Reference values to the NDCs resp. NDCs calculators:
Regensburg Model and Extended Smooth Pathway Model

Short introduction

Distribution of a global CO2 budget

CO2 affect the climate for a long time. Therefore, remaining global CO2 budgets correspond to certain limits of global warming (more information here).

Which concrete global budget we want to orientate by 2100, however, must ultimately be decided politically on the basis of the current state of scientific knowledge.

Such a global budget raises the question of how it can be distributed amongst the countries in a fair and economically reasonable way. Such a distribution should be an important guidance of the ratchet up mechanism (ambition mechanism) of the Paris Agreement with Nationally Determined Contributions (NDCs).

Here two models are presented to calculate national paths and budgets that are compatible with a given global budget 2018 - 2100:

In addition, resource sharing models are compared and a tool for determining global paths is offered.

Basic idea behind the Regensburg Model (RM)

  1. Global paths: Global emission paths are determined that are compatible with a global CO2 budget to be specified. For this purpose, the 'Tool_RM' provides six scenario types (RM 1 - 6), which differ in their assumptions about the course of the annual reductions.
  2. National paths: National emission paths are derived from this global paths in the convergence period with the Regensburg Formula, which leads to the convergence of per capita emissions.
Latest publication on the Regensburg Model (further publications here):
Journal "Climate Policy" published online on 14 June 2016:
The Regensburg Model: reference values for the (I)NDCs based on converging per capita emissions

Basic idea behind the Extended Smooth Pathway Model (ESPM; inspired by Raupach et al.)

  1. National budgets: A predefined global CO2 budget is distributed to countries. The 'Tool_ESPM' offers the use of a weighted distribution key that includes the 'population' and the 'emissions' in a base year (here: 2019).
  2. National paths: The 'Tool_ESPM' offers the Regensburg Model scenario types RM 1 - 6 to derive plausible national paths from a national budget.
Notes on the relationship between ESPM and RM:
Depending on the chosen global path and the chosen convergence level, there is an implicit weighting of the population in the resulting national budgets in the RM. The use of this implicit weighting as an explicit weighting in the ESPM leads to very similar results as in the RM, as this overview of the results according to ESPM and RM shows for the largest emitters.

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