CM – Provision of heat officers, guidelines and metrics

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Ladd Keith is Assistant Professor of Planning at the School of Landscape Architecture and Planning, University of Arizona, Tucson, Arizona, USA.

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Sara Meerow is an Assistant Professor at the School of Geographical Sciences and Urban Planning, Arizona State University, Tempe, Arizona, USA.

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David M. Hondula is an Associate Professor in the School of Geographical Sciences and Urban Planning, Arizona State University, Tempe, Arizona, USA.

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V. Kelly Turner is Assistant Professor of Urban Planning and Co-Director of the Luskin Center for Innovation, Luskin School of Public Affairs, University of California, Los Angeles, Los Angeles, California, USA.

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In June, residents in Portland, Oregon fill a refrigeration center to escape record-breaking temperatures.Credit: Nathan Howard / Getty

In June, temperatures soared in the glowing « heat dome » that spilled over the western states for weeks North America was 20 ° C above average in some places. Lytton, a village in British Columbia, hit Canada’s previous national high of 49.6 ° C before wildfire devastated the city (see Nature 595, 331-332; 2021). Across the region, more than 1,000 people died from the heat wave.

At its peak, more than 1,000 people in Oregon and Washington visited the emergency room every day due to heat exhaustion and heat stroke, compared with 9 people in 2019. Some found relief in air-conditioned rooms Libraries and Convention Centers. Many – especially the elderly – were unable to reach these cooling centers. Of the 54 additional deaths in Multnomah County, Oregon (maximum temperature 46.7 ° C), 80% were over 60 years old. Most of them lived alone.

The governments were insufficiently prepared. The heat wave was predicted, but no one “owned” the problem. Heat is an outlier danger – invisible, often chronic, and subtly ubiquitous. Unlike in the case of floods or wildfires, no single organization or department is responsible for coordinating action in extreme heat. Many residents lack the resources.

To be fair, heat is a complex hazard. It’s more than air temperature – surface and radiation temperatures, air movement and humidity all affect the warmth we feel. Urban areas tend to be hotter than their surroundings (the urban heat island effect). But even in cities, the perception of warmth can be very different from block to block or from a bench under a shady tree to one in full sun. The effects of heat depend on local contexts and inequalities1. Everyone is in danger. Most affected are people who are marginalized, poor, young, old, homeless, in care or have pre-existing conditions2.

The effects of extreme heat will intensify. Heat waves are becoming more frequent, more intense, longer and lasting as the climate warms up. July 2021 was the hottest month ever recorded worldwide. Europe also posted record highs in August, when Sicily reportedly hit 48.8 ° C.

A handful of places have taken action. That year, Miami-Dade Counties, Florida and Athens, Greece named the world’s first two chief heat officers; Phoenix, Arizona established the first publicly funded Office of Heat Response and Mitigation. Much remains to be done.

We call for a focused research program to support “heat governance” – including the actors, strategies, processes and institutions that can reduce and cope with this risk. Institutions and policies need to be developed to combat heat at all levels of government. And that requires a strong evidence base.

Required heat property. Racism and income inequality affect people’s ability to access health care, education, housing, energy and jobs, and to participate in government decisions. All of this dictates the results of the exposure to heat. The lack of air conditioning in homes is an important predictor of heat illness and death. But in 2017, 840 million people had no electricity. In some US cities, including Chicago and Detroit, white residents are more than twice as likely to have air conditioning as black residents3. In Pakistan, only 5% of low-income people are expected to have indoor cooling by 2050, compared to 38% of highest-income people4.

Damp heat is particularly punishable by law. Several cities in Pakistan have already experienced temperatures and humidity levels higher than the human body can survive – a threshold that climate models suggest would extend beyond 20505. Extreme humid heat has more than doubled since 1979.

Most heat susceptibility analyzes focus on identifying neighborhoods most susceptible to hot temperatures, but the heat risk is more nuanced. Researchers need to consider equity when examining how multiple risk factors converge, as well as when assessing the tradeoffs between different strategies for combating heat. Air conditioning, for example, causes greenhouse gas emissions; Urban greening increases water consumption. Such disadvantages could be more acceptable in resource-poor districts, at least in the short term, than in more affluent areas, where residents can more easily adapt. In the longer term, low-carbon indoor cooling and urban shading with low water consumption should be a priority.

