Why climate change needs policy
Burning coal, oil and gas, cutting forests and some farming release greenhouse gases such as carbon dioxide (CO₂) and methane. They trap heat, and the planet has already warmed by about 1.1–1.2 °C since the 1800s. How much it warms depends on the total CO₂ we add, so scientists talk about a carbon budget: the amount we can still emit before passing a temperature limit.
The atmosphere is a shared resource. A factory's smoke harms people far away who did not choose it; economists call this an externality. Because no one pays for that harm, the market alone produces too much pollution. That is why governments make climate policy.
- Mitigation: cutting emissions or removing CO₂ (clean energy, efficiency, forests).
- Adaptation: preparing for changes already coming (sea walls, drought-proof crops, heat warnings).
Development and emissions are linked: as countries industrialise, emissions usually rise. The challenge is to grow incomes while emissions fall, which some countries have begun to do (called decoupling).
International cooperation: UNFCCC, Kyoto and Paris
- 1992 UNFCCC (agreed at the Earth Summit in Rio): almost every country joined a framework to stop "dangerous" interference with the climate. Countries meet every year at a COP (Conference of the Parties). The IPCC gives them the science.
- 1997 Kyoto Protocol: legally binding targets, but only for developed countries. It created carbon markets, but some big emitters did not take part, and developing countries had no targets.
- 2015 Paris Agreement: every country takes part. The goal is to hold warming well below 2 °C and try for 1.5 °C, and to reach net zero in the second half of the century. Each country writes its own Nationally Determined Contribution (NDC) and must update it every five years with more ambition (the "ratchet"). A global stocktake checks progress.
Other cooperation mechanisms: climate finance (for example the Green Climate Fund), technology transfer, carbon credit trading between countries, regional energy and transport links, and agreements on single gases (the Montreal Protocol and its Kigali amendment cut gases that also warm the planet). Large regional infrastructure programmes, such as cross-border transport and energy corridors, can either lock in high emissions or speed up clean energy, depending on whether they build coal plants or solar and rail.
National policy tools
- Carbon tax: a fixed price on each tonne of CO₂. Polluters pay, so clean options become cheaper by comparison. The price is certain; the amount of cut is not.
- Cap-and-trade (emissions trading): the government sets a cap on total emissions and hands out or sells permits. Firms that cut cheaply can sell spare permits. The amount of emissions is certain; the price is not.
- Rules and standards: fuel-efficiency standards for cars, building codes, phasing out coal plants, banning certain gases.
- Support and investment: subsidies or auctions for solar and wind, public transport, electric vehicles, research, and planting forests.
- Information: energy labels, awareness campaigns.
Many countries publish targets with dates: for example a cut of a certain percentage by 2030 and net zero by 2050, 2060 or 2070. Good targets are backed by laws, sector plans (power, industry, transport, buildings, farming) and yearly reporting.
Net zero and carbon neutrality
Net zero (for CO₂, also called carbon neutrality) means that the greenhouse gas still released is balanced by the amount removed from the air, so the total added each year is zero.
Net emissions = emissions − removals.
Ways to get there: first cut emissions as deeply as possible (clean electricity, electric transport, efficient buildings, cleaner industry, less food waste). Then balance what is left with removals: growing forests, restoring wetlands and soils, and technologies such as carbon capture and storage. Removals are limited and slow, so they cannot replace cutting.
Example targets announced by governments: the EU, the UK, Korea and Japan for 2050, China for 2060 and India for 2070. Because warming depends on the total pile of CO₂, reaching net zero sooner keeps warming lower.
Fairness and equity in climate action
Who should cut first and pay most? Countries see this differently.
- Historical responsibility: industrialised countries have released the largest share of all CO₂ since 1850.
- Per person emissions: an average person in a high-income country emits many times more than one in a low-income country.
- Right to develop: poorer countries need energy to end poverty.
- Vulnerability: those who emitted least, such as small islands and poor farming regions, often suffer most from floods, droughts and heat.
The UNFCCC principle of common but differentiated responsibilities and respective capabilities (CBDR-RC) means every country must act, but richer ones should lead and help others with climate finance (rich countries promised to mobilise 100 billion US dollars a year, and later agreed a larger goal), technology transfer and a loss and damage fund for harm that cannot be avoided. A just transition also protects workers and communities that depend on coal or oil.
Key formulas and definitions
- [object Object]
- [object Object]
- [object Object]
- [object Object]
- [object Object]
- [object Object]
Worked examples
1. A country emits 400 million tonnes of CO₂ a year and its forests absorb 60 million tonnes. What are its net emissions, and how far is it from net zero?
Net = 400 − 60 = 340 million tonnes. It must cut emissions and/or add removals by 340 million tonnes to reach net zero.
2. A carbon tax of $40 per tonne applies to a factory that emits 25,000 tonnes a year. What does it pay? What happens if it cuts emissions by 10,000 tonnes?
25,000 × 40 = $1,000,000. After cutting, it pays 15,000 × 40 = $600,000, saving $400,000, so it has a reason to cut whenever cutting costs less than $40 a tonne.
3. Why was the Paris Agreement able to include almost every country when Kyoto did not?
Kyoto set binding targets only for developed countries, so some emitters stayed out and developing countries had none. Paris lets each country choose its own NDC, so everyone can join, then uses five-yearly updates and public reporting to push ambition up.
4. Country A emits 15 t of CO₂ per person with 50 million people; country B emits 2 t per person with 500 million people. Which emits more in total, and what does this show about fairness?
A: 15 × 50 million = 750 million t. B: 2 × 500 million = 1,000 million t. B emits more in total, but each person in A emits 7.5 times more. Totals and per-person figures tell different fairness stories.
Common mistakes
- Thinking net zero means zero emissions. It means emissions left over are balanced by removals.
- Mixing up mitigation and adaptation. Mitigation cuts the cause; adaptation copes with the effects.
- Saying the Paris Agreement sets each country's target. Each country chooses its own NDC; the agreement sets the shared goal and the rules for updating and reporting.
- Comparing countries only by total emissions. Per-person and historical emissions matter for fairness too.