The UK's share of the global CO2 budget runs out in 2 years
The UK's per capita share of the global CO2 budget will run out in 2 years (at the end of 2024).
This timescale is very far from what UK citizens have been led to believe, so the calculations are set out here in detail so that readers can decide for themselves.
To stay within 1.5°C of global warming, immediate radical action is needed to phase out the burning of fossil fuels.
What is the CO2 budget?The CO2 released from burning fossil fuels persists in the atmosphere for thousands of years, and so the concentration of CO2 in the atmosphere has been steadily rising for the last 150 years (since large scale burning of fossil fuels commenced).
As the concentration of CO2 in the atmosphere increases, so does the average global temperature. There is a scientific consensus that we must make great efforts to limit global warming to 1.5°C - see document 54.
From the total amount of CO2 emitted by mankind in the past, and the effect it has had, we can estimate the limit to further emissions of CO2 if we are to keep global warming within a particular limit e.g. 1.5°C.
This is known as the CO2 budget (or carbon budget).
By comparing the CO2 budget with current annual CO2 emissions, we can calculate how long the budget will last if no changes are made, which indicates the degree of urgency of action.
The UK's CO2 budgetThe AR6 WG1 report  was published by the Intergovernmental Panel on Climate Change (IPCC) in August 2021. (The IPCC is the United Nations body for assessing the science relating to climate change.)
The report includes figures for the CO2 budget for 1.5°C. The budget calculations had been adjusted slightly since the previous IPCC report of 2018, according to the further information available.
The calculationsThe mathematics are simple, but the conclusion of a timescale of 2 years is so far from what is being discussed that the calculations are set out here in detail, so that readers can decide for themselves.
1. The global CO2 budget to remain within 1.5°C of global warming with 67% confidence is given as 400 billion tonnes CO2 from the start of 2020. This is given on page 38 of the report.
2. Dividing the 400 billion tonnes CO2 between the 8 billion world population gives 50 tonnes CO2 per person as a personal lifetime CO2 budget.
3. Since the UK's emissions are around 10 tonnes CO2 per person per year (document 23), the UK's fair share will last 5 years from January 2020, that is until December 2024 - just 2 years away.
Most people are either unaware or in denial about the severity and urgency of the climate emergency.
Why the 2-year timescale should be common knowledge
- It is what the science says. There is much misinformation about climate change, but the mathematics of this calculation are simple and can be easily checked.
- Other published CO2 budget calculations give similar conclusions (see below).
- The IPCC report of 2018  explained that "rapid and far-reaching transitions", taking just a few years would be needed.
Other sources on CO2 budgets1. Zero carbon sooner: a working paper by the Centre for the Understanding of Sustainable Prosperity at Surrey University (updated 2021)  .
This also concludes (in its preferred analysis - see chart) that the UK's fair share of the remaining global CO2 budget will run out in 2 years - see document 128
2. The Tyndall Centre reports: The Tyndall Centre for Climate Change Research at the University of Manchester has published similar calculations in reports for each UK local authority .
3. Carbon budget calculator https://carbonbudgetcalculator.com/
Why the 2-year timescale is not common knowledge
- UK Government fallacies (see document 106), including
- ignoring emissions from imports in its emissions statistics - see document 111
- ignoring the commitment to global equity enshrined in the Paris Agreement - see document 122
- UK Government deliberate inaction and wrong actions giving a misleading impression
- building of new roads
- expansion of airports
- failure to start of programme of insulation
- self-censoring by climate scientists and NGOs 
- media failings
- lack of scrutiny of Government decisions
- failure to report poor Government decision making
Action neededTo stay within this budget of 50 tonnes CO2 per person, UK citizens need to make radical reductions in emissions (as explained by the IPCC). Some simple maths tells us that reducing the UK average by 20% per year as an exponential decline will achieve this - see chart. A reduction of 20% year-on-year is about the same as halving every 3 years.
In 2022, United Nations Secretary-General Antonio Guterres took the extraordinary step of accusing governments of lying about climate action, saying "Some government and business leaders are saying one thing - but doing another. Simply put, they are lying". He called for the creation of "a grassroots movement that cannot be ignored". Read more at document 136.
Related documentsThe main points on this page have also been published:
- in the British Medical Journal (Sep 2021) UK's share of the global carbon budget will be used up in 3.3 years (letter) BMJ 2021;374:n2391 https://doi.org/10.1136/bmj.n2391 or at https://iancampbell.co.uk/files/bmj.n2391.full.pdf
- as a longer rapid response posted on the British Medical Journal website (Sep 2021) at https://www.bmj.com/content/374/bmj.n1734/rr-7
- as a blog on the website of Scientists for Global Responsibility (Sep 2021) at https://www.sgr.org.uk/resources/uk-s-share-global-carbon-budget-will-be-used-just-over-3-years
|||IPCC (Aug 2021) AR6 Climate Change 2021: The Physical Science Basis https://carbonindependent.org/files/IPCC_AR6_WGI_SPM.pdf (downloaded 21 Aug 2021) or https://www.ipcc.ch/report/ar6/wg1/ https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM.pdf|
|||IPCC (Oct 2018) SR15 Summary for policymakers https://www.ipcc.ch/site/assets/uploads/sites/2/2018/07/SR15_SPM_version_stand_alone_LR.pdf|
|||Turning delusion into climate action - Prof Kevin Anderson, an interview (2020) Responsible Science https://www.sgr.org.uk/resources/turning-delusion-climate-action-prof-kevin-anderson-interview|
|||Jackson T (2021) Zero Carbon Sooner: Revised case for an early zero carbon target for the UK. CUSP Working Paper No 29. Guildford: University of Surrey. https://cusp.ac.uk/wp-content/uploads/WP-29-Zero-Carbon-Sooner-update.pdf|
|||Tyndall Centre The Tyndall carbon budget tool (2019) https://carbonbudget.manchester.ac.uk/reports/|
First published: 28 Sep 2021
Last updated: 14 Sep 2022