Efficient, smart, environmentally friendly? Artificial Intelligence (AI) is often hailed as a solution to the major challenges of our time, including the fight against climate change. But behind this shining vision of the future lies a blind spot: AI consumes enormous amounts of energy, generates CO₂ emissions, and remains largely opaque in terms of its environmental footprint. Few people are aware that the operation of AI systems already leaves a measurable and rapidly growing ecological footprint worldwide. Yet reliable data, suitable measurement methods, and binding standards to assess this impact are still lacking. One thing is clear: anyone who wants to design and use AI responsibly must also consider its sustainability. This article explains why AI policy must always also be sustainability policy. What needs to change to make that possible?