Cities are fundamental to climate change mitigation, and although there is increasing understanding about the relationship between emissions and urban form, so far this relationship has not been used to provide planning advice for urban land use. Here we present the Integrated Urban Complexity model (IUCm), a framework that computes climate-smart urban forms, which are able to cut in half emissions from urban transportation. Furthermore, we show the complex features that go beyond the normal debates about urban sprawl vs. compactness. Our results show how to reinforce fractal hierarchies and population density clusters within climate risk constraints to significantly decrease the energy consumption used for transportation in cities. The new model that we present aims to produce new advice about how cities can combat climate change.