Land Radiative Management Increases Heat Stress in Some Humid Regions

Abstract Heat stress may exceed human physiological limits this century in hot and humid regions. Land radiative management (LRM), a geoengineering strategy that increases surface albedo, aims to reduce heat stress. However, previous work has shown that LRM suppresses rainfall in surrounding regions, drying soils and increasing temperatures. Because soil drying typically reduces wet‐bulb temperatures, a key heat stress metric, one might expect heat stress to decline. Here, we use cloud‐permitting simulations to show that, in sufficiently humid climates, LRM causes wet‐bulb temperatures to rise in surrounding regions, even as soils dry. This occurs because relative humidity in humid regions is largely insensitive to soil drying, resulting in increasing wet‐bulb temperatures with warming. In drier climates, soil drying reduces relative humidity and wet‐bulb temperatures, consistent with prior studies. While hot and humid regions might seem ideal for LRM, it may ultimately increase heat stress.