This chapter shows the physical causes, and some of the possible consequences of these changes such as climate change, global warming and greenhouse gases, specifically in the context of atmospheric emissions of carbon dioxide, methane and nitrous oxide. Pollution-generated greenhouse gases will impact climate primarily through shortwave and longwave radiation, while aerosols can in addition affect climate through cloud–aerosol interactions. Strategic interventions for reducing emissions from specific anthropogenic activity sector, such as transportation or energy, offer co-benefits to mitigating both climate change and air quality. The chapter describes how the Milankovitch cycles show up in historical evidence about the Earth's climate, and can be used to explain the broad periodicity of the climate changes on the Earth solely in terms of the variation in received solar energy. In general, the aerosol will absorb both down-going solar radiation and up-going terrestrial radiation.