HEAT WAVES FOR CITY MANAGERS AND ELECTED OFFICIALS AND PROPERTY MANAGERS

Heat waves represent a significant and growing threat to human health, well-being, productivity, and urban infrastructure worldwide. As city managers, elected officials, and property managers, understanding these phenomena and implementing effective strategies is paramount to building resilient urban communities. ### I. Understanding Heat Waves: A Growing Threat Heat waves are periods, usually lasting several days, with **temperatures significantly higher than average or maximum values observed in the past during the same dates**. They are characterized by abnormally warm conditions and prolonged exposure. Climate change is projected to increase their **frequency, intensity, duration, and spatial extent**. Some regions have already seen a remarkable growth in climate-related extreme events, including heat waves. For example, studies project that extreme heat events in European capitals will become a significant threat in the near and distant future, extending beyond traditionally exposed areas like the Mediterranean and Iberian Peninsula. The scientific definition of a heat wave can vary, but a common meteorological definition for a terrestrial heat wave is **three or more consecutive days where the maximum temperature is over the 90th percentile for a particular location at a particular time**. However, specific thresholds often depend on local factors like population acclimatization, age, health preconditions, and other meteorological variables such as humidity and wind speed. Different countries and cities have adopted their own criteria, often based on the relationship between temperature and excess mortality, such as France using the 98th or 99.5th percentile temperature values. ### II. Impacts of Heat Waves on Cities The impact of heat waves is particularly pronounced in urban areas due to several compounding factors: * **Urban Heat Island (UHI) Effect:** Cities are typically much warmer than their surrounding rural environments, a phenomenon known as the Urban Heat Island effect. This is exacerbated by the built environment's materials, lack of green spaces, and **anthropogenic heat emissions** from buildings (e.g., air conditioning units) and vehicles. This additional urban heat increases risks during heat waves. * **Health Impacts:** Heat waves cause elevated rates of illness and death due to heat stress. Specific health effects include: * **Direct Heat-Related Illnesses:** Heat cramps, heat exhaustion, and life-threatening heatstroke. * **Increased Mortality:** Severe heat waves have been responsible for significant excess deaths, such as nearly 800 deaths in Chicago in 1995, approximately 14,800 excess deaths in France in August 2003, and 1906 excess deaths in Lisbon during a 1981 heat wave. These deaths often occur in hospitals, homes, and nursing homes. * **Vulnerable Populations:** Certain segments of the population are more at risk, including the elderly, socially isolated individuals, those with pre-existing medical conditions (psychiatric, pulmonary, cardiovascular illnesses), young children, and people working outdoors. Poorly maintained housing stock and higher poverty rates also contribute to vulnerability. * **Morbidity:** Heat waves can increase hospital admissions for cardiovascular and respiratory diseases and adverse birth outcomes. Loss of well-being due to restrictions in daily activities and symptoms like fatigue, cramps, decreased alertness, and cognitive function are also reported. * **Economic and Infrastructure Impacts:** * **Energy and Utility Strain:** Heat waves significantly increase electricity demand due to increased use of air conditioning, leading to peak demand that can result in **rolling blackouts or even total blackouts**. This poses a serious threat to electrical grids. * **Productivity Loss:** High air temperatures impact human productivity, especially in cities and indoor occupational settings. * **Water Resources:** Heat waves, especially when combined with drought, can lead to **increased demand for water and electricity, resulting in shortages of resources** and potential food shortages if agricultural production is damaged. * **Emergency Services:** Emergency services (staff and vehicles), hospitals, and mortuaries can be overwhelmed during a crisis. Paramedics may even become prone to heat stress themselves due to overwork. * **Environmental Impacts:** Heat waves can affect the environment beyond human health, including **emissions of volatile organic compounds (VOC) from urban/suburban vegetation and corresponding ground-level ozone levels**. Plants themselves are vulnerable, with impacts ranging from sub-lethal to lethal effects, secondary ecosystem effects, and complex interactions with other disturbances like drought. ### III. Strategies for Mitigation and Adaptation Effective management of heat wave impacts requires a multi-faceted approach involving short-term responses and long-term planning. #### A. Heat Health Warning Systems (HHWS) These systems are crucial for immediate public health responses. An effective HHWS requires: * **Scientific Basis:** Development of city-specific air mass classification systems and statistical algorithms that describe the relationship between daily mortality/morbidity and meteorological data (temperature, humidity, wind speed) and heat stress indices. * **Clear Criteria:** Defined criteria for releasing and closing warnings, often based on temperature thresholds linked to excess mortality. * **Lead-Times:** Warnings transmitted to the public ideally **1 to 3 days in advance**. Some systems have multiple steps, with initial warnings given 2-3 days in advance, a second warning 1 day in advance, and a third 12 hours before the event. * **Targeted Communication:** Warnings should target the **whole population**, with special emphasis on vulnerable groups (families with small children, elderly, ill people, tourists, outdoor workers) and institutions responsible for their welfare (health service providers, care workers, sport event organizers). * **Multi-media Approach:** Utilize mass media (TV, radio, public websites), bulletins, web pages, and leaflets for dissemination. * **Localized