Abstract : Among global environmental problems, climate change is one of the most serious. According to nearly all scientists, the roots of the problem is related to the accumulation of greenhouse gases (GHG) in the atmosphere and linked with human activities. The global character of this problem turns it into a big challenge. Within a framework of international trade liberalization, the analysis emphasizes the consequences of the interdependencies between economic agents, i.e. States, and of their strategic behaviours – when implementing national environmental policy – on natural environment. Starting with a deliberately conventional model and considering that countries' strategy can be complementary when emitting GHG, we bring new results in many respects and with regard to the existing ones. The thesis includes four chapters. The study highlights the impacts of the nature of the interdependencies between countries i) on the existence and the properties of equilibrium solutions – first, when no country cooperates and then from a globally optimal point of view –, ii) on the sequence of decisions, i.e. the circumstances under which a leader endogenously emerges when initiating its national environmental policy, iii) on profitability and stability of an international environmental agreement (IEA), iv) on the level of participation to an IEA and on the environmental impact of such a cooperation. A distinct feature of this research is to rely on the theorems of supermodular game theory.