What If Country Commitments for CO 2 Removal Were Based on Responsibility for Historical Emissions?

This study explored the consequences of allocating commitments to remove CO 2 to countries according to their responsibility for human-made climate change based on historical (cumulative) CO 2 emissions from fossil fuel use and industry. The ‘carbon debt’ to be restored through CO 2 removal was calculated as the remaining carbon budget for warming by 2 °C minus emissions until 2100. The study included the remaining carbon budget from the recent literature and scenarios for greenhouse gas emissions. This experiment showed that industrialized countries would need to take on the biggest share of CO 2 removal if the calculation of historical emissions starts with the industrial era. If accounting instead starts with the global negotiations on climate policy in 1990, however, developing countries would have to take on the largest commitment for CO 2 removal. Given this scheme and with the aim of settling the carbon debt over two decades with equal annual efforts, the eight countries with the largest shares of historical emissions would have to take on annual CO 2 removal efforts from 1 to 12 Gt CO 2 . These CO 2 removal commitments would imply substantial efforts for many countries but nevertheless depend on the choice of a fairness principle and calculation method to render this operational.