Three types of pollution, Pollution reduction, Greenhouse effect, Main absorbing gases, Contributions to the increase of the greenhouse effect, Energy-related activities share, Distribution of greenhouse gas emissions, Mechanisms of the greenhouse effect, Global warming potential GWP, Evolution of greenhouse gas concentrations, Global emissions", Global challenge of unprecedented scale, Depletion of the ozone layer, International negociations, CFC replacement fluids, Acid rain, Decrease of SO2 and NOx emissions