A Capping Scheme
The Princeton proposal establishes a uniform "cap" on emissions that individuals should not exceed (represented by the green line). If, for example, an international treaty caps global emissions at a certain level, the necessary reductions in global emissions could be achieved if no individual's emissions could exceed a certain "cap." By counting the excess emissions of all the individuals who are projected to surpass the "cap" (red arrows), the proposal provides emissions reduction targets for each country (blue arrows).

(Image: Courtesy of PNAS)