Future Exposure to Heat Stress in Countries Bordering the Great Lakes of Africa: Climate Change and Human Population Growth

Projected increases in temperature extremes have significant implications for humanity and the ecosystems on which we depend. Some of the world's poorest populations reside in the African Great Lakes region (GLR). Poverty increases their vulnerability to current and future heat stress. Fundamentally, exposure to a climate hazard such as heat stress depends on where the people are and where the stress occurs. We used fully coupled, high-resolution (0.25°) Community Earth System Model (CESM) simulations to investigate the impacts of climate change on exposure to heat stress under high warming. Representative Concentration Pathway (RCP) 8.5 was run with spatially explicit population trajectories consistent with Shared Socio-economic Pathways (SSP) 3, regional rivalry/rocky road, and 5, fossil fuel driven. These SSPs are most consistent with high atmospheric CO2. We contrast early and late century human exposure to temperature extremes associated with dangerous health impacts (apparent temperature > 39°C) for nine countries of the GLR. While all countries are projected to experience increases in the number of heat stress days, the greatest increases occur in the north and west, in parts of Kenya, Uganda, and the Democratic Republic of Congo. Nighttime relief diminishes due to 3-8° increases in average minimum temperatures. Country-wide annual heat stress days increase from under 22 days per year (in five countries, <5) to a maximum of 156 days per year. Population exposure to extreme heat stress increases 7-269 fold over current levels. Total population growth as well as rural-urban distribution patterns strongly influence outcomes, but the warming climate is the primary driver of increased heat stress exposure.