New research led by the International Institute for Applied Systems Analysis (IIASA) suggests that incorporating principles of fairness into climate models can create more diverse ways to reduce emissions while still meeting global climate goals. Published in Environmental Research Letters, the study shows that when emissions budgets are divided based on fairness—considering factors like historical responsibility and economic strength—different regions can achieve climate targets through a mix of cutting emissions and offering financial support to others. This approach allows for flexibility in how the global effort to reduce emissions is shared. The study used a complex modeling framework called MESSAGEix-GLOBIOM-GAINS to explore scenarios that keep global warming below 2°C with a 67% chance of success. Researchers compared two methods for meeting each region’s fair share of emissions cuts: one where regions could freely transfer money to help each other, and another where such transfers were limited. When financial support was restricted, regions with higher historical emissions cut their own emissions more quickly, leading to a 3% to 21% drop in global fossil fuel use by 2040. However, the overall path toward renewable energy and total emissions by 2100 stayed the same. The economic cost of including fairness in the models was found to be relatively low. In the most efficient pathway, global consumption dropped by about 0.8%, and this increased to a maximum of 1.3% when fair-share principles were applied and transfers were limited. Interestingly, regions with lower historical emissions and economic capacity saw improvements in their consumption levels compared to the cost-effective pathway in all scenarios. The researchers stressed that including fairness in the early stages of creating climate scenarios changes how the transition to a low-carbon world is structured, without affecting the ultimate climate goal. Typically, fairness is considered after identifying the most cost-effective path, but starting with fairness reveals new ways to distribute the effort. This approach highlights that different regions can share the burden of emissions reduction in various ways while still achieving the same global outcome. The study also looked at a scenario aiming to limit warming to 1.5°C by 2100, with temporary exceedance allowed. While multiple pathways were still possible, there was less flexibility in where emissions cuts occur, meaning financial support became even more important. Compared to the 2°C scenario, the amount of financial support needed nearly doubled when transfers were free, and remained close to that level when transfers were limited due to physical constraints on emissions reductions. The researchers emphasized that financial transfers in this context refer to overall flows between regions, not specific market mechanisms. They urged future climate assessments to regularly consider both cost-effective and fair-share pathways, especially as countries prepare their next climate commitments and the upcoming Global Stocktake. An interactive online tool developed by the researchers allows users to explore the study’s findings in more detail.