This lecture by the instructor delves into the intricate relationship between energy supply, economics, and the transition towards sustainable practices. Starting with a historical perspective on world population growth and economic activity, the lecture explores the implications of these trends on environmental impact. The concept of IPAT (impact = population x affluence x technology) is discussed, highlighting the role of affluence in driving environmental impact. The lecture also covers the need for decarbonisation, focusing on global CO2 emissions and the imperative to achieve net zero emissions by mid-century. Lessons learned from past economic models and the necessity to move towards a sustainable, less extractive economy are emphasized.