Extreme heat Hazard level: Medium ?

In the area you have selected (Hong Kong, SAR) extreme heat hazard is classified as medium based on modeled heat information currently available to this tool. This means that there is more than a 25% chance that at least one period of prolonged exposure to extreme heat, resulting in heat stress, will occur in the next five years. Project planning decisions, project design, and construction methods should take into account the level of extreme hazard. The following is a list of recommendations that could be followed in different phases of the project to help reduce the risk to your project. Please note that these recommendations are generic and not project-specific.

According to the most recent assessment report of the Intergovernmental panel on Climate Change (IPCC, 2013), continued emissions of greenhouse gases will cause further warming, and it is virtually certain that there will be more frequent hot temperature extremes over most land areas during the next fifty years. Warming will not be regionally uniform. In the area you have selected, the temperature increase in the next fifty years will be slightly lower than the worldwide average, but still significant. It would be prudent to design projects in this area to be robust to global warming in the long-term.

Recommendations

• VULNERABILITY ASSESSMENT: The high-level information available in ThinkHazard! indicates the presence of extreme heat hazard in your project area. Before committing significant resources to this issue, you should further evaluate if your project is vulnerable to extreme heat and whether a more detailed assessment and/or intervention should be considered. More information
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  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.

  Further resources: • 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.

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• SEEK INFORMATION: Obtain pre-existing extreme heat hazard information. ThinkHazard! predominantly uses global datasets, therefore for more detailed project planning you should determine the availability of pre-existing local extreme heat hazard information to check whether your project is indeed located in regions prone to extreme heat. In this respect, it should be noted that large built-up areas such as cities or harbors are more likely to experience excess heat than rural areas, because of the urban heat island phenomenon. More information
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  As a first step towards obtaining local extreme heat hazard information for your project area, you should seek information from your National or Regional Meteorological Agencies, which often keep records and statistics about the occurrence of extreme heat.

  In case your project is located in a built-up environment (city, harbor, or large industrial area), check for the availability of local heat maps, including a representation of the urban heat island phenomenon. Urban areas are generally warmer than their rural surroundings because of the differing thermal characteristics of buildings and paved surfaces compared to natural surfaces. While the resulting temperature difference is on average of a few °C, temperatures in urban or harbor areas may be higher than rural values by up to 7-8°C (12-14°F) and more at night-time under favorable conditions. These higher urban temperatures are not contained in the assessment of extreme heat hazard in the ThinkHazard! platform. Also, information gathered from the National Meteorological Service will most likely not contain urban effects, as their observational procedures typically avoid urban areas. The level of spatial detail in a local heat map should ideally be of the order of a few hundred meters or better, and allow to identify so-called hot-spot zones.

  Evaluate whether local regulations exist for extreme heat, such as national or regional definitions used to define heat wave episodes. There is no generally accepted definition of heat wave, the definition differing between countries and economic sectors. Evaluate whether local regulations include heat-health action plans, and health and safety regulations such as compulsory labor rest times in case of extreme heat. In case of infrastructure projects, verify whether local regulations exist concerning building codes (e.g., containing reference to climate-resilient building practice or obligations, such as green roofs), resistance to heat of materials used in transportation infrastructure (e.g., railway buckling risk as a result of high temperatures, road asphalt melting temperature thresholds, maximum load capacity of devices cooling large IT infrastructure).

  When collecting local information, make sure to consider the right type of indicator for your sector of interest. For projects involving potential health or labor productivity issues, a number of ‘human thermal comfort’ indicators are available. For the energy sector, an indicator based on the concept of ‘cooling degree days’ may be more relevant. Crop yield will be governed by other indicators, involving temperature thresholds that may vary by crop type, and that may need to be combined with an indicator of drought status.

  Conduct interviews with sectoral organizations regarding local vulnerability, based on past experience. For extreme heat hazard, consider the following organizations:

  • public health authorities • labor associations • transportation organizations (road, rail, water, air) • the agricultural sector • the electricity producing/distributing sector • industrial plant operators

  Try to obtain evidence of previous extreme heat events. If available, reports on previous extreme heat events may be very valuable, especially when providing recommendations and measures to cope with extreme heat.

