Thesis: This dissertation investigates the economic mechanisms underlying the transition to clean technologies and examines policy approaches to achieve the socially optimal path. It studies various policy measures aiming to deal with climate change, such as adaptation and taxation of non-renewable resources. Furthermore, it examines the policy instruments that target increasing the use of efficient technologies and identifies cases in which the policy reaches its objectives or not. It also analyzes the role of heterogeneity in society on agents' willingness to support a pollution tax. The first chapter studies the energy transition by using an optimal growth model in which non-renewable and renewable natural resources are imperfect substitutes in providing energy services necessary for production. The second chapter studies the role of adaptation policy on the transition to a low­ carbon economy. lt incorporates adaptation policy into the problem of optimal non-renewable resource extraction with pollution externalities, by focusing on the capital nature of adaptation measures. The third chapter focuses on the problem of adopting new technologies in a micro-economic framework. lt studies the behavior of firms when they face a decision to invest either in a cheap but inefficient production capacity or in an expensive but efficient one, by taking into account the presence of a financial constraint. The fourth and last chapter investigates the distributional impacts of a pollution tax by considering a society in which wealth is distributed heterogeneously among households.