Effects of emissions allocations and ambition assessments immediately based on equity

Abstract National emissions targets are collectively insufficient to align with the Paris Agreement. The literature quantifying national emissions trajectories based on equity principles will inform the Global Stocktake on the ambition of national 2030 targets. Ambition assessments based on trajectories that start at present-day emissions levels inherently reward past inaction thus far, and increasingly do so into the future. Here we quantify emissions trajectories based on equity principles applied with immediate effect. We find national targets of G7 countries, Russia and China responsible for most of the global ambition gap, while only those of some countries in the Global South align with their 1.5°C allocation. Discontinuous trajectories not starting at current emissions levels imply stronger international support that can mobilize the capital needed to implement the 1.5°C trajectory globally. The difference between allocation with or without discontinuity has remarkable consequences for the relative implied contributions among high-income countries to international support.