Addressing the Overlooked Impact of Heat Stress in Informal Settlements

The year 2023 marked the hottest year on record, and the rising levels of humidity have further exacerbated the impact of heat on our lives and livelihoods. The dangerous combination of heat and humidity has pushed us dangerously close to the upper limits of what human beings can endure. However, the underestimation of heat stress in cities due to poor weather station coverage across the tropics highlights the flawed global climate change assessments that overlook the local impacts on vulnerable communities.

Informal settlements, commonly referred to as “slums,” primarily concentrated in tropical Asia and Africa, face the brunt of climate change. These settlements, lacking proper infrastructure and services, are highly vulnerable to the increasing levels of humid heat. With rapid urbanization outpacing planned development, the growth of informal settlements has become a pressing issue. Currently, over 1 billion people live in these settlements, and the United Nations estimates that this number will rise to 3 billion over the next three decades.

The majority of informal settlements are situated in the tropics, where temperature and humidity levels are consistently high throughout the year. However, due to their locations, these settlements are often not adequately monitored by weather stations. Most of the world’s population is more than 25km away from a weather station, resulting in limited data on temperature and humidity in urban areas. This lack of monitoring is especially prevalent in the tropics, where the highest concentration of informal settlements exists.

Individuals experience heat stress on a local scale, and the sparse weather station networks fail to capture this localized impact. To shed light on this issue, our research compiled local climate monitoring data from informal settlements across seven tropical countries. Comparing these data to measurements from the nearest weather station, we discovered a severe underestimation of heat stress levels experienced by people in their homes and communities. This discrepancy points to the likelihood that global climate assessments and projections also underestimate the local-scale impacts of climate change.

During heatwaves, conventional advice such as staying indoors and drinking plenty of water may worsen the situation for residents of informal settlements. In these settlements, many households lack proper ventilation and insulation, making the indoor environment even more unbearable during extreme heat. The scarce availability of air conditioning further exacerbates the health risks faced by these communities. Adding to the problem, early-warning systems that could alert residents of dangerous levels of heat are also lacking. Only half the world’s countries have such systems in place, leaving vulnerable communities without the necessary information and support to mitigate heat stress.

The implications of inadequate climate monitoring and the underestimation of heat stress are dire for the health and well-being of individuals, societies, and economies. Developing countries’ meteorological institutes require urgent support to enhance climate monitoring and improve early-warning systems. It is crucial that governments, development banks, and NGOs capitalize on this opportunity to integrate informal settlements into new monitoring networks. Moreover, addressing inequalities in resources and adaptive capacities is paramount. Initiatives like urban greening and improved housing show promise in reducing urban heat and should be prioritized in adaptation efforts. Failing to take action means leaving vulnerable communities with no choice but to resort to climate-related migration, further uprooting their lives and risking their well-being.

The damaging impact of heat stress in informal settlements cannot be overlooked. It is imperative that climate change assessments, monitoring systems, and adaptation efforts take into account the unique challenges faced by vulnerable communities in the tropics. By recognizing and addressing the disproportionate exposure to heat stress, we can work towards a more equitable and resilient future for all.