Allocation of the residual global CO2 budget between countries

How should the residual CO2 budget be divided between countries?

In order to be confident of keeping global warming to less than 1.5°C, further global CO2 emissions must be kept below a total of 400 billion tonnes since 2020 - see document 54. This 400 billion tonnes is known as the residual carbon CO2 budget (or carbon budget); it is currently dwindling at a rate of 34 billion tonnes CO2 per year.

A vital question on which there is little discussion is what principle should be used to divide this residual CO2 budget between countries.

Possible ways of dividing the residual CO2 budget

Considerations in dividing the residual CO2 budget


The only justifiable principle for allocation of the residual CO2 budget is that the developed countries take no more than their fair per-capita share.

Who is advocating a fair (per capita) allocation of the residual carbon budget?

Who is advocating that developed countries take more than a per capita allocation of the residual CO2 budget?

Many governments of developed countries are planning to take much more than an equal per-capita share in their climate plans. For example the UK Government in its 368-page Net Zero Strategy of October 2021 [5] shows an emission reduction pathway that is approximately a steady (i.e. linear) decline from its current annual 10 tonnes CO2 per person to zero in 2050 - which is an average of 5 tonnes per person per year for 30 years - which is a total of 150 tonnes CO2 per person. This 150 tonnes is 3 times the global per capita share of 50 tonnes - see document 54. There is no mention of equity between countries in the document - the only mentions of 'equity' are in the form of 'equity investment', 'private equity', 'equity capital' and 'equity shares'. Furthermore, there is a fallacious implication in the Foreward from the Prime Minister that the document represents a satisfactory response to the climate emergency in his claims "We will meet the global climate emergency" and "we set an example to the world".


[1]Rio Declaration on Environment and Development (at the Rio United Nations Conference) (1992)
[2]The Paris Agreement (2015)
[3]"Zero carbon sooner" carbon budget report from CUSP
[4]Tyndall Centre The Tyndall carbon budget tool (2019)
[5]UK Government Net Zero Strategy: Build Back Greener (Oct 2021)

First published: 25 Oct 2021
Last updated: 17 May 2023