Equitable cooperation explorer

About the paper

Equitable cooperation deepens the solution space for high ambition pathways (Pelz et al., 2026, Environmental Research Letters) asks what changes when fairness is a design constraint during scenario generation. Starting from a cost-optimal pathway to 2 °C or 1.5 °C, each region must meet a principle-based fair share of the carbon budget and may cooperate with others to do so. Two corners bound the result: with unlimited transfers the physical pathway is unchanged and the fair share is settled by financial transfers; with transfers held to the lowest level the model tolerates, higher-responsibility regions cut faster at home and the global fossil exit accelerates, at a modest and progressive cost. The paper page has the question, the approach and the findings in full.

The paper's main figures, redrawn from the same scenario data with the same aggregation as the paper's figure code. The Explorer tab draws the indicators of climate action for every pathway, by region and by budget. Every mark carries a value: hover for it. Hover a legend chip, a line, a bar or a label to follow one approach, one cooperation scope, one budget or one region across the panels of a figure. Click to keep it; further clicks add others, and a click on a kept item or on show all releases it. Each figure's data can be downloaded as a table.

How to read these figures
Fair shares and carbon debt. Each region receives a share of the carbon budget under a fairness principle. A region that has already used more than its share carries a debt. It can pay the debt down by cutting emissions faster at home, by removing emissions at home, or by financing action in other regions.
The two corners. Under unlimited transfers (U, up-pointing triangle in the paper figures) finance between regions is unlimited, the physical transition matches the cost-optimal source pathway, and the fair share is settled by financial transfers. Under lowest transfers (L, down-pointing triangle) finance is held to the lowest level the model tolerates, the higher-responsibility regions cut fossil fuels faster at home, and the regions with less historical responsibility gain room relative to the source pathway. A cross marks the source pathway.
The fair-share variants. ECPC shares the budget by equal cumulative emissions per person, CAPC adjusts that share for capability, and the year is when responsibility starts to count (1990, 2015 or 2025). The default pair is ECPC 2015 on the SSP2 narrative. ECPC 2015* is ECPC 2015 with a ten-year delay before transfers begin. Further pairs change the narrative (SSP1), the cooperation channel (novel carbon removal only) or the discount rate (1%). Each pair has both corners.
The carbon budgets. Two budgets, both counted from 2020 and both allowing overshoot: one consistent with about 2 °C at a two-in-three chance and one with 1.5 °C at an even chance. The budget binds the emissions the fair-share rules cover. Land use, international shipping and aviation sit outside it, so total CO₂ over 2020 to 2100 lands within a few percent of the budget for every line.
Transfers, investment and consumption. Transfers and investment are present values at 2025 of flows from 2026, in market exchange rate dollars. Consumption changes are the same present value against the no-new-policy baseline or against the source pathway.