Projected population exposure to dangerous heat stress around Lake Victoria under a high-end climate change scenario.

Recent global temperature increases and extreme heat events have raised concerns about their impact on health, particularly in vulnerable regions like Africa. This study assesses future heat stress and population exposure in the Lake Victoria region under the high-emission SSP5-8.5 climate change scenario, using a convection-permitting climate model, heat stress indices (humidex and heat index), and high-resolution population projections under the high-emission SSP5-8.5 scenario, interpreted here as the high-end of the climate change signal. Results indicate a substantial increase in the duration of dangerous heat stress. By the end of the century, up to 122 million people, or around 44 $\%$ of the population may experience dangerous heat stress for more than 5 $\%$ of the time annually (i.e. ∼18 days), compared to 1 $\%$ of the population or around 1 million people for the period 2005-2016. Up to 28 $\%$ of the population (∼78 million people) would even experience dangerous heat for 15 $\%$ of the time (i.e. ∼55 days). 66 $\%$ of this increased population exposure can be attributed to the combined effect of increasing temperatures and total population in the region. High heat-risk areas include the northern and southern shores of Lake Victoria and urban areas. The study highlights the need to consider both climate and population dynamics when assessing heat stress, and underscores the urgency of adaptation in the Lake Victoria region.