Decision-makers need to engage with communities to understand who is most influencing the heat, why and how best to manage it. A good example is the US National Integrated Heat Health Information System (NIHHIS), which was jointly developed by the Centers for Disease Control and Prevention (CDC) and the National Oceanic and Atmospheric Administration (NOAA). An NIHHIS project trained promotoras (community health workers) and maternal health care providers in the US-Mexico Juárez-El Paso binational region to improve heat health. Expectant mothers were given bilingual health materials to help identify dehydration and symptoms of heat stress.

Mitigate heat. Urban planners and designers have many strategies for keeping cities cool. You can shape land use through planning and development regulations6. You can protect natural areas, plant trees, make hard surfaces more reflective, create spaces to encourage airflow, and minimize waste heat from air conditioning and vehicle exhaust. Researchers need to find out how effective these strategies are in different places and conditions, how they interact, and what cumulative effects they have. For example, ventilation corridors are more effective in densely populated cities with tall buildings such as Hong Kong and Tokyo. Models suggest that reflective “cool” roofs would lower temperatures by 0.2 ° C more in humid cities like Florida, but by 1.2 ° C more than green “green” roofs in drier cities like California7.

Compromises have to be weighed up. In Los Angeles, for example, a trial with a coating that makes roadways cooler by making them lighter achieved its stated goal8: It reduced land surface temperature (LST) by 4–6 ° C. Due to the reflected heat, however, the mean radiation temperature (MRT) above the paving rose by 4 ° C around noon compared to untreated asphalt. In another example, a model of urban greening in Phoenix showed that a 20% increase in vegetation would cool the city, but at the cost of an almost 33% increase in water use9.

Thermal protection must also target areas used by higher risk groups. This means that urban greening focuses on areas with the least amount of vegetation, often the poorest, rather than on greener suburbs. In public places with the most passers-by, such as transport hubs and shopping areas connected by cool corridors for pedestrians and cyclists, the shade should be increased.

Manage risks. Governments can also rely on a number of thermal management strategies. These include: early warning systems, health campaigns, guidelines to protect outdoor workers, and programs to make indoor cooling and energy more affordable and accessible. Researchers need to determine the effectiveness of each strategy and how the effectiveness differs between populations.

For example, few studies have evaluated extreme heat early warning systems, although some have been in operation for decades. In Baltimore, Maryland, the health commissioner has issued a Code Red Extreme Heat Alert since 2006 if the air temperature exceeds 40.6 ° C. Text messages are being sent, media are relaying information and cooling centers are being opened. Ahmedabad, India, passed a heat action plan in 2013 after a 2010 heat wave killed more than 1,300 people. The plan, updated in 2019, includes public awareness workshops, multilingual media releases, an early warning system and training for health professionals. Such systems should be continuously evaluated; Ahmedabads are reviewed every year.

Management also needs to expand to treat chronic heat. For example, from 2015 to 2019 in Maricopa County, Arizona, only 23% of heat-related deaths occurred on days with a heat warning. In tropical and subtropical climates, high temperatures and humidity can persist for months10. The school learning rate decreases with the number of hot days11.

Develop metrics. Measures that evaluate progress towards heat reduction and management goals must be agreed and consistently recorded. For example, public health officials could focus on preventing heat-related illnesses and deaths, while city planners could measure success by lowering temperatures in the neighborhood. Governments need a number of metrics that span scales and sectors.

Merging different types of heat is a problem. Urban heat islands are typically measured using LST derived from satellite imagery. The thermal exposure of humans is often measured in the form of MRI, which combines several factors such as humidity, wind and radiant heat. As the cool Pavement study in Los Angeles showed, interventions that reduce LST can worsen MRI.

Researchers need to advise decision makers on what temperature levels are appropriate for goals and mitigation strategies. Social impact, time of day and time of year must be taken into account. For example, the urban heat island effect is often strongest at night and early in the morning, but increasing shade during the day could be more effective from a public health perspective.