  It is also recommended to try and find examples of good practice in other countries, regions, and locations that exhibit a comparable level of extreme heat hazard, and of which the project exhibits similar characteristics (e.g., similar sector, same infrastructural or environmental characteristics). Indeed, the issues you may encounter when considering extreme heat hazard for your project could have been dealt with previously elsewhere, and it may be very efficient to learn from that. Sectoral or city networks play a crucial role in accelerating the diffusion of good ideas and best practices, both domestically and internationally. Examples of such networks are:

  • REN21, the Global Renewable Energy Network (www.ren21.net/about-ren21/about-us/); • ICLEI, Local Governments for Sustainability, a global network of more than 1,500 cities, towns and regions (www.iclei.org); • IUC, the International Union of Railways, representing the railway industry (www.uic.org/).

  In case your project concerns (or is located within) the built environment, a relevant starting point for obtaining examples of good practice is the Second Assessment Report on Climate Change and Cities (ARC3.2), published by the Urban Climate Change Research Network (UCCRN). In particular, the cases described in the ‘Case Study Docking Station’ (http://uccrn.org/casestudies/), which may be queried by geographic location or climate zone, provide very relevant information.

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• PROFESSIONAL GUIDANCE: Consultation with engineering and climate impact assessment professionals will provide a more detailed understanding of the risk posed to your asset by extreme heat. The level of guidance required will depend upon the level of hazard present, the vulnerability of the asset and local legislation that might apply. More information
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  Professional guidance ranges from informal advice from local experts to a detailed and comprehensive site-specific heat risk assessment. The required level of consultation will depend on the vulnerability of your project, and the anticipated level of extreme heat hazard.

  As an initial step, obtain informal advice from local knowledge centers (research centers, universities), to gain a better understanding of extreme heat hazard. Researchers and academics, active in engineering and/or climate impact assessments and with expertise in your location of interest, may have an intricate knowledge of extreme heat hazard, and be able to recommend key datasets and information available in your project area.

  A more detailed understanding of extreme heat hazard in your project area can be obtained from a heat risk appraisal. This will give a more detailed view of extreme heat risk than provided by the ThinkHazard! platform, while still providing a relatively broad view of heat risk. Such studies are typically performed remotely, attempting to provide a generic assessment of heat risk, by integrating available sector-specific information (e.g., considering cooling degree days in case of the energy sector, or crop type-specific temperature thresholds). At this level, coarse-scale modeling can be considered, including urban heat risk mapping in case a project happens to be located in an urban environment. A heat risk appraisal will highlight key areas where a more detailed study may be required.

  A site-specific heat risk assessment constitutes the most detailed appraisal of heat risk at the project location and the impact of extreme heat on the heat-sensitive components of critical infrastructure. Such assessments can also provide information regarding the design process to minimize heat risk, and the appropriate level of adaptation required. Site-specific heat risk assessments should be conducted by consultants with a proven expertise (ask for references) in the domain of climate impact assessment, and in the considered sector. Consultants should be able to demonstrate their expertise in undertaking and delivering heat risk appraisal assessments and have experience in the project area, including regarding available data and information, and local legislation. They should also be expert in assessing the impact of future climate projections, considering time horizons that are appropriate for the concerned project.

  Often, a site-specific assessment will rely heavily on detailed computational impact modeling, such as, e.g., building energy modeling or crop yield modeling. Such models can also be used to simulate scenarios for adaptation, which may suggest solutions for combating extreme heat hazard. For instance, certain building energy models allow calculating the impact of adaptive measures against heat stress, such as solar blinds, enhanced ventilation, or shading.

  Further information: • Building energy assessment through modeling, using the EnergyPlus model http://energy-models.com/software/energyplus • Overview of crop yield modeling: https://en.wikipedia.org/wiki/Crop_simulation_model • WMO and WHO, 2015. Heatwaves and Health: Guidance on Warning-System Development. World Meteorological Organization (WMO) and World Health Organization (WHO). WMO-No. 1142. Available from http://www.who.int/globalchange/publications/heatwaves-health-guidance/en/.

