This lecture discusses the urgent need for decarbonisation in the context of energy supply, economics, and transition. It covers the global efforts required to limit warming to 1.5°C or 2°C, the decarbonisation of Switzerland, the risks associated with unburnable carbon assets, and the impact on investments in fossil fuel companies. The instructor emphasizes the importance of transitioning to carbon-free energy by 2050, the risks of stranded assets, and the implications for the global economy and climate policies.