Document MESSAGEix workflows for paper "CoC"

[yiyi1991]

This page consolidates a brief documentation of how the MESSAGE modeling work is applied in the upcoming stand-alone paper led by 2025 YSSP Shuting Fan.

• One-sentence introduction:
  We enhanced the representation of the cost of capital (CoC) in Integrated Assessment Models. We examine how the weighted average cost of capital (WACC) of power generation technologies dynamically reacts to the (cumulative) international climate finance (ICF), and how they shape the decarbonization pathways under different SSPs.

• Rolling title:
  CoC

• Who is involved:
  Authors: Shuting (@shutingfan), Yiyi, Adriano (@adrivinca), Bas (@vruijven), open but with specific interests, see potential next steps

• Branch:
  message-ix-models: https://github.com/iiasa/message-ix-models/tree/coc
  message_data: https://github.com/iiasa/message_data/tree/coc

• Details of the model application:

  • workflow: run by steps, example cli command
    mix-models coc run --from="base" "coc reported" --dry-run
  • key steps:
    • examining how historical international climate financing affects weighted average cost (fe_regression),
    • building assumptions on how future climate financing levels can be and where they flow to (generate_cf),
    • generating wacc and inv_cost,
    • implementing these in MESSAGE (build_coc)
  • input files: in message_data branch
    • the historical climate financing data comes from Shuting's database, International Multilateral Public Climate Finance Dataset from 2000 to 2023. Sci Data 12, 952 (2025). https://doi.org/10.1038/s41597-025-05308-x

• Scenario identifier:
  model name: MESSAGEix-GLOBIOM 2.0-M-R12 Investment

• Starting scenario:
  currently from SSP v5.3, later updated to the 6 finalized SSP 1000f

• Timeline:
  paper submission in 2025 winter or 2026 spring (after SSP scenarios are finalized and released)

• Contact:
  using input data in the private branch for any purpose -> Shuting,
  model application related -> Yiyi,
  effort sharing principles -> Adriano

• SharePoint folder:
  YJ's OneDrive with confirmed co-authors

• Potential next steps:
  The direct constraint on the total available international climate finance (not in a way that they are "translated" into WACC) is not yet there (maybe tied to the share of I in MACRO or to the share of GDP directly?). Contact Yiyi if anyone is interested in a follow-up paper.

This issue will be closed once this paper is released.

Edited Sep 23, 2025.