Sprinklers set water vapor along a street in Dubai, United Arab Emirates during an August heat wave , Free.Credit: Karim Sahib / AFP / Getty

Although the number of visits to refrigeration centers is sometimes logged, the effectiveness of these facilities in preventing disease and death is rarely measured. Cold centers are often only open during the day, not at night, and heat can prevent the body from sleeping and rest. They are usually closed outside of the “official” heat wave periods, even if the high temperatures persist.

Reports of climate change often focus on global average temperatures, but even a small change in average temperatures becomes a large increase in extreme days Heat. For example, climate models suggest that an increase from 1.5 ° C to 2 ° C would almost triple the percentage of the world’s population exposed to severe heat waves at least every 5 years from 14% to 37 ° C.

Heat ratios will be often reported inconsistently. Mortality estimates differ by local and national census and are lower than those statistically derived from excess mortality. Heat often kills indirectly, and some deaths, such as a heat-induced heart attack, may not appear on coroner’s reports. Although 37% of heat-related deaths worldwide are attributed to man-made global warming, there is a lack of empirical data in the Global South, an area where the rise in temperature is very worrying10.

Coordinate initiatives. Dedicated urban roles, processes and organizational structures are required for heat management. These must include: urban planning, public health, emergency management, housing, infrastructure, finance, health care and energy. Research into which systems are most effective at regulating heat would help cities learn from each other.

Local community plans and guidelines should be incorporated to avoid conflicting goals. For example, a plan might include more retail or residential construction to generate sales tax revenue, but the associated parking, road paving, and removal of vegetation will increase local temperatures. A positive example is the Cool Neighborhoods New York City report, which includes common goals on heat mitigation and management strategies, such as tree planting, reflective roofs, and developing buddy systems for at-risk residents.

Heat also spans limits jurisdiction and requires coordination at regional level. An example of good practice is the Western Sydney Regional Organization of Councils in Australia. The Turn Down the Heat plan of 2018 includes mitigation and management strategies with contributions from 13 municipalities, the private sector, universities and non-governmental organizations.

Build heating facilities. National governments should grapple with the large, unfair, and growing consequences of heat risks. This can have immediate benefits. For example, France’s National Heatwave Plan, implemented in 2006 after the 2003 heat wave that killed 15,000 people, saved more than 4,000 lives. It includes an alert system, check-ins for at-risk residents, air conditioning for old people’s homes, and more.

National programs should be put in place to coordinate the fragmented efforts. In the United States, NOAA administers heat warnings, the Environmental Protection Agency provides guidance on heat containment, and the CDC provides public health information and tracks heat-related diseases. In order to bundle these efforts, the NIHHIS was set up as an inter-agency working group and community of practice with local decision-makers. Yet it still lacks official authority and capacity. National governments should support similar initiatives.

Regulatory and political loopholes need to be closed. As with air and water pollution regulations, limits should also be placed on the heat generated by the built environment. « Cool community standards » should be adopted that integrate heat reduction strategies into development and building regulations. Governments should adopt best practices from areas similar to flood governance, where developers need to consider flood risks for new buildings.

New roles, processes, strategies and institutions need to be evaluated. Knowledge about heat governance should be exchanged internationally, for example through the Global Heat Health Information Network, which is organized by the World Health Organization and the World Meteorological Organization (see https://ghhin.org). The forum offers practitioners and researchers a good opportunity to build thermal management capacities on a local to global level.

Article

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article

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PubMed
items

Google Scholar

article

Google Scholar

PubMed
items

Google Scholar

article

Google Scholar

Georgescu, M., Morefield, P.E., Bierwagen, B.G. & Weaver, C.P. Proc. Natl Acad. Science USA 111, 2909-2914 (2014).

PubMed
items

Google Scholar

Middel, A., Turner, V.K., Schneider, F.A., Zhang, Y. & Stiller, M. Environ. Res. Lette. 15, 064016 (2020).

Article

Google Scholar

article

Google Scholar

article

Google Scholar

article

Google Scholar

Dosio, A., Mentaschi, L., Fischer, E.M. & Wyser, K. Environ. Res. Lette. 13, 054006 (2018).

Article

Google Scholar

As of the writing of this comment, D.M.H. has been named director of the Office of Heat Response and Mitigation for the City of Phoenix. He keeps his degree and position at Arizona State University.

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