Advice:** Advice should be **contextual to place and include cultural considerations**, providing more detailed guidance for populations not accustomed to heat. * **Integrated Warnings:** Link heat advice with warnings about other related hazards like **ultraviolet radiation and air pollutants (e.g., ozone)**, to avoid separate alerts. * **Intervention Plans (Examples from Philadelphia, Rome, and Lisbon):** * **Community Outreach:** Encourage friends, relatives, and neighbors to visit elderly people daily. * **Hotlines:** Operate telephone hotlines for information and counseling. * **Cooling Centers:** Utilize public air-conditioned buildings (e.g., senior centers, shopping centers, public swimming pools) as cooling centers, potentially with free transport. * **Home Visits:** Department of Public Health mobile field teams make home visits to high-risk individuals. * **Institutional Alerts:** Inform nursing homes, hospitals, and other facilities about high-risk situations and offer advice. * **Utility Coordination:** Utility companies and water departments halt service suspensions during warning periods. Warnings should also be communicated to electricity providers to avoid power failures. * **Emergency Services Staffing:** Increase staffing for fire departments and emergency medical services. * **Support for Homeless:** Provide daytime outreach for homeless people. * **Evaluation and Improvement:** HHWS effectiveness in reducing mortality needs formal evaluation. This includes assessing if all social groups have equal access and ability to use information, and considering factors like language barriers and access to broadcast media. #### B. Urban Planning and Building Design Long-term strategies focus on reducing the UHI effect and improving urban resilience: * **Climate-Related Urban Planning:** This includes maintaining and improving ventilation paths, restoring connection to ventilation paths, reducing pollution in sensitive areas, and reducing overall heat load. Since 1976, Germany's Federal Development Law has stipulated that climate, air pollution, and health be important factors in urban planning. * **Green Infrastructure:** Increasing green spaces (e.g., tree planting projects, urban parks, green roofs) can reduce urban temperatures and provide additional benefits like increasing a city's attractiveness for business and tourism. * **Building Regulations and Design:** Develop regulations that reduce thermal stress, air pollution, and increase quality of life. Incorporate these into new constructions and renovations. * **Favorable Indoor Climates:** Design buildings to create favorable indoor climates without excessive reliance on air-conditioning. Campaigns can educate the public on optimal indoor temperatures (e.g., cooling offices to no less than 25°C or 28°C) and proper use of windows and shading devices to minimize energy consumption and avoid power failures. * **Addressing Nighttime Temperatures:** Emphasize that high nighttime temperatures detrimentally affect health, and educate the public on strategies to mitigate this. * **Reduce Motor Vehicles:** Every motor vehicle is a source of anthropogenic heat, worsening the UHI effect. * **Education and Training for Professionals:** Train planners and architects in climate-relevant planning and building. Educate policymakers and local administrators to establish and enforce regulations. #### C. General Preparedness and Education * **Public Education Campaigns:** Develop long-term educational and health promotion strategies to raise awareness of heat hazards. Distribute guidelines for specific target groups like schools, residential care homes, and tourist resorts. * **Social Resilience:** Education and training are key to building social resilience to heat stress, empowering individuals to take risk-reducing actions. * **Identify Vulnerable Individuals:** Compile lists of elderly people who live alone or others who might need assistance, so workers can call or visit them. * **Coordination:** Preparedness plans should involve multiple partners, including city managers, public health and social services workers, emergency medical officers, and private organizations. A structure with funding and regular meetings is essential to ensure knowledge retention and uninterrupted information flow. ### IV. Key Challenges and Research Gaps Despite progress, several challenges and knowledge gaps remain: * **Definition Consensus:** A lack of consensus on heat wave definitions and thresholds among the scientific community poses a limitation for comparative analysis and can impact public health policies. * **Effectiveness Evaluation:** More research is needed on the effectiveness of specific interventions and early warning systems in reducing heat-related mortality and morbidity. * **Data Availability:** Mortality information may not always be available, or studies may be too costly for many communities. * **Interaction with Other Hazards:** Very little work has been carried out on the interaction of extreme heat with other hazards and pressures on the city, such as air quality or water security. * **Cultural Context:** Advice given during a heat wave must be adapted to the social and behavioral context of the target population, as climate and culture differ significantly across regions. * **Informing Decision-Makers:** The urgency for generating more reliable information and investing additional resources in this sensitive knowledge area is clear, to help decision-makers understand the impacts and prioritize actions. In essence, navigating the increasing frequency and intensity of heat waves is like steering a ship through a rapidly warming ocean. City managers, elected officials, and property managers are the captains, responsible for charting a course that not only avoids immediate icebergs (sudden health crises, power outages) through robust warning systems and immediate interventions, but also involves redesigning the vessel itself (urban planning, building codes) and training the crew (public education, professional development) to withstand the long-term, systemic changes of the climate. The success of this journey depends on continuous monitoring, collaborative action, and the courage to adapt to a new normal.