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Global carbon budgets · IPCC AR6

CO2 budgets published by the IPCC

From remaining global CO2 budgets to global emission paths and
Paris-compatible national CO2 budgets.

The Paris temperature goal

The overarching objective of the Paris Agreement is to hold “the increase in the global average temperature to well below 2°C above pre-industrial levels” and to pursue efforts “to limit the temperature increase to 1.5°C above pre-industrial levels.”

Remaining global CO2 budgets

Remaining global CO2 budgets from 2020 onward according to the IPCC Sixth Assessment Report, for different global warming levels, with an 83% probability of staying below the respective warming level.

Warming
[°C]		 Estimated remaining carbon budgets
[GtCO2 from 2020 on]
1.5 300
1.6 400
1.7 550
1.8 650

We currently emit around 42 Gt CO2 per year.

Detailed background paper

Temporary carbon-budget overshoot

Since staying directly within these budgets can no longer be considered realistic, a temporary carbon-budget overshoot would have to be offset by net negative CO2 emissions. More information can be found here.

CO2 clock

The PIK's CO2 clock is based on a 67% probability of staying below the respective warming level (1.5°C: 400 Gt; 2°C: 1,150 Gt) and asks how long the global budget would last if global CO2 emissions remained at today's level.

From global budgets to emission paths and national budgets

The following web apps use a predefined global CO2 budget as a starting point for further calculations.

Web apps

Global paths

Two web apps calculate global emission pathways consistent with a predefined CO2 budget:

Linear paths

Calculates linear global emission paths consistent with the specified CO2 budget.

Screenshot of the linear global emission paths web app global-paths.climate-calculator.info
Detailed version – RM Scenario Types

In addition to linear paths, this app provides further pathway types (RM Scenario Types) designed to cover the full spectrum of plausible global emission trajectories. It also allows direct comparisons of emission paths and annual emission change rates.

Comparison of five global RM emission pathways, including annual emission change rates and CO2 budgets paths.climate-calculator.info
Web apps

National CO2 budgets

Web apps for calculating Paris-compatible national CO2 budgets. Two versions are available:

Screenshot of the national CO2 budgets web app
Short version

Compact access to the national budget calculation.

short.national-budgets.climate-calculator.info
Detailed version

Offers additional features, such as a direct comparison with the NDCs of the six largest emitters.

national-budgets.climate-calculator.info

Both web apps take two key criteria into account, with freely adjustable weights:

  1. Share of global CO2 emissions – current reality
  2. Share of global population – climate justice

For the underlying allocation criteria, see the corresponding excursus here.

The national budget web apps presented here use linear emission pathways. For additional pathway options, see our Extended Smooth Pathway Model (ESPM) and the associated RM Scenario Types.

Meeting national CO2 budgets

National CO2 budgets can best be met through hard caps in emissions trading systems. To ensure that the resulting ‘whatever-it-takes CO2 prices’ can be politically enforced and are fair, the entire auction proceeds should be distributed back to citizens as a per capita lump sum (climate dividend).

In parallel, efforts should be made to agree on standards for particularly CO2-intensive processes and activities — such as steel production, cement production, certain basic chemical processes, international aviation and shipping — within a coalition of the willing (climate club).