Digital technologies are indispensable for achieving sustainable development goals and reducing carbon emissions in many sectors. Yet, computer systems themselves have an immense energy requirement for their countless devices, data centres, applications and global networks. With COVID-19, the shift to digital in living, learning and earning has raised the spectre of digital harms and brought us closer to the time when digitalisation will become an increasing social and climate hazard. Since digitalisation has many important benefits, the G20 can be the first to acknowledge the issue of its rising global footprint and take pioneering steps towards global agreements on effective actions to counter it. The G20 can lead international agreements on common standards to measure energy consumption and propose a global “clean-IT” label. Furthermore, global awareness campaigns for policy makers, and in education and research institutions must be initiated beginning with the G20 countries to increase funding for research activities in this urgently needed, yet barely recognised field. “Sustainability by Design” has to be the new paradigm in digital engineering education, research and application worldwide.