Shared Policy Assumptions (SPAs) ¶

The Shared Policy Assumptions (SPA) are four packages of climate policy instruments (SPA1 to SPA4) with different levels of ambition and intervention. There is also an SPA0, which describes the status quo of existing climate policy instruments in 2024. Based on political science literature, the SPAs were developed along two central dimensions - the level of ambition of climate policy and the depth of intervention of the policy instruments. The SPAs thus cover a broad spectrum of possible climate policies:

• SPA0 - Status Quo
• SPA1 - Green State: Ambitious targets, strong state intervention.
• SPA2 - Ecological Republic: Ambitious targets, rather low state intervention (e.g. voluntary measures by civil society and business)
• SPA3 - Market-Liberal State (also: Ordoliberal State): Low level of ambition, minimal state intervention
• SPA4 - Conserving State (also: Compensating State): Strong state intervention, which does not serve climate goals but other policy goals (e.g. curbing energy costs)

A total of 7 combinations were modeled: SSP1-CH&SPA1; SSP1-CH&SPA3; SSP3-CH&SPA3; SSP4-CH&SPA1; SSP4-CH&SPA3; SSP5-CH&SPA5; SSP0-CH&SPA2. (Illustrative graphic, Infras; Results can be found in the technical report.)

Schmid, N., Oberpriller, Q., Gubler, L., Füssler, J. (2026): Shared Policy Assumptions revisited: A framework for assessing national climate policy pathways. Climatic Change. Vol 179, 108. https://doi.org/10.1007/s10584-026-04200-w 

The SPAs are also described in detail in the technical report on the modeling of greenhouse gas emissions.