Recent temperature records have triggered debate about whether global warming is accelerating. Here, we examine for acceleration and explore possible causes for regional differences using gridded surface temperature data. We find that, global and regional warming is accelerating, and on average, regions with low Human Development Index (HDI) experienced much higher accelerated warming in comparison to regions with high HDI. However, regions of low HDI with a large population experienced slow acceleration due to high local aerosol emissions. Since aerosol negative forcing impacts are short-lived and localized, rapid future reduction of aerosol emissions without a concurrent reduction in GHG emissions could have major compounding impacts. Such a pathway, similar to most 21st century scenarios, could expose a large fraction of the world’s most vulnerable people to sudden warming acceleration and heat stress associated impacts. These results call for targeted climate adaptation strategies directing attention to low-socioeconomic aerosol masked regions.