Digital technologies are indispensable to achieving the Sustainable Development Goals. Yet IT technology has an immense energy requirement for its countless computers and devices, its massive amounts of data and global networks. As a result, more CO2 is released today through digital technologies than all air traffic worldwide, and the energy consumption is increasing due to the rapid spread of digital solutions throughout the world. Every single data transfer consumes energy. Every new data center with its high-performance computers has to be supplied with tons of electricity, and large amounts of energy have to be cooled. Training a single AI model can emit as much carbon as five cars do throughout their lifespans. Deep learning, which trains AI applications, is not only computationally expensive, it is also highly energy intensive and has an immense carbon footprint. Research efforts must be drastically increased in order to find ways to make digital technologies more energy efficient and climate friendly. HPI launched the Clean-IT initiative to present new algorithmic approaches of how digital technologies can be part of the solution of climate crisis – not its accelerator.