Model
World Induced Technical Change Hybrid — a global dynamic optimisation model combining a growth model of the economy with a detailed representation of the energy sector and endogenous technical change.
WITCH couples a Ramsey-type optimal growth model with a bottom-up representation of the energy sector. Regions are modelled as strategic players in a game-theoretic setting, so a region's investment decisions take account of the decisions of others — which makes the model well suited to questions about cooperation and free-riding in climate policy.
Technical change is endogenous: the cost of low-carbon technologies falls with cumulative investment in research and with deployment experience, rather than following an exogenous path.
Global, divided into world regions, running to 2100 in five-year steps. The energy sector covers electricity generation, fuel supply and end-use demand; land use and non-CO₂ gases are represented in reduced form.
| Property | Value |
|---|---|
| Model type | Dynamic optimisation, hybrid top-down / bottom-up |
| Solution concept | Cooperative and non-cooperative (Nash) solutions |
| Time horizon | 2005–2100, five-year time steps |
| Technical change | Endogenous — learning by doing and by researching |
| Licence | Open source |