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• MONITORING AND FORECASTING: Identify extreme heat monitoring and forecasting systems. These are designed to provide communities with advanced warning of extreme heat based largely on information contained in weather forecasts, complemented with temperature monitoring. They can be used to trigger protocols (e.g., the deployment of heat-health action and emergency response plans) to mitigate against the effects of extreme heat. More information
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  Heat early warning systems are instruments to prevent negative impacts during heat waves. If sufficient warning can be given, then mitigation procedures can be implemented. Heat early warning systems are based on weather forecasts, which are used to predict situations associated with adverse heat-related impacts. Heat early warning systems are generally triggered by the predicted exceedance of given temperature (or thermal index) thresholds. The efficient communication of the heat wave and prevention responses constitutes an important component. Most heat early warning systems target the health of the general population, attempting to induce behavioral changes, ensuring operational status of emergency systems, and to adequately provide information to vulnerable groups. For a description of intervention strategies, WMO/WHO guidance at http://www.who.int/globalchange/publications/heatwaves-health-guidance/en/.

  Early warning systems may also be relevant for other sectors than health, allowing e.g. transport, energy production or industrial operators to trigger timely action in reducing the effects of hot weather extremes on the concerned sector. However, for sectors other than health, it might be worthwhile to consider alternative heat stress indicators. For instance, in the case of energy producing plants, an indicator based on the concept of cooling degree days may be relevant.

  If your project provides a critical service (energy production and distribution, railway operations), consider implementing measures to ensure the project can continue to function in case of extreme heat, such as local cooling measures (such as spraying water on sensitive sections of railway tracks to locally cool and avoid buckling), or having an alternative energy supply system (e.g., in hospitals).

  Find out whether a heat early warning system exists for your area. In some cases, it is feasible to establish a real-time connection to the heat early warning system, through receipt of text messages or emails from the system’s operator when critical thresholds of temperature or thermal indices are reached. Ensure that any received extreme heat forecast or warning can be rapidly and clearly communicated to all staff and project beneficiaries at the project location, and develop protocols that define actions to be taken when a warning is received. For critical or networked assets, protocols should warn of possible service interruption and highlight that backup asset services may be required.

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• INTERDEPENDENCY: Consider vulnerability of other assets within the project's dependency network: If your project is interdependent with other projects, it is important to assess the vulnerability of the entire network if the service provided is critical. More information
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  When planning a project in whatever sector or geographic area, be aware of possible inter-sectoral effects, which are numerous and can exhibit a cascading character, with heat-related failures in one sector cascading down to other sectors.

  This is related to a high degree of potential interdependency of sectors in which different projects may be situated. Some examples (non-exhaustive) of inter-sectoral impacts initiated by extreme heat are given below:

  • Extreme heat causing transport system failure (e.g., overheating trains) can affect labor productivity by hampering commuters from going to their work. A reduced transport capacity may also affect the delivery of goods to their destination, which may also reduce productivity. Railway systems, constituting a sensitive group within the transport sector, may cool tracks by spraying water on them, and improve the stability and strength of railway tracks (for instance by using concrete instead of timber sleepers supporting the tracks) and use materials that limit shrink/swell of the trackbed. Air conditioning systems in trains may benefit from improved maintenance or by upgrading to systems with a higher heat tolerance to prevent early shut-off. Roads can be made more resilient to extreme heat hazard by using high-grade heat-resistant asphalt (to avoid excessive softening of asphalt under heat stress). • Outdoor workers experiencing extreme heat stress may see their productivity reduced. In the case of agricultural workers, this may affect food security in the project area, which may already be under pressure from the direct impact of heat stress on crop yield. Reduced food production may further induce an income loss for the agricultural workers. Labor productivity of outdoor workers may benefit from new work practices (e.g., adapted working hours during the cooler hours of the day), or through the provision of shade to avoid heat stress. Indoor workers’ productivity will benefit from improved building design (improved insulation, enhanced thermal mass, solar blinds, using nocturnal ‘flush’ ventilation as a means of passive cooling). Also, natural shading by trees may considerably reduce the heat load on buildings. • Heat-related failure of energy production facilities may lead to reduced productivity at industrial production plants. It may also impair the operation of building cooling systems, resulting in negative health effects and affecting the operational capacity of critical infrastructure such as hospitals. It may affect transportation by disrupting power to common systems such as traffic lights. Cooling of energy producing plants to minimize the risk of failure may be achieved by technological means, considering, e.g., relatively simple and low-cost options such as exploiting non-traditional water sources and re-using process water, up to measures such as installing dry cooling towers, heat pipe exchangers, and regenerative cooling. The electricity distribution network may reduce overheating by increasing system capacity, increasing tension in the power line to reduce sag, and by adding external coolers to transformers. • Many critical services, including the provision of health care, are highly sensitive to the ways in which climate extremes disrupt buildings, transportation, and electricity. Making urban infrastructure more resilient will lead to better health outcomes during future heat events. Also, essential services that depend on the stable supply of electricity (hospitals, airports) may want to consider the installation of stand-alone generators capable of operating during prolonged power outage. • Heat events also put water resources under strain, affecting not only consumers of water consumption or power but industries reliant on water for transport or irrigation. For example, if drinking water is taken from a canal, the enhanced demand for water may compromise transport by cargo vessels on that canal. Conversely, irrigation may reduce water for drinking supply. In general, hot and dry periods lead to an enhanced competition for water resources.

