Abstract
We applied two metrics, apparent temperature and humidex, to calculate heat stress in both present and future climates. We use an ensemble of CORDEX-Africa simulations to estimate heat stress during a baseline period and at two specific warming levels, 2 and 4 ∘C above pre-industrial. The increase in temperatures and changes to the precipitation distribution under climate change are projected to increase the intensity of heat stress events in Sahelian Africa and introduce new heat stress events in Northern and Central Africa. As the intensity of heat stress increases, it is expected that the use of energy-intensive cooling will increase. The energy system, therefore, will need to be able to supply more energy to power fans or air conditioning units. The cooling demand to turn a heat stress event into a non-heat stress event is computed. This value is then weighted by the population to find the total cooling required to prevent heat stress across the continent. Country-level results indicate that the greatest increases in cooling demand will occur in countries with densely populated regions, most notably Nigeria. Supplying this additional cooling demand will present the greatest challenge to less developed countries like Somalia. We find the least-cost future energy system that meets the projected increase in demand and derive the increase in energy system costs with the TIAM-UCL model. The total increase in energy costs to prevent heat stress is found to be $51bn by 2035 and $487bn by 2076.
Highlights
Heat stress is the inability of a body to cool sufficiently to maintain a stable internal temperature
When global temperatures are 4 ◦C above the historic average (Fig. 1, Supplementary Information (SI) Figure 2), the heat stress changes follow a similar geographic pattern to a + 2 ◦C change but with a higher intensity. This higher intensity is accompanied by an increase in the number of strong heat stress events using the humidex index
The largest increase in variability is around central Africa where the number of heat stress days moving from slight to moderate varies more across the general circulation models (GCMs)-regional climate models (RCMs) pairings
Summary
Heat stress is the inability of a body to cool sufficiently to maintain a stable internal temperature. Methods of mitigating heat stress include evaporative cooling, seeking shade, utilising additional space cooling or altering schedules to allow high intensity work in cooler temperatures (Suzuki-Parker and Kusaka 2016). An increase in the number of heat-related deaths as a result of climate change has been observed (Field et al 2014). The number of heat-related deaths is likely to increase (Dunne et al 2013). There are several different heat stress metrics (Buzan et al 2015), which are dependent on a number of variables including temperature, relative humidity, wind speed and radiation. Tropical regions with high temperatures and humidity are more vulnerable to heat stress than temperate or polar regions (Zhao et al 2015). Coastal cities are susceptible to changes in heat stress as evaporation from the sea increases the water vapour pressure which is a key component of heat stress (Diffenbaugh et al 2007)
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