Quantifying national responsibilities for climate change impacts

The extent to which damage caused by climate change can be attributed to a particular country or group of countries has become a central debate in climate justice. Thus far, historical emission levels have been used to discern responsibilities for climate change. However, this metric fails to attribute specific climate change damages to the responsible countries, and does not establish a causal link to the scale and distribution of impacts in space and time. To overcome this shortcoming, we quantify the marginal costs each country bears due to the emissions from all other countries. We do so through a country-to-country mapping transparently linking historical emission levels to estimates of costs incurred from climate change impacts, thereby establishing a quantitative basis of direct political relevance. For each country, we derive the net costs as the difference between costs incurred to other countries through its emissions, and those endured as a result of other countries’ emissions. We find that a group of high emitting countries incur net costs to other countries of US$43.7 trillion, increasing by roughly US$500 billion annually. The full implementation of current mitigation pledges would do little to reverse this trend, as costs accumulate over time, long after greenhouse gases are emitted. These findings highlight that the premise behind the current international climate finance framework—which is based on voluntary contributions—is profoundly unjust. We provide quantitative estimates that help underpin a more just framework.