The Climate Change Act 2008 is the United Kingdom statute that legally requires the government to cut net greenhouse gas emissions to zero by 2050, measured against 1990 levels. It works through binding five-year carbon budgets, an independent expert committee, mandatory reports to Parliament, and a right of judicial review that has already been used to strike down inadequate government plans. Rather than a political pledge, it creates statutory duties the courts can enforce.
The 2050 Net Zero Duty
Section 1 places a direct legal duty on the Secretary of State to ensure the UK’s net carbon account for 2050 falls below the 1990 baseline.1Legislation.gov.uk. Climate Change Act 2008 When the Act first passed, the target was an 80 percent reduction. In 2019, the Climate Change Act 2008 (2050 Target Amendment) Order raised it to 100 percent, committing the UK to net zero.2House of Lords Library. Climate Change Targets: The Road to Net Zero
Net zero does not mean no emissions. It means total greenhouse gases emitted must be balanced by removals from the atmosphere, so some emissions can continue provided an equivalent amount is captured or offset. Because this sits in statute rather than in policy, missing the target exposes the government to legal challenge.
How Carbon Budgets Work
A single 2050 deadline would let any government defer action. Section 4 closes that loophole by requiring the Secretary of State to set a carbon budget for every five-year period from 2008 onward, and to keep actual UK emissions inside that cap.3Legislation.gov.uk. Climate Change Act 2008 – Section 4
Budgets have to be set far in advance. After the first three (covering 2008–2022), each budget must be in law no later than 30 June of the twelfth year before the period it covers.3Legislation.gov.uk. Climate Change Act 2008 – Section 4 The sixth budget, covering 2033–2037, had to be in place by 30 June 2021. The practical effect: an incoming government inherits legally binding emissions caps set by its predecessors and cannot walk away from them without amending the law.
Six budgets have been set, each tighter than the last:4GOV.UK. Carbon Budgets
- First budget (2008–2012): 3,018 MtCO2e
- Second budget (2013–2017): 2,782 MtCO2e
- Third budget (2018–2022): 2,544 MtCO2e
- Fourth budget (2023–2027): 1,950 MtCO2e
- Fifth budget (2028–2032): 1,725 MtCO2e
- Sixth budget (2033–2037): 965 MtCO2e
The sixth budget represents a cut of nearly 45 percent on the fifth. It was set at 965 MtCO2e on the Climate Change Committee’s recommendation and is the steepest reduction the UK has yet committed to in law.4GOV.UK. Carbon Budgets
The Climate Change Committee
Part 2 of the Act creates the Committee on Climate Change (CCC) as an independent expert body. Under Schedule 1, it has a chair and between five and eight further members appointed by the national authorities, chosen for scientific and economic expertise.5Legislation.gov.uk. Climate Change Act 2008 – Schedule 1
Its central job is advising the Secretary of State on the level of each carbon budget. Before setting a budget, the Secretary of State must formally request and consider the CCC’s recommendation. The committee also produces annual progress reports to Parliament assessing whether the government is on track. Those reports are statutory, not discretionary, which forces public scrutiny into the timetable.
A separate Adaptation Sub-Committee (now the Adaptation Committee) sits within the CCC, with a chair and at least five members, focused on the physical impacts of climate change on the UK.5Legislation.gov.uk. Climate Change Act 2008 – Schedule 1
What the Government Must Publish
Setting a cap achieves nothing without a plan for staying under it. Section 13 requires the Secretary of State to prepare proposals and policies capable of meeting each carbon budget and the 2050 target, and those plans must also contribute to sustainable development.6Legislation.gov.uk. Climate Change Act 2008 – Section 13 Section 14 requires those proposals to be laid before Parliament as soon as reasonably practicable after a budget is set. That sustainable development wording has since become the pivot of real litigation.
Section 16 requires an annual emissions statement to Parliament covering total UK greenhouse gases and the net carbon account for the year.7Legislation.gov.uk. Climate Change Act 2008 – Section 16 At the end of each five-year budgetary period, a final statement confirms whether emissions stayed within the cap. If the budget is exceeded, the Secretary of State must explain the failure to Parliament and set out proposals for compensating in later periods.8Legislation.gov.uk. Climate Change Act 2008 – Section 19
Trading Schemes
Part 3 gives the government power to create trading schemes to limit greenhouse gases. Section 44 allows a national authority to establish schemes that either cap emissions-producing activities or reward activities that reduce or remove greenhouse gases, covering both direct emitters and indirect contributors such as energy use.9Legislation.gov.uk. Climate Change Act 2008 – Part 3: Trading Schemes
After the UK left the EU Emissions Trading System on 1 January 2021, the UK Emissions Trading Scheme was launched as a standalone cap-and-trade replacement covering aviation, power generation, and heavy industry. Each allowance represents one tonne of CO2 equivalent, and covered businesses must surrender enough allowances every year to match their actual emissions.10GOV.UK. UK Emissions Trading Scheme (UK ETS): A Policy Overview
International Aviation and Shipping
Emissions from international flights and shipping sat outside the carbon budgets for years. Section 30 lets the Secretary of State bring them in by regulation, and that power has now been used. The Climate Change Act 2008 (International Aviation and International Shipping) Regulations 2026 require the UK’s share of those emissions to count toward the carbon budget from the sixth budgetary period (2033–2037) onward.11Legislation.gov.uk. The Climate Change Act 2008 (International Aviation and International Shipping) Regulations 2026 The 965 MtCO2e cap now has to accommodate emissions that were previously off the books.
Adaptation Planning
Cutting emissions is only half the Act. Part 4 addresses the impacts already locked in. Section 56 requires the Secretary of State to lay before Parliament a report assessing the risks climate change poses to the UK, with the first report due within three years of the section coming into force and further reports every five years.12Legislation.gov.uk. Climate Change Act 2008 – Section 56 Each risk assessment must take account of CCC advice, and each is followed by a National Adaptation Programme setting out the government’s response.
The Act also carries an Adaptation Reporting Power, letting the Secretary of State direct organisations with public functions to report on how they are preparing for climate impacts, including current and predicted effects and their plans for adapting.13GOV.UK. Adaptation Reporting Power – FAQs
How the Act Is Enforced
The Act sets no fine for missing a carbon budget. Enforcement runs through judicial review, and it has worked in practice.
In 2022, the High Court ruled in R (Friends of the Earth) v Secretary of State for Business, Energy and Industrial Strategy that the government had breached Sections 13 and 14. The court found that the Net Zero Strategy laid before Parliament failed to include adequate information on how individual policies would contribute to meeting carbon budgets, and that the Secretary of State had approved it without being properly briefed on critical gaps in the quantitative analysis.14Judiciary.uk. Friends of the Earth v BEIS Judgment A compliant report was ordered by 31 March 2023.
The government’s replacement Carbon Budget Delivery Plan was laid on that deadline. Friends of the Earth, ClientEarth, and Good Law Project challenged it again. In May 2024, the High Court ruled against the government on four of five grounds, finding that the Secretary of State had failed to account for delivery risks, had proceeded on the irrational assumption that every policy would be implemented in full, and had applied the wrong legal test to the sustainable development requirement in Section 13.15Judiciary.uk. Friends of the Earth and Ors v SSDESNZ
The practical lesson from both rulings is that an optimistic plan is not enough. Proposals under the Act have to be credibly quantified and grounded in realistic delivery assumptions, and where they are not, the courts will intervene.