How to resuscitate 1.5°C by identifying accountable countries 

Thomas Hahn is associate professor at the Stockholm Resilience Centre and Stockholm University research leader for FAIRTRANS. Robert Höglund is a carbon removal advisor with Marginal Carbon. Mikael Karlsson is associate professor at Uppsala University and research leader for FAIRTRANS. Recent news articles, in the Guardian and from Bloomberg among others, have proclaimed the death of the 1.5°C target given how emissions and lack of sharper commitments are developing. In a new study, in Nature Communications we examine how the responsibility to limit long-term warming to 1.5°C could be allocated after a temporary overshoot, if countries are held accountable in line with the principle of Common But Differentiated Responsibility and Respective Capabilities (CBDR-RC) as established under the UNFCCC.This principle, a cornerstone of climate diplomacy, recognizes that while all countries share responsibility for addressing climate change, their obligations differ based on historical emissions and capacity to act. By comparing countries’ past emissions and future emission claims with their equal cumulative per capita emissions, we establish a new indicator – “additional carbon accountability” – showing countries’ responsibilities beyond current climate targets.If existing national climate targets are met, the 1.5°C fossil carbon budget (for a 50% probability of meeting that goal) will be exceeded with 576 billion tonnes of carbon dioxide (GtCO₂). To meet the 1.5°C target, our indicator shows that the EU, China, the US, and 15 other countries must sharpen their own current targets with faster mitigation and more carbon dioxide removal (CDR), such as afforestation and technical solutions like direct air capture and biochar. All other countries must stick to their national climate plans (nationally determined contributions – NDCs) and net-zero targets.As an example, the EU would need to mitigate or remove an additional 48 GtCO₂ or finance additional reductions beyond current targets in other countries, on top of reaching its own targets in terms of the NDC for 2030 and net zero emissions by 2050. For China, the additional carbon accountability is 150 GtCO₂ and for the USA 167 GtCO₂.Figure 2 from our article Estimating countries’ additional carbon accountability for closing the mitigation gap based on past and future emissions. The figure shows the excessive carbon claims per capita (compared to equal shares) for a 1.5°C budget during 2023–2070 (y-axis) and carbon debt per capita during 1990–2022 (x-axis) for countries of different income levels (colour), based on average populations during the analysed periods.While there is no international agreement on how to operationalize the fairness principles of the Paris Agreement, the new indicator – based on the CBDR-RC – provides an important tool to clarify what different countries are accountable for in relation to the mitigation (emissions) gap. This information feeds d