The world is getting warmer. That much is clear. Recent reports highlight that 2023 is likely to be the hottest year on record, with heatwaves and extreme heat affecting people globally. Extreme heat is a genuine threat to life and impacts the vulnerable – the very young and the elderly – most of all. A report by Save the Children shows that a child born in 2020 will experience 6.8 times more heatwaves across their lifetimes than a person born in 1960. Pregnant women, infants and very young children are among those most at risk. As with many health hazards, inequalities play a role. Children living in densely-built and underserved areas, like inner city slums and informal settlements, are among those most seriously affected.
Heatwaves and extreme heat
There is no universal definition of a heatwave. One widely accepted understanding is that it’s an extended period that is hotter than is usual in a particular area for that time of year. Of course, “hotter than usual” means one thing in Oslo and something quite different in Delhi. While tolerance levels may vary to some degree, it is exposure to extreme heat and humidity, rather than heatwaves per se, that poses a risk. Although “extreme heat” can also be a relative term, it is generally considered that a wet bulb globe temperature (WBGT)[i] over 32°C poses a serious risk for vulnerable groups.[ii] This is particularly true when heatwaves last three or four days or more.
Over the last two decades, as climate change has warmed the planet, periods of extreme heat have become hotter, more widespread, more frequent and longer-lasting. Days considered unusually hot in the past are now on the high side of normal. A global study found that between 2009 and 2019, more than five million people on average died each year because of extremes in temperature. Deaths from exposure to cold exceeded heat-related deaths over this period, but with global temperatures rising, that is changing fast.[iii]
Intergovernmental Panel on Climate Change projections see heatwave-related disasters increasing at a rate far exceeding that of all other climate-related disasters.[iv] By 2050, more than one billion people could face heat stress unlike any in recorded history. Or for many of these people, extreme heat will not be a short term event, but rather a chronic state of affairs.
Rising temperatures and urban heat islands
Cities and towns in Asia and Africa are among those most affected by heat exposure. Densely built-up areas, with the accompanying loss of natural surfaces like soil, greenery and water, are considerably hotter than the surrounding rural environments – a phenomenon known as the urban heat island (UHI). Large cities can be 10 to 15 °C warmer than their surroundings.
Differences within cities can be just as great. People living in green neighbourhoods with well-spaced, well-ventilated housing experience heatwaves very differently from those in crowded, cramped conditions with little or no ventilation or vegetation. Many urban residents in slums and informal settlements also lack access to the amenities that make it easier to cope with heat, including enough drinking water to prevent dehydration, and electricity to power cooling devices. In a survey of over 4,500 low-income residents from crowded urban areas in Pakistan, India, Indonesia, and Cameroon, only seven reported having an air conditioning unit. Only 34 per cent used electric fans. About 40 per cent had less than 12 hours of electricity per day. [v]
How do heatwaves affect children?
Heat stress occurs when heat exceeds the body’s capacity to regulate its internal temperature, and pregnant women, infants and young children are especially vulnerable. In pregnant women, extreme heat can cause dehydration, hypertension, seizures and increased risk of stillbirths. Their infants are at higher risk of reduced birthweight and congenital defects.[vi]
Newborns exposed to high temperatures are more likely to develop jaundice and neurological dysfunction, and dehydration can affect their nutritional status. Babies and young children, due to their physiology, sweat less and overheat and dehydrate quickly. In extremely hot weather they can experience heat exhaustion and muscle cramps, and heat strokes can damage their brains, hearts, kidneys and muscles.
Children over five adapt more easily to high temperatures and are at lower risk of serious health problems, but can also become dehydrated and exhausted. Many children are lethargic when they are too hot, and when extreme heat is more or less chronic, it may undermine their desire for play, so fundamental to their development on all fronts. Extreme heat also impairs concentration and focus and is associated with lower academic performance and missed school days.[vii] This is yet another way that climate change may contribute to eroding socioeconomic gains among the world’s most vulnerable populations.[viii]
Heat affects everyone, especially the elderly, people who work outdoors in sectors like construction, and girls, women and caregivers. Cultural norms and concerns about safety often mean that girls and women are expected to spend more time indoors in poorly ventilated and intensely hot houses. They may also have less access to shady areas or public places that might be cooled by a breeze, and less able to take advantage of sleeping outdoors. They are also often expected to fetch water, a vital activity on extremely hot days, but one that risks heat exhaustion.
