Global population exposure to altitude-related reductions in air density: reproducible analysis and Figure 1 data

This reproducibility package contains the analysis code, exact source geospatial datasets, derived numerical data, validation outputs, and final Figure 1 underlying a global assessment of population exposure to altitude-related reductions in air density. WorldPop 2020 population counts are analysed on their native approximately 30-arc-second resolution and linked pixel by pixel to GMTED2010 mean elevation using geographic cell-centre coordinates. Air-density reduction is calculated from an isothermal pressure-altitude relation and moist-air density at 20 °C and 50% relative humidity, with sensitivity analysis at 37 °C and 100% relative humidity. Country-level estimates use Natural Earth v5.1.1 Admin-0 Countries at 1:10m, assigning population-cell centres to country polygons without redistribution of residual unassigned cells. The archive includes the exact WorldPop and GMTED2010 source rasters used in the analysis, the Natural Earth boundary file, final derived tables, numerical validation checks, and publication-quality Figure 1. Third-party source datasets included in this record retain their original licensing terms: WorldPop 2020 is distributed under CC BY 4.0, while GMTED2010 (USGS) and Natural Earth are public-domain datasets. See SOURCE_DATA_LICENSES.md for details.