DOI: 10.5281/zenodo.14356271
title: Fair emissions allocations under various global conditions

description: Introduction

This dataset contains information on how to fairly distribute the mitigation efforts that countries need to undertake to together achieve certain climate goals. There is no single answer to this question, but we explore this topic by looking at various global emissions pathways, and subsequently allocate these emissions to countries using different effort-sharing rules. This data is applied in a preprint of a scientific article where we explore implications of justice on NDCs and international mitigation finance.

The research behind this dataset is still under development and therefore this dataset is not final. Our scientific work is still under revision so the data is subject to potential changes upon peer review of this publication. Nevertheless, because (a version of) this data is already used in the Carbon Budget Explorer and in scientific projects, we feel it should be available and versioned. Hence these releases of a preliminary version.

Carbon Budget Explorer

We also published this work on a website called the Carbon Budget Explorer: an online interactive tool that allows users to navigate through these results, without having to download and plot the data themselves. It is free and publicly available at www.carbonbudgetexplorer.eu. Currently, the Carbon Budget Explorer relies on a previous version of this dataset (version 0.1, unpublished, but available upon request). The Explorer will be updated with new data early 2025 (i.e., with the version presented in this data repository).

Data description

Default (DefaultAllocations.zip and DefaultReductions.zip)

For many users, these are the main datafiles. Per country and region, allocations and reduction targets are shown for two trajectories, which are associated with 1.5 (with slight overshoot: peak temperature 1.6) and 2.0 degree pathways, and default settings across all other dimensions. The exact parameters used in these precooked pathways are shown in Table 1 (see "Dimensions"). The reductions_default_*.csv files show data along the same structure, also using the default pathways, but contain the emission reductions with respect to 2015 rather than absolute allocations.

Global pathways (GlobalPathways.zip)

Allocating emissions to countries starts with determining global emissions pathways. The files in GlobalPathways.zip contain projected global emissions on GHG, CO2 and non-CO2 levels, constrained by various global settings (see below) such as temperature targets and derived CO2 budgets. The pathway shapes are informed by mitigation scenarios from the IPCC AR6 database. The starting values are all harmonized with 2021 historical datapoints. For convenience, the emissionspathways_default.csv datafile provides the pathways with default settings (see Table 1, column 'Default'). The complete dataset can be found in emissionspathways_all.csv.

Emission allocations (Allocations.zip -> allocations_*.nc)

The emissions from the global pathways can be divided among countries according to different allocation rules (see 'Allocation rules' for more information). Files of the format allocations_region.nc indicate allocations according to all allocation rules, parameters and global choices, for a single region. Because of the high number of parameters and dimensions, these files are shared in NetCDF (.nc) format. NetCDF files are commonly used for storing multidimensional scientific data and can be displayed, analyzed and read/written using GIS systems (such as ArcGIS, QGIS), MATLAB funcions (such as nccreate, ncread), R (e.g. using the ncdf4 package) and Python (e.g. using the xarray package).

Input data (Inputdata.zip)

Additional input data coming from third parties, such as population and GDP data, is stored in Inputdata.zip. We prepared these input data sources in the exact same format as the rest for convenience of the user, but we would like to emphasize that the appropriate references should be cited. For further information, please check 'Input data sources'.

CO2 budgets

A file has been added in the version 0.3.1, including cumulative CO2 budgets. How they are calculated, is slightly different for each rule (only PC, AP and ECPC are included here), because of the varying nature of these allocation rules. The PC budget is simply the fraction of the remaining carbon budget determined by a country's 2021 population share. The AP budget is computed by adding all positive CO2 allocations according to the AP rule. The ECPC budget is the full-century budget: that is, historical leftover (or debt) plus a country's fair per capita share between 2021-2100. Note that there is not necessarily a one-to-one relation between these budgets and the CO2 part of the allocation files (Allocations.zip). For example, the PC budget uses 2021 population, while the allocation files use year-to-year population numbers (also if they change in the future). We have the ambition to, in next versions, expand this dataset to account for and vary the choices one can make in this regard.

Allocation rules

Below you can find a summarized description of all allocation rules. More detailed information can be found in Van den Berg et al. (2020), as well as in a scientific paper (preprint) expected in summer 2024. The rules have a variety of parameters, each included as dimensions in the data. See Table 1, in "Dimensions", for details.



The (immediate) 'Per Capita' method (PC) uses a country's population share in the global population and allocates future emissions accordingly. Naturally, socio-economic conditions affect this method. Therefore, all five SSPs are used in our analysis. 

'Grandfathering' (GF) is a method that preserves current emission fractions. In other words, all countries reduce their emissions proportional to their current share. Note that this rule is controversial and is commonly not regarded as fair (see Rajamani et al. 2021). It is include here for reference only.

The 'Per Capita Convergence' (PCC) method starts as 'Grandfathering', but converges over time to a 'Per Capita' basis. An additional important parameter here is the year at which this convergence completes.

The 'Per Capita via Budget' (PCB_lin) method is a specific implementation of distributing the total CO2 budget on a per capita basis, and then drawing a linear line from current emissions down to net-zero CO2. A median non-CO2 path is added to end up with a total greenhouse gas emissions line. This is similar to, for example, Fekete et al. (2022).

The 'Ability to Pay' (AP) method allocates emissions inversely related to the GDP per capita of countries. Also this method is dependent on the socio-economic scenario.

The 'Equal Cumulative Per Capita' (ECPC) method builds on the per-capita convergence method, also accounts for historical responsibility: throughout the convergence period, countries resolve historical 'debt' or 'leftover' from what countries would have emitted if it had emissions according to a per capita share in the past. Note: this method has been significantly revised in version 0.4. In earlier versions, resolving of historical responsibility was only achieved by 2100, postponing most debt.

