Air quality model application: First, we estimate, for each city, the total PM2.5 concentrations and the contributions from each of the 12 source sectors. Here, our spatial domain is global, so we refer to these as the "global" simulations. We configure InMAP to use a variable-resolution grid with 2×2.5 degree resolution for the largest cells, each of which are allowed to split into 4 smaller cells up to 6 times recursively, for a minimum grid cell size of 0.031×0.039 degrees (about 3×4 km 2 at the equator). The resulting grid (Figure ) was created by recursively splitting any grid cell containing more than 100,000 people or containing more than 55 million people per square degree in any part of the cell. These 12 simulations (one per source sector), each require ~36 hours on a circa-2019 computer with 32 CPU cores.