The October 2018 IPCC Special Report (SR15) increased the Global Carbon Budget for a 66% of keeping global temperature increases below the dangerous 1.5 degrees. As a result, we have modified and simplified our charts. The revised carbon budget is 420,000 Mt CO2. Many calculations and charts are still based on the 2014 IPCC report and are biased towards per-capita sharing. (We are working on updating this.)
Civil Society Review Sharing
Playing Nice: how to fairly divide the amount of climate action needed to avoid disaster
IPCC author and senior scientist with Stockholm Environment Institute, Sivan Kartha on how to calculate "fair-shares" of a carbon budget, and why fairness matters in tackling the climate crisis.
This sharing framework was proposed by Civil Society Review in the leadup to the Paris COP in 2015. It is based upon equity and fairness and requires significantly scaled up cooperation between developed and developing countries.
According to their report, FAIR SHARES: A CIVIL SOCIETY EQUITY REVIEW OF INDCS (pdf):
All countries must accept responsibility for meeting at least their fair share of the global effort to tackle climate change. Some countries have much higher capacity to act than others, due to their higher income and wealth, level of development and access to technologies. Some countries have already emitted a great deal for a long time, and thrive from the infrastructure and institutions they have been able to set up because of this. The operationalisation of equity and fair shares must focus on historical responsibility and capacity, which directly correspond with the core principles in the UN climate convention of ‘common but differentiated responsibility—with respective capabilities’ and the ‘right to sustainable development’.
Their assessment of fair shares uses an "‘equity range’, which takes into account:
Historical responsibility, i.e. contribution to climate change in terms of cumulative emissions since an agreed date; and
Capacity to take climate action, using national income over what is needed to provide basic living standards as the principal indicator.