Establishing climate accountability through attribution of climate impacts to GHG emissions within territorial jurisdictions

Typically, responsibility for impacts from aggregate global GHG emissions is attributed proportional to an actor's share of emissions. This way, individual actors are only attributed comparatively small shares of any caused harm and can point to the aggregated responsibility of others far exceeding their own when pressed to take action. This fragmentation of responsibility leads to profound challenges in establishing climate accountability based on principles of international environmental law.

The EUCHR ruling in the Verein KlimaSeniorinnen Schweiz v. Switzerland case states that "each State has its own responsibilities within its own territorial jurisdiction in respect of climate change." Following this argument, we propose an analysis framework to take states' heightened mandate of care towards their own citizens and territories into account, introducing an alternative line of differentiation by experienced impacts.

Using the fast climate impact emulator RIME-X for impact attribution, we quantify national shares of global climate impacts exploring different impact allocation regimes (e.g. area, population, or GDP). We introduce the responsibility-to-harm ratio as the ratio of the share in historic emissions vs. the share in experienced impacts on a national basis. This identifies the percentage of self-inflicted harm vs. harm caused by the conduct of others.

This weighting of national emissions by impacts enables a prioritisation of a state's accountability for domestic impacts. It, thus, partially counteracts the fragmentation of responsibility, making principles of international environmental law more easily actionable. It also provides a simple metric for the inequitable distribution between responsibility for climate change and the impacts it causes, contributing to the quantification of international climate injustice.