Extreme heat is a hazard that typically evolves over periods of days to weeks, affecting large geographical areas (extending over thousands of kilometers) and impacting multiple sectors, including human health, energy consumption and production, industrial plants operations, transportation infrastructure, livestock production, crop yield, forestry, tourism, and labor productivity. Heat waves can compromise public health, reduce productivity and constrain the functionality of infrastructure.
The heat hazard information provided by ThinkHazard! should be considered as preliminary in defining heat hazard in your project area. To further determine the potential risk, a detailed assessment should be undertaken to identify the vulnerability of your project to extreme heat.
Particular consideration should be given to projects located in built-up areas such as cities or harbors since, as compared to rural areas, these areas are subject to an enhanced extreme heat hazard, owing to the urban heat island phenomenon.
Certain projects, such as those concerning individual buildings, or infrastructural components such as transformers in the electricity grid, may require a very fine local-scale extreme heat risk assessment, considering, for instance, indoor versus outdoor heat conditions, or sunny versus shaded locations, involving spatial resolutions down to a few meters.
The indicator used for extreme heat hazard in ThinkHazard! combines temperature and humidity in the Wet Bulb Globe Temperature (WBGT), which is related to human thermal comfort, and which may not necessarily be the most relevant indicator for your project. For instance, if your project concerns energy production, you might rather need an indicator quantifying cooling energy demand (e.g., cooling degree days). This should be sourced from sector specific analyses in the project area, as suggested in some of the links provided below.
You may want to consider the following sectoral vulnerabilities to extreme heat:
• Human health: extreme heat constitutes the single most deadly meteorological calamity, also because extreme heat events often coincide with high levels of atmospheric pollution. Urban populations and those working outdoors in urban or rural areas are most vulnerable. Further guidance is provided by WMO and WHO (2015) Heatwaves and Health: Guidance on Warning-System Development, http://www.who.int/globalchange/publications/heatwaves-health-guidance/en/
• Labor productivity may be impacted by extreme heat, especially in the case of outdoor workers, or workers in poorly cooled or ventilated buildings. Agricultural, manufacturing, and construction workers are among the most vulnerable groups to outdoor heat. The WBGT is an appropriate metric in the context of labor productivity, although the assessment of indoor exposure to extreme heat could benefit from dedicated local estimates, done with commercially available WBGT measuring instruments.
• Energy production, especially electrical energy production, is particularly vulnerable, given that the infrastructure for production and transmission (e.g., transformers) of electrical energy may experience breakdowns in periods of extreme heat. Moreover, periods of extreme heat often go together with an increased electricity demand peak for active building cooling, and at the same time coincide with an increased difficulty in obtaining sufficient cooling water for thermal power generation during very hot conditions.
• Renewable energy production, in particular solar-based (photovoltaic (PV) panels and concentrating solar power (CSP) plants) may see their output reduced in periods of high temperature. In the case of PV modules, one should account for the temperature dependent electrical efficiency, and implement mitigating measures, such as installing PV panels a few inches above roofs to allow convective air flow to cool the panels.
• Industrial plants may have difficulties cooling, especially those that depend on natural cooling from wind. In addition, heat-induced energy production may decrease and negatively affect the operations at industrial plants.
• Transport infrastructure is also sensitive to extreme heat. Railway operations may be adversely affected by railway track buckling, material fatigue, and overheating of equipment. Road pavements may get damaged, and car tires may experience failure at high temperatures. Aviation may face damage to the runway surface, and take-off weight limitations during hot periods.
• Crop yield may be adversely affected by heat, especially if the heat is accompanied by drought. Under these conditions of combined heat and drought, there is an enhanced risk of forest fires, heat-induced tree mortality and decline in tree growth rates, impacting forestry projects. Dedicated species-specific growth curves, which express plant growth response as a function of temperature, can be used to estimate impact on forestry projects.
• Livestock production may become compromised during periods of extreme heat, especially intensive dairy cattle systems, owing to decreased fertility and increased mortality, reduced milk production and associated income losses. Poultry and pigs are also sensitive to extreme heat.
• In certain areas Summer tourism may undergo negative consequences of extreme heat, though other (cooler) areas might benefit from it. So-called ‘tourism climate indices’ have been established to evaluate this.
Apart from these sector-based considerations, be aware of the fact that your project’s vulnerability to extreme heat hazard may also arise from indirect sectoral impacts. For instance, an industrial production unit may see its operations compromised not only because of local heat stress conditions (affecting labor productivity or component failure), but also because of interrupted transportation and/or energy producing infrastructure affecting its supply lines.
Extreme heat hazard often occurs together with drought (water scarcity), information of which is also available on the ThinkHazard! platform. Heat and drought combined may reinforce each other’s impacts, e.g., during an extreme heat episode, an industrial plant may require enhanced cooling, but a concurring drought might limit the availability of cooling water.
• WMO and WHO 2015. Heatwaves and Health: Guidance on Warning-System Development, http://www.who.int/globalchange/publications/heatwaves-health-guidance/en/
• Queensland University of Technology 2010. Impacts and adaptation response of infrastructure and communities to heatwaves: the southern Australian experience of 2009, report for the National Climate Change Adaptation Research Facility, Gold Coast, Australia; https://www.nccarf.edu.au/publications/impacts-and-adaptation-responses-infrastructure-and-communities-heatwaves
• Information regarding ‘Tourism Climate Indices’ can be found in the following: https://earth-perspectives.springeropen.com/articles/10.1186/s40322-016-0034-y.