The conditions women face have a knock-on effect on the children they care for. Irritability is a notable effect of heat stress, especially for those who are sleep-deprived. Caregivers may also be less inclined to prepare nutritious meals for children when it means adding the heat from stoves to already sweltering indoor temperatures.
Because heatwaves tend disproportionately to affect people living in poverty, there may be little political activity around responding to urban heatwaves. As conditions become more punishing, local governments and communities must find ways to manage extreme heat using top-down and bottom-up strategies. The right steps can help protect the most vulnerable.
How can cities manage heat better?
The technical note, Protecting Children from Heat Stress by UNICEF, has several actionable ideas for addressing heatwaves, including the following suggestions:
- Promote and enact national and local multisectoral heat response plans. Bring together national and local sectoral agencies, including health, education, social services and urban development, to develop and implement local heat action plans. Fund and create new roles for heat officers, use innovative techniques to identify hot spots and at-risk communities and implement early warning heat alert systems. Caregivers should be consulted on what they most need in order to cope better.
- Adapt built environments for the long term. Ensure schools, early childhood centres and healthcare facilities are built with cool building technologies. Require developers to include indoor and outdoor heat-reducing infrastructure like cool roofs and green and blue spaces in residential and commercial development. Seed green canopies, particularly near schools, elderly facilities and low-income neighbourhoods. Make resources available to community groups in unplanned settlements to use the same approaches. Shaded spaces can reduce ambient temperatures by 11–25°C.[ix] Plan and drive equitable tree planting campaigns to reduce heat stress for low-income communities.
- Plan and implement a risk communication campaign. Take a ‘whole-of-society’ approach to raising awareness about heat stress and its impacts and provide people with the information and resources they need to protect themselves using effective communication and social and behaviour change strategies.
- Equip schools, early childhood centres, public spaces and primary health care facilities to deal with heat. Especially in low-income neighbourhoods, ensure places frequented by children are equipped to respond to heat protocols, and have water sprinklers, drinking water stations, tents, oral rehydrating solutions and fans. Outdoor time should be shifted to hours when the heat is lower, and hydration breaks should be scheduled every 30 minutes in schools.
Other useful resources for dealing with extreme heat include Heatwaves: Addressing a sweltering risk in Asia-Pacific by the United Nations Office for Disaster Risk Reduction and the Heat wave guide for cities by the International Federation of Red Cross and Red Crescent Societies.
About the author
This blog was written by the Urban Hub team at Save the Children.
[i] ‘Wet-bulb temperature (WBT) combines dry air temperature (as you’d see on a thermometer) with humidity – in essence, it is a measure of heat-stress conditions on humans.’ Source: Timperley J (2022) Why you need to worry about the ‘wet-bulb temperature’. The Observer, 31 July. Available at: https://www.theguardian.com/science/2022/jul/31/why-you-need-to-worry-about-the-wet-bulb-temperature(accessed 18 July 2023).
[ii] Met Office (n.d.) One billion face heat-stress risk from 2°C rise. Available at: https://www.metoffice.gov.uk/about-us/press-office/news/weather-and-climate/2021/2c-rise-to-put-one-in-eight-of-global-population-at-heat-stress-risk (accessed 18 July 2023).
[iii] Zhao Q, Guo Y, Ye T, et al. (2021) Global, regional, and national burden of mortality associated with non-optimal ambient temperatures from 2000 to 2019: a three-stage modelling study. The Lancet Planetary Health 5(7). Elsevier: e415–e425. DOI: 10.1016/S2542-5196(21)00081-4.
[iv] Masson-Delmotte V, Zhai P, Pirani A, et al. (eds) (2021) Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press. DOI: 10.1017/9781009157896.
[vii] Protecting children from heat stress: A technical note | UNICEF (2023). Available at: https://www.unicef.org/documents/protecting-children-heat-stress-technical-note%C2%A0 (accessed 12 July 2023)
[viii] Climate change can undermine children’s education and the development in the tropics | PreventionWeb (2019). Available at: https://www.preventionweb.net/news/climate-change-can-undermine-childrens-education-and-development-tropics (accessed 18 July 2023).
[ix] US EPA O (2014) Using Trees and Vegetation to Reduce Heat Islands. Available at: https://www.epa.gov/heatislands/using-trees-and-vegetation-reduce-heat-islands (accessed 12 July 2023).
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