Heat Exposure in Informal Settlements in Nairobi, Kenya

Heat exposure, one of the deadliest climate-related impacts and a growing concern in a warming climate, is exacerbated by urban-rural differences in microclimate, also known as the urban heat island effect. The urban heat island effect is well studied around the world, mostly looking at differences between temperature conditions within an urban area and the surrounding rural areas. Recent work has urged scientists to take into account the heterogeneity within cities (for example, the local climate zone or LCZ classification by Stewart and Oke 2012), as some microclimates may be several degrees hotter than others. Nairobi, Kenya exhibits a wide variety of microclimates brought about by heterogeneous surfaces, from paved roads and high-rise buildings interspersed with low vegetation in the central business district, to large neighborhoods of informal settlements or ‘slums’, characterized by dense, metal housing, little vegetation, and limited access to government services. To investigate how heat exposure differs within Nairobi, we deployed a high density observation network in 2015/2016 to examine summertime temperature and humidity. We show how temperature, humidity and heat index differ in several informal settlements, including Kibera, the largest slum neighborhood in Africa. We also relate these changes to surface properties such as satellite-derived albedo and NDVI. Understanding the existence of micro-climates within the urban setting can have important implications for the disaster management and public health spheres by creating opportunities for more targeted interventions to reduce the effects of heat exposure now and in a warmer climate.