Allocation Methods: Sufficientarianism and CBDR-RC Principles
1. The Responsibility Approach: Grounding Climate Action in Historical Accountability
The Responsibility Approach allocates the remaining global carbon budget by considering each country’s cumulative emissions and its share of the global population between 1970 and 2050. This timeframe captures both historical responsibility and projected demographic trends, offering a fair and intergenerational lens for climate accountability.
This method aligns with the International Court of Justice’s (ICJ) July 2025 Advisory Opinion, which references key human rights instruments, including the International Covenant on Economic, Social and Cultural Rights (ICESCR), the International Covenant on Civil and Political Rights (ICCPR), and the Vienna Convention, to clarify the legal obligations of states in addressing climate change.
By integrating historical emissions, the Responsibility Approach reflects the ethical imperative that those who have contributed most to the climate crisis must take proportionally greater action to mitigate it. Consistent with the principle of Common but Differentiated Responsibilities and Respective Capabilities (CBDR-RC), this approach places more stringent carbon reduction obligations on high-emitting, industrialized nations, while allowing lower-emitting countries in the Global South greater flexibility to pursue development within ecological limits.
The Responsibility Approach is central to sufficiency-based frameworks like Zero Carbon for All, which translate climate justice into actionable national trajectories and support ethical pathways to the 1.5°C target.
2. The Capability-Driven Allocation: Linking Economic Capacity to Climate Responsibility
The capability-driven allocation method distributes the remaining global carbon budget based on each country’s capacity to act, rather than solely its historical emissions. This approach combines two key indicators: a country’s cumulative population from 1970 to the most recent year available, and its latest GDP per capita (PPP-adjusted). Together, these metrics reflect both demographic weight and economic strength.
Using the same calculation framework as the Responsibility scenario, this method replaces cumulative emissions with a composite capacity share, defined as:
Country Capacity Share = (Cumulative Population × GDP PPP per capita) / Global Total
This approach reflects the principle of Common but Differentiated Responsibilities and Respective Capabilities (CBDR-RC), recognizing that countries with greater financial and technological capacity must shoulder a larger share of global mitigation efforts. It offers a forward-looking framework for estimating the level of compensation owed by overshooting countries to those that remain within their fair carbon share. Thus, addressing both atmospheric appropriation and climate-related damages, and providing a foundation for equitable climate negotiations.
Within sufficiency-based frameworks like Zero Carbon for All, capability-driven allocation ensures that climate targets are not only fair, but also feasible. Thus, anchoring ambition in both justice and practicality.