  Be aware of event chains that may lead to system collapse. Imagine an extreme heat episode, combined with drought. Energy provision gets compromised because of a lack of cooling water, and therefore active building cooling (air conditioning) ceases, perhaps also in hospitals (unless there is a provision of backup electricity that withstands high temperatures). At the same time, problems in the transportation network hamper the transport of heat stroke victims to hospitals.

  During extreme heat events, negative feedback cycles may develop, exposing high levels of sensitivity across systems to changes in operating conditions. For instance, in case an electricity system operates with little spare capacity or redundancy, it will have a consequent lack of resilience to an unexpected perturbation such as a heat wave, during which demand across the grid is higher than normal. The shutdown of only a small part of the electricity grid (owing e.g. to heat-related asset failures such as that occurring in transformers under excessive heat stress), together with reduced transmission efficiency, may lead to outages of major transmission lines, load shedding and, ultimately, power blackouts.

  Scenario testing should be undertaken for potentially hotter and more prolonged events on service continuity by infrastructure and essential service providers. Such analysis needs to be system wide to explicitly account for cascading effects. To gain insight into heat-related chains of events that may lead to system collapse, see a report describing the impact of the severe 2009 heat wave that shook Southern Australia, and containing the description of a range of response strategies that were formulated in the aftermath: 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.

  Finally, it should be noted that certain solutions for extreme heat mitigation may also be beneficial for other hazard types and assets. For instance, green infrastructure (including the use of green roofs, porous pavements, and urban parks) not only reduces heat stress (by evaporative cooling, and by providing shade), but it can also improve storm water management and thus reduce flood risk in cities. By allowing rainwater to infiltrate into the soil, green infrastructure is also a relevant measure for combating drought in built-up areas. Finally, green infrastructure comes with a host of other co-benefits such as greenhouse gas mitigation, and an improved and more pleasant environment for city dwellers, including enhanced social benefits.

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• HEAT MANAGEMENT: Your project or development should consider heat management measures appropriate to your sector of operation, for example, technological adaptation, building design, or changing working practices. More information
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  Appropriate measures to manage excessive heat situations depend on the sector considered.

  • Livestock productivity may benefit from improved ventilation and housing conditions, and from genetic approaches for breeds that have a better resilience against heat stress. Grazing animals will benefit from the provision of shade. • In agricultural projects, one ought to consider technological adaptation responses, such as stress-tolerant crop varieties, irrigation, and enhanced monitoring systems. This sector may also benefit from heat early warning systems. Forestry may benefit from an improved wildfire management. • Labor productivity may benefit from new work practices (e.g., adapted working hours during the cooler hours of the day) to avoid heat stress among both indoor and outdoor workers. Indoor workers’ productivity will benefit from improved building design (improved insulation, enhanced thermal mass, solar blinds, using nocturnal ‘flush’ ventilation as a means of passive cooling). Also, natural shading by e.g. trees may considerably reduce the heat load on buildings. • During extreme heat events, indoor thermal comfort can obviously be improved by using active mechanical cooling (air conditioning). However, apart from contributing to enhanced greenhouse gas emissions, such devices shed heat to the outdoor air, thus increasing the urban heat island effect. Finally, air conditioning may be unreliable during heat events, in case electrical energy production or distribution gets compromised. • Railway systems, which within the transport sector is a very sensitive group, may cool tracks by spraying water on them, and improve the stability and strength of railway tracks (e.g., by using concrete instead of timber sleepers supporting the tracks) and materials to prevent shrink/swell of the trackbed. Air conditioning systems in trains may benefit from improved maintenance or by upgrading to systems with a higher heat tolerance to prevent early shut-off. • Roads can be made more resilient to extreme heat hazard by using high-grade heat-resistant asphalt (to avoid excessive softening of asphalt under heat stress). • Cooling of energy producing plants may be achieved by technological means, considering, e.g., relatively simple and low-cost options such as exploiting non-traditional water sources and re-using process water, to measures such as installing dry cooling towers, heat pipe exchangers, and regenerative cooling. The electricity distribution network may reduce overheating by increasing system capacity, increasing tension in the power line to reduce sag, and by adding external coolers to transformers. • Solar energy production by photovoltaic panels may reduce output losses passively by natural air flows or actively by forced air or liquid coolants. • Overall, essential services that depend on the stable supply of electricity (hospitals, airports) may want to consider the installation of stand-alone generators capable of operating during prolonged power outage.

