The remaining global carbon budget leaves little headroom for Europe

As the world fails to reduce emissions fast enough, the remaining carbon budget is shrinking rapidly, as shown by recent studies on carbon budgets for Germany and for Europe.

A recent paper published by AirClim¹ calculates the carbon budget for 42 European countries. Based on the remaining carbon budget to limit temperature rise to 1.5°C with a 66 per cent likelihood, the paper provides an overview of domestic emission reductions needed, and indicates how much funding richer European countries would need to provide to poorer countries within and outside Europe so that they can make similar efforts to stay within the very limited carbon budget that is left.

The results of the AirClim paper largely agree with a similar exercise made by the German Environment Advisory Council (SRU)². The SRU concludes that the remaining carbon budget for Germany is around 2 GtCO₂ for the period starting from 2022. With emissions in Germany in 2020 and 2021 around 0.7 Gt/year, the SRU foresees the German carbon budget for 2020 to 2050 to be 3.4 Gt, while the AirClim paper foresees a budget of 3.8 Gt.

The AirClim paper further identifies the remaining carbon budget for the EU to be around 20 Gt, with the EU also needing to provide 188 bn euro per year to support climate action in other countries, of which 133 bn should be directed towards developing countries. For Germany, its climate finance contribution should be 50 bn per year, of which 36 bn would be directed towards developing countries.

All the above is based on a robust scientific understanding that global temperature rise is almost linearly proportional to the total amount of CO₂ that the world emits (and removes). This knowledge has led to the development of the global carbon budget concept, which identifies the cumulative amount of CO₂ that can be emitted – between pre-industrial times and the moment net cumulative CO₂ emissionsare achieved – to stay within a certain temperature limit. Deducting the amount of CO₂ already emitted from the total carbon budget provides an estimate of the remaining carbon budget.

The contribution of IPCC Working Group I (WG1) to AR6 from August 2021³ provides an estimate of the remaining carbon budgets to limit temperature rise to 1.5°C, 1.7°C and 2°C, with likelihoods between 17% and 83% (see table SPM.2 below). The lower the temperature target and/or the higher the likelihood, the lower the remaining budget. In the AirClim paper the remaining carbon budget is defined by our objective to limit temperature rise to 1.5°C with a likelihood of 66%. This limits the estimated remaining carbon budget for the period 2020 to 2050 to 400 GtCO₂.

The paper then divides the remaining carbon budget across 42 European countries, taking into account that the carbon budget only relates to CO₂ emissions (and thus not to the other greenhouse gases) and that at a global level recent numbers for CO₂ emissions and removals from land-based activities (agriculture, forestry) are rather shaky. The paper basically used two methodologies for dividing the carbon budget:

  • Per capita: whereby countries are assigned a slice of the remaining budget on the basis of their share of the global population;
  • Equity: whereby countries are assigned a slice of the remaining budget taking into account their historical emissions (and responsibility for the climate crisis).

These methodologies are then used to:

  1. define countries’ domestic carbon budgets by using a per capita division of the remaining global carbon budget; and
  2. define countries’ financial obligations to support emission reductions abroad (both within Europe and outside) by using the Climate Equity Reference Calculator4 to define a country’s responsibility and deduct its domestic effort, as defined under (a), to identify how much support the country should give to other countries (or, for countries with a responsibility below their domestic efforts, how much support they should receive from their European neighbours).

A country’s equitable share of the remaining global carbon budget is thus expressed as a domestic carbon budget plus a climate finance obligation (or need).

To identify the domestic carbon budget for each country, we divide the remaining carbon budget of 400 GtCO₂ on the basis of the average of each country’s total population in 2020 and its estimated population in 2050. This means, for example, that the EU27 has a responsibility to reduce emissions by 111 GtCO₂ as compared to BAU (while the EU would emit only 83 GtCO₂ in the BAU scenario). By limiting its domestic carbon budget to 20 GtCO₂, the EU would make a domestic contribution of 63 GtCO₂ towards reducing emissions. This represents a bit more than half of its responsible share of global emission reductions and needs to be complemented by financial support to emission reduction activities abroad.

It should be clear that to stay within the limit set by the Paris Agreement, substantial and transformative action in all parts of the world will be needed, as the remaining global carbon budget is very small. This challenge can only be met if all countries accept their fair share of responsibility, not only by reducing their own greenhouse gas emissions but also by supporting poorer countries and communities to do the same.

Wendel Trio

1Trio, W (2022) Policy Implications of Europe’s Dwindling Carbon Budget. AirClim.
2SRU (2022) Wie viel CO₂ darf Deutschland maximal noch ausstoßen? Fragen und Antworten zum CO₂-Budget.₂_budget.pdf?__blob=publicationFile&v=15
3IPCC WG 1 (2021). Summary for Policymakers. In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group 1 to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change.

 Table SPM.2 | Estimates of historical carbon dioxide (CO2) emissions and remaining carbon budgets. Estimated remaining carbon budgets are calculated from the beginning of 2020 and extend until global net zero CO2 emissions are reached. They refer to CO2 emissions, while accounting for the global warming effect of non-CO2 emissions. Global warming in this table refers to human-induced global surface temperature increase, which excludes the impact of natural variability on global temperatures in individual years.  

Global warming between 1850–1900 and 2010–2019 (°C)   Historical Cumulative CO2 Emissions from 1850 to 2019 (GtCO2)
1.07 (0.8–1.3; likely range) 2390 (± 240; likely range)
Approximate global warming relative to 1850–1900 until temperature limit (°C)a Additional global warming relative to 2010–2019 until temperature limit (°C) Estimated remaining carbon budgets from the beginning of 2020 (GtCO2)
Likelihood of limiting global warming to temperature limitb
Variations in reductions in non-CO2 emissionsc
17% 33% 50% 67% 83%
1.5 0.43 900 650  500 400 300  Higher or lower reductions in accompanying non-CO2 emissions can increase or decrease the values on the left by 220 GtCO2 or more.
1.7 0.63 1450 1050 850 700 550
2.0 0.93 2300 1700 1350 1150 900


In this issue