From carbon accounting to climate accountability: Navigating a multiverse of counterfactual climates

Climate change is characterised by systemic differences between those who drive greenhouse gas emissions and those who experience the greatest impacts. These differences unfold across three interconnected dimensions: the sources of emissions, the unequal distribution of climate hazards, and the discrepancies in vulnerability of specific socioeconomic groups. While attribution science has traditionally linked cumulative anthropogenic emissions to changes in climate hazards, recent advances in source attribution and impact-oriented approaches are now connecting emissions from specific actors to particular hazards and, increasingly, to their associated societal consequences.

Here, we outline how computationally efficient climate modelling tools, such as emulators, expand the scope of source attribution by enabling the exploration of counterfactual climates at scale. This flexibility allows a systematic assessment of how normative assumptions shape attribution outcomes, for example by comparing multiple “emitter lenses” - such as consumption-based versus production-based accounting - each associated with distinct policy instruments and governance contexts.

We illustrate these perspectives using a recent work that attributes present-day extremely hot and dry months to 1990-2020 emissions by income groups, finding that high-income groups disproportionately contributed to the emergence of climate extremes worldwide [1], alongside a complementary study that attributes observed extremes to emissions from fossil fuel and cement producers using event attribution frameworks [2]. Together, these examples highlight how methodological choices and attribution lenses influence quantitative estimates, as well as the challenges associated with moving from carbon accounting to climate accountability.

Exploring the “multiverse” of counterfactual climates can enhance transparency in climate justice debates and support the integration of diverse socioeconomic perspectives into decision-making and legal processes.

 

 

[1] Schöngart, S., Nicholls, Z., Hoffmann, R., Pelz, S., & Schleussner, C. F. (2025). High-income groups disproportionately contribute to climate extremes worldwide. Nature Climate Change, 1-7.

[2] Quilcaille, Y., Gudmundsson, L., Schumacher, D. L., Gasser, T., Heede, R., Heri, C., ... & Seneviratne, S. I. (2025). Systematic attribution of heatwaves to the emissions of carbon majors. Nature, 645(8080), 392-398.