enforce climate policy, so cooperation relies on three softer tools. Negotiations are where countries argue out shared goals, usually at the annual COP meetings. Protocols and conventions turn those goals into formal written commitments. Sanctions add pressure, and the one to know is the cross-border carbon tax.
A cross-border carbon tax is a charge on imported goods based on the emissions produced while making them. If steel made in a country with weak climate rules is taxed when it enters a country with strong ones, the price advantage of polluting disappears. This tackles carbon leakage, which is what happens when a country’s emissions appear to fall simply because its dirty industries relocated somewhere with looser rules. The emissions did not go away; they just moved off that country’s balance sheet.
Decarbonisation and net zero
Decarbonisation means reducing or ending the use of fossil fuels — coal, oil and natural gas — and replacing them with renewable sources such as solar, wind, hydro and geothermal. Carbon neutrality, usually called net zero, is the point where the carbon dioxide a country releases is balanced by an equal amount removed from the atmosphere.
Cement, steel, aviation and some farming emissions are extremely hard to remove entirely, which is why net zero targets rely on carbon sinks and capture technology to cancel out that final slice.
The four routes to decarbonising
Renewable energy. Replace coal and gas power stations with solar, wind, hydro and geothermal.
Energy efficiency. Waste less in the first place — insulation, efficient lighting, better appliances, smarter industrial processes.
Electrification. Move heating, cooking and transport from burning fuel directly to running on electricity, which only helps if that electricity is clean.
Carbon capture and storage (CCS). Capture carbon dioxide at the source, compress and transport it, then inject it deep underground for long-term storage.
Targets to quote. The UK and the EU aim for net zero by 2050, Germany by 2045 and China by 2060. These dates form part of each country’s NDC under the Paris Agreement, so they are promises made internationally, not just domestic policy.
Two examples worth memorising
The EU Green Deal
The European Union aims to be the first climate-neutral continent by 2050. Three of its policies are worth naming. The carbon border adjustment mechanism taxes imports according to their emissions, which prevents carbon leakage and stops EU industries being undercut by competitors with weaker rules. Renewable energy expansion sets targets for the share of renewables in the energy mix. Energy efficiency measures push efficient technology across every sector.
Norway
Norway generates close to all of its electricity from renewable sources, mostly hydropower, and has pushed electric vehicles hard through tax exemptions, toll reductions and free parking. It set out to end sales of new fossil fuel cars by 2025. There is a useful complication here: Norway is also a major oil and gas exporter, so its domestic emissions look excellent while the fuel it sells is burned elsewhere. Mentioning that tension shows real understanding.
WORKED EXAMPLE
Explain why international cooperation is necessary to address climate change. [4]
Point 1 — the atmosphere is sharedGreenhouse gases mix throughout the atmosphere, so emissions released anywhere affect the climate everywhere.Point 2 — acting alone does not workOne country cutting emissions pays the full cost but gains only a small share of the benefit, so unilateral action has limited effect.Point 3 — the leakage problemWithout shared rules, high-emitting industries relocate to countries with weaker regulations, so global emissions do not fall.Point 4 — named mechanismTreaties such as the Paris Agreement create shared targets and review processes that hold countries accountable to each other.4 / 4Naming a treaty in the final point turns a general answer into a specific one.
WORKED EXAMPLE
Distinguish between decarbonisation and carbon neutrality. [2]
Mark 1 — decarbonisationDecarbonisation is the process of reducing or ending fossil fuel use and switching to low-carbon energy sources.Mark 2 — carbon neutralityCarbon neutrality is the end state where remaining emissions are balanced by an equal quantity of carbon dioxide removal, giving net zero.2 / 2One is the journey, the other is the destination. Say that and the mark is safe.
💡 Exam tip
Learn treaty plus year plus one achievement. Three facts each is enough and it beats vague references to “international agreements”.
Use the Kyoto versus Paris contrast whenever a question asks you to evaluate global action.
Define state sovereignty explicitly if the question mentions it. It is a definition mark sitting in plain sight.
Keep EU Green Deal and Norway as your two ready examples, and add the Norwegian oil export tension for extra credit.
Explain carbon leakage whenever you mention a cross-border carbon tax — the tax only makes sense once leakage is defined.
Remember net zero is a balance. Saying it means “no emissions at all” loses the mark.
⚠️ Common mix-up
Confusing the UNFCCC with the IPCC. The UNFCCC is the negotiating body; the IPCC assesses the science and writes the reports.
Saying Paris is legally binding. Countries must submit and report an NDC, but the targets inside it are self-set and not enforced.
Thinking the Montreal Protocol was about climate change. It was about ozone. Kigali is the amendment that made it a climate treaty too.
Treating net zero as zero emissions. It is emissions minus removals equalling zero.
Assuming electrification is automatically clean. An electric car charged from a coal grid still carries emissions.
Forgetting COP means Conference of the Parties — the annual meeting of UNFCCC members, not an organisation in itself.
Up next: Mitigating Climate Change — moving from what countries have promised to the actual strategies that cut emissions at source and pull carbon back out of the air.
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