Summary Based on a framework of global energy use, investment in different energy pathways and related impacts, historical data and future projections are presented and discussed for key variables, such as human population, economic growth, energy consumption, greenhouse gas emissions and energy-related investments. Essential relationships between variables are determined and evaluated in conjunction with the Kaya equation regarding their individual and combined effects, paying particular attention to the relationship between energy use and economic growth, as well as the effects of energy elasticity, energy intensity and carbon intensity. Further discussed are the impacts of fossil energy use on global climate change, investment trends and conditions for renewable energy transition and decarbonization in integrated assessment frameworks.