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• AVOID INCREASING HAZARD: Built infrastructure may alter heat hazard. Constructing a significant piece of infrastructure can significantly alter the thermal properties of the area, generally inducing higher temperatures. Any newly built infrastructure covering large enough areas (e.g., new city quarter or harbor zone) should be undertaken with consideration as to how this will influence the local microclimate. More information
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  The thermal properties of urban construction materials, together with the spatial layout of built-up areas, induce the urban heat island effect, which is marked by overall higher surface and air temperatures in urban areas, compared to their rural surroundings. This phenomenon is particularly strong during the night, when a city may be 7-8°C (12-14°F) warmer than neighboring rural areas. It should be noted that other types of built-up areas, such as extensive industrial or harbor areas, may also exhibit a pronounced heat island effect.

  Urban (or, more generally, built-up) density and form do have an impact on the overall intensity of the heat island effect. Therefore, when your project considers the construction of a significant piece of infrastructure, it is important to account for the impact of the project on altering the local microclimatic conditions, and any related extreme hazard.

  As general (but very rough) guidance, modified surface characteristics affect the overlying atmosphere up to a height equivalent to 1% of the horizontal extent of the project area. For example, in the case of a new industrial facility extending over an area with a diameter of, say, one kilometer, the atmosphere will likely be affected up to a height of approximately 10 m. This means that, e.g., a piece of critical infrastructure such as a transformer in the project area could have its operation adversely affected by heat whenever it is located below 10 m. (Depending on the atmospheric conditions, and on the roughness structure of the project, this height may be less or more – again, the numerical values given here are at best rough indications.)

  Climate adaptive options for the built environment that can help to avoid increasing heat hazard, may be sub-divided into three categories: gray, green, and soft measures.

  • Grey measures are technological and construction material (and infrastructural outlay) based measures. Examples include cooling through enhanced design, such as the use of insulation, solar blinds on exposed buildings, the creation of natural ventilation and of shade. Selecting construction materials and reflective coatings (e.g., white roofs) can improve building performance by managing heat exchange at the surface. Modifying the form and layout of buildings and urban districts can provide cooling and ventilation that reduce energy use and allow citizens to cope with higher temperatures and more intense runoff. Active cooling by air conditioning devices also constitutes a gray measure, though this option should be considered with care, as it may lead to enhanced greenhouse gas emissions, and to an enhanced urban heat island effect through the shedding of heat to the outdoor environment.

  • Green measures rely on vegetation as an adaptive measure. Investing in urban ecosystems and green infrastructure can provide cost-effective, nature-based solutions for adapting to climate extremes while also creating opportunities to increase social equity, green economies, and sustainable urban development. Increasing the vegetative cover in a built-up environment can simultaneously lower outdoor temperatures, building cooling demand, runoff, and pollution while sequestering carbon. When boosting green infrastructure, it is important to implement an appropriate watering scheme to ensure the infrastructure’s sustainability. An important issue when considering green measures is that, while such measures can be very effective, sustainable, and yielding a host of co-benefits; their impact generally is very local. For instance, green roofing can have a large impact on the building it covers but generally has a modest impact only on the overall urban heat island. And urban parks, while very effectively reducing heat stress, only do so within the park’s boundaries, the effect being lost quickly beyond these boundaries.

  • Soft measures target awareness, and organizational and behavioral change to better cope with extreme heat hazard. General awareness raising is instrumental in the deployment of soft measures. Warning systems, heat action plans, and the establishment of appropriate institutional structures are also part of it, as are the preparedness of the health and social care system, and the adaptation of building codes. The development of heat-health action plans is an example of a soft measure.

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