As described above, high-resolution emissions estimates are important for urban-scale analysis. The fourth point is that downscaling existing inventories using spatial surrogates can only yield improvements up to a certain point. The global CEDS inventory used here is mainly based on national emissions estimates that are themselves downscaled to a 0.5×0.5 degree grid using mainly population density estimates. This can lead to spatial misallocations that cannot be fixed by further downscaling. For example, using the national-population-based spatial allocation method above in a country with substantial residential coal emissions could allocate a plurality of those emissions to the cosmopolitan capital city, where in reality there were relatively few residential coal emissions owing to the capital's relatively high level of affluence. The next generation of global emissions inventories may benefit from the emergence of new streams of relevant data-for example from smart phones and satellites-in combination with local expertise facilitated by networks of cities like C40.