The 'Greenhouse Development Rights' (GDR) method is, in the short run, based on a Responsibility-Capability Index, and in the long run based on GDP per capita (similar to 'Ability to Pay').


Dimensions

Table 1 - Data dimensions




Name
Unit
Range
Default
Description


General
 
 
 
 


Time
Year


Past: 1850-2021

Future: 2021-2100 (yearly or 5-year increments)

All
The historic data reported here ends in 2021, and we start our analysis in 2021. Intentionally, to be able to exactly match historic and future data. The year 2021 is chosen because of limited availability of more recent data sources.


Region
ISO3 code


Country-level (ISO3)

Country groups (e.g., G20 and Umbrella)

World ('EARTH')

All
 


Global
 
 
 
 


Temperature
Degrees temperature rise with respect to pre-industrial times


1.5 - 2.0 degrees

1.6 and 2.0
Peak temperature without overshoot


Climate sensitivity ('Risk' in the data)
Risk of exceeding a certain climate target, based on climate sensitivity percentiles.


17%, 33%, 50%, 67%, 83%



50% (for 1.6 degrees) and 33% (for 2.0 degrees)



This governs the uncertainty in climate sensitivity. Because there is still uncertainty about the exact numerical response of temperature to CO2, we have to include this. Low-risk (e.g., 0.17) indicates that we assume a high climate sensitivity: for a given amount of greenhouse gas emissions, temperature rises higher. This means that carbon budgets at a given temperature level have to be lower. Vice-versa for high-risk (e.g., 0.83).



NegEmis
Quantiles of 2100 GHG emissions among AR6 scenarios with a similar temperature target


17%, 33%, 50%, 67%, 83%



50%



Even though negative emissions (predominantly in the second-half of the century) are not very relevant for achieving a certain peak temperature, they do alter the second half of global emissions pathways.



NonCO2red
Quantiles of non-CO2 reductions in 2040 with respect to 2020 among AR6 scenarios with a similar temperature target


17%, 33%, 50%, 67%, 83%

50%
Non-CO2 reduction varies greatly among mitigation scenarios, but at the same time has a large effect on the remaining carbon budget. Hence, we vary this factor.


Timing
-


Immediate or Delayed

Immediate
The timing of mitigation action up to 2030. Either this starts immediately (2020) or only after 2030. This factor distinguishes mitigation scenarios from which the functional form of the global emissions pathways are constructed.


Parameters in allocation rules
 


 

 
 


Scenario
SSP


SSP1-5

SSP2
Shared-Socioeconomic pathway, defining population and GDP data based on a scenario of how to perceive the future world.


Convergence_year
Year


2040, 2050, 2080, 2100

2050
Year of convergence for the per capita convergence and equal-cumulative per capita rules.


Discount_factor
% per year


0%, 1.6%, 2%, 2.8%

0%
Discount factor of historical emissions, counting from the startyear 2021.


Historical_startyear
Year


1850, 1950, 1990

1990
Year from which and on historical emissions are accounted for in the computation of the responsibility of countries.


Capability_threshold
-


No, PrTh, Th

Th
Implicates whether an additional development threshold should be implemented for the computation of the capability of a country to contribute to mitigation. This is used in the calculations of the Greenhouse Development Rights rule. Entries are (1) no development threshold (No), (2) a threshold of \$7500 (Th) or (3) the \$7500 threshold plus additional progressivity factors. For more information, see Holz et al. (2019).


RCI_weight
-


Cap, Half, Resp

Half
Distinguishes how the Responsibility-Capability Index in the Greenhouse Development Rights rule should weight capability (fully = Cap) or responsibility (fully = Resp). 'Half' indicates that both factors should weigh equally.




Input data sources

For most important data sources, aggregated regions (e.g., G20 and the Umbrella group) are not reported in the original data sources below. We did that aggregation ourselves.



Historic population: UN population data

Future population: SSP database

Future GDP: SSP database

Historical emissions: Jones et al. (2023)

Emissions pathways (shapes): Byers, E. et al. AR6 Scenarios Database.  (2022)

NDC data: PBL NDC tool

Carbon budgets: Forster et al. (2023)

Impact of non-CO2 on carbon budgets: Rogelj et al. (2024)


Changelog



Version 0.4:



Equal-cumulative per capita is significantly revised in terms of temporal allocation. This has large consequences for short-term allocations in most countries, depending on the convergence year. See description above under 'Allocation rules'.

Data is now also available for different analysis starting years, gases and including or excluding LULUCF. This is upon request because this would make the repository too large.

In the same spirit, a selection has been made on what to include in these datafiles for completeness and clarity, and what to omit to limit file size and computation problems. If you need any specific parameter combination that you cannot find here, feel free to contact us.

Improved data on historical population data and baseline emissions

Added units in CSV datafiles



Version 0.3.1:



Added CO2 budgets for additional combinations of global targets (no changes in allocation values)



Version 0.3:



Fixed small error in regional aggregation

Cumulative CO2 budgets for PC, AP and ECPC are added in a new file

Updated global baseline emissions, which affects AP and ECPC



Version 0.2:



Significant update on LULUCF emissions data and historical emissions data by changing to a more up-to-date data source

NDC data update (now from the PBL NDC tool)

Added the per-capita via budget rule

All the above affect emissions allocations, which are therefore also updated



Version 0.1:



First version of the data

Published on the Carbon Budget Explorer




Contact

We are very open to suggestions of all kinds. Feel free to contact Mark Dekker at this email address or at the contact form on this website.