Methodological aspects of the tolerable windows approach

The tolerable windows approach (TWA) allows the climate policy formulation process to be safeguarded in the following way. First, guardrails are defined in order to exclude intolerable climate change impacts, on the one hand, and unacceptable socioeconomic consequences of climate change mitigation measures, on the other. Second, a scientific analysis is conducted to investigate the features of those emission paths that are compatible with the guardrail constraints. The fundamental methodology of the TWA is best described in terms of the theory of differential inclusions. This emerging mathematical theory already provides numerical methods applicable as long as the underlying integrated assessment models are of limited complexity. In order to identify emissions corridors, we propose a novel calculation scheme applicable also for large-scale integrated assessment models.