The policy sciences (politics and applied economics) has developed two models of implementation that are highly relevant for the start of the gigantic COP21 process, covering some 195 states for more than 50 years, at least so it is hoped. The optimistic efficiency theory claims that implementation success is feasible or even probable, once goals are clear and realistic, the means can be identified in reliable technologies and the incentives of the participants altruistically operating. The skeptical failures theory argues that this positive model is a figment of imagination merely. Policies, domestic or international, do not implement themselves. Outcomes are bound to miss objectives and may be unintentional and dysfunctional for the policy. After the natural sciences have researched climate change, the poliy sciences must look at the now unfolding COP21 process.