This paper discusses the global warming, its causes and consequences. The paper assesses the impact of the polices adopted by the UN organizations including the Intergovernmental Panel on Climate Change (IPCC) to mitigate global warming, and the consequences following failure of the Kyoto Protocol to mitigate global warming. The key issues discussed here include the ineffectiveness of the UN climate change policies and the role of urbanization in greenhouse gases emissions mitigation. It is evident that the UN efforts to combat climate change through mitigation of global warming are ineffective due to many issues. These are summarised in the increasing causes of urbanization and development of "megacities" around the world, and particularly in the less developed nations due to the current global polices and the economic model which favour urbanization.