NEW PAPER: Only 18 countries need to exceed their climate targets to meet 1.5°C

Hot off the press! I am a co-author of a new study in Nature Communications estimating countries' “additional carbon accountability" beyond their current targets.

Who should do what to bring us (back) to 1.5C? It is a normative question, but most would agree that those who have emitted the most should carry the largest responsibility. In the new paper, we introduce a novel indicator to estimate countries' responsibility beyond their climate targets.

We quantified each country’s equal share of the remaining 1.5C carbon budget based on historic carbon debt since 1990 and a per capita share of the remaining carbon budget. This is then compared to countries' future emissions targets, taking into account that some countries will not use their equal budget space, creating the “additional carbon accountability” indicator. 

A striking finding is that using this method, only 18 countries (incl the EU) need to go beyond their current climate targets to meet the 1.5C target. Historic emitters like the EU and the US mainly need to pay off their historic carbon debts, and countries with plans for future large emissions, like China and Iran, set stricter reduction targets. The vast majority of the world's countries have no additional accountability, and “only” needs to meet their stated targets.

However, that makes 1.5C dependent on those with accountability to take it which right now seems unlikely. If countries meet their current pledges, we'll emit 801 Gt of CO₂ through 2070. This is nearly compatible with a 2.0°C target but overshoots the 1.5°C target by 576 Gt CO₂.

Carbon removal is of course the key ingredient in carbon debt repayment. Even if all countries in our dataset with additional carbon accountability would reduce their emissions to zero today, the global carbon budget for 1.5 °C would still be exceeded due to emissions from countries without any additional accountability. For countries to meet their additional accountability net negative emissions is a must as most of them already exceeded their budgets. Only CDR can make them meet their full accountability.

The paper I wrote with Carbon Gap last month All excess emissions must be removed is of course strongly connected to this, and I quoted our pre-print of this new study. The biggest questions is of course how to get countries to take this responsibility.

🌍 Examples of countries' additional accountability beyond reaching their stated 2030 reduction targets and net zero targets: 

European Union: 47 Gt CO₂ (115 tonnes per person)
Iran: 28 Gt (294t per person)
China: 150 Gt (115t per person)
USA: 167 Gt (453t per person)

Full paper and dataset is available for open access at Nature Communications https://www.nature.com/articles/s41467-024-54039-x  

Hahn, T., Morfeldt, J., Höglund, R., Karlsson, M., & Fetzer, I. (2024). Estimating countries' additional carbon accountability for closing the mitigation gap based on past and future emissions. Nature Communications 15, 9707.