World Induced Technical Change Hybrid (WITCH) is a regional integrated assessment model structure to provide normative and qualitative information on the optimal responses of world economies taking place due to climatic damages. It normally deals with the cost-benefit analysis or the optimal responses to climate alleviation policies such as the analysis of cost-effectiveness (Bosetti et al. 2007, 2009). WITCH has a very peculiar game-theoretical model which allows for the modelling of cooperative as well as non-cooperative interactions amongst all developing countries. According to RICE (Rice Integrated model of Climate and the Economy), the non-cooperative interaction is the result of an open-loop Nash game where the 13 regions of the world gets interacted on the environmental concerns in a non­cooperative manner, i. e. greenhouse gas (GHG) emissions, fossil fuels, energy research and development, and on learning-by-doing method in the available renew­able sources (Nordhas and Yang 1996). With this, the investment decision in one particular region significantly affects many other regions’ investment decisions at any point of time. Since the economy of a particular region is based on the lines of Ramsey-Cass-Koopmans optimal growth model and thus the model has been solved numerically by an assumption that the central planner is governing the economy (Barro and Sala-i-Martin 2003).