The latest Intergovernmental Panel on Climate Change (IPCC) Report (AR6) has signalled a code red for humanity, and an urgent need to respond to the climate emergency. This chapter begins by setting out the scientific basis for climate change and the economic, social and health threats it poses to our collective future. It then looks at the significant role the built environment plays in this emergency, what percentage of greenhouse gas emissions buildings are responsible for and at what point in a building’s lifecycle do these emerge? Finally, it captures a high-level summary of ongoing action in the built environment, charting existing pathways towards ‘net zero’ before outlining some of the challenges that need to be overcome in our race to a net zero carbon-built environment.