ISSUE BRIEF

Research. Innovation. Sustainability

HEATWAVE
A string of deadly heatwaves has impacted millions around the world in 2019.
This issue brief examines the cause and the implications of heatwave forour path towards sustainability.

In the news
A string of deadly heatwaves has impacted millions around the world in 2019. Beginning early in the year with extreme heat
episodes in Australia and the Middle East, by early May temperatures then soared to 51°C in northern India and Pakistan, andin June temperatures exceeded 45°C in some parts of Western Europe. By the end of June, the heatwave in India became oneof the longest ever recorded and killed hundreds of people. Its impacts were compounded by water shortages, leading to riots,violence and major migrations out from rural areas. In Spain, the 2019 heatwave has sparked the worst wildfires in 20 years forcing
evacuations and drawing on military emergency personnel. These events occurred unseasonably early and are longer and hotter
than previous heatwaves.

Why is this happening?
As climate change intensifies, disruptions to traditional global atmospheric circulation systems, such as the jet stream in thenorthern hemisphere, are expected across the planet, leading to more frequent and intense extreme climate events. In particular,
smaller differences in temperature between the poles and the equator can slow the jet stream, leading to a buildup of high or low
pressure weather systems, resulting in more persistent hot-dry extremes in mid-latitudes.1 The current heat wave in Europe is linked
to a slow-moving system in the North Atlantic that allowed hot air from the Sahara to move north.2 In Pakistan and northern India,
the heatwave lasted longer than usual due to a delayed start to the seasonal monsoon. This may become more common in thefuture as a shifting seasonality of the monsoon is expected with climate change.3

Why does this matter?
We live in a warming world. As average global temperatures rise, so too does the probability of more extreme hot temperature
anomalies, resulting in earlier, longer and more frequent heatwaves.4 5 Heatwaves now pose a recurring challenge on all inhabited
continents and generate an increasing range of threats to human lives and well-being,6 particularly in cities where built environments
magnify heat exposure.7 This matters because close to 70% of the world’s population is expected to live in cities by 2050 and will
be exposed to extreme heat.8

What are the implications for our path towards sustainability?
Heatwaves have multiple cascading social, ecological and economic implications in the immediate and long term. Below we
explore some of the ways that heatwaves can negatively impact our world. We then describe effective measures to respond to andmitigate the impacts of extreme heat, helping us move towards a more sustainable social and environmental future.

•SOCIAL IMPACTS: Extreme heat can lead to heat-related illness and death, particularly in elderly populations, the poor, outdoorworkers, and in urban areas. For example, during the 2003 European heatwaves an estimated 70,000 additional people died
due to the heatwaves,9 and in the United Kingdom alone, the impact of this heat wave was estimated at £41M in health-related
costs and productivity.10 Heatwaves exacerbate the urban heat island effects, amplifying temperatures in built environments,and resulting in poorer air quality due to the creation of ozone that negatively impacts health.11 Heat-related mortality isexpected to be higher in cities, particularly those characterized by high population density, inequalities, limited access tohealth care, high pollution levels and fewer green spaces.12
Moreover, heat-related social impacts are not evenly distributed across populations. Wealthier people have greater opportunities,
compared to poor populations, to access water, cool environments, air conditioning and/or relocate, thereby exacerbatingsocial and economic inequalities. Poor neighbourhoods and informal settlements, such as slums that today house more than
800 million people globally,13 are more often exposed to environmental risks like heat, due to poor infrastructure, building
design and disadvantaged locations.14 15 Droughts increasingly accompany heatwaves 16 17 18 and can lead to violence overscarce resources.19

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ECONOMIC IMPACTS: Multiple areas of the economic sector experience

reduced worker productivity during heatwaves, especially agricultureand construction. Globally, 2% of total working hours is projected to belost every year, either because it is too hot to work or because workers
have to work at a slower pace. Lost productivity from heat stress at work,
particularly in developing countries, is expected to be valued at $4.2
trillion dollars per year by 2030, driving more inequality.20 The agriculturalsector, where 940 million people earn their livelihood, is set to be harder
hit by hotter temperatures, pushing workers, crops and livestock pasttheir physiological heat and drought tolerances.21 22 This will result in lostlabour, in smaller harvests for farmers, higher prices for consumers, andnegative impacts on livelihoods. For example, during the 2012 heatwave
in the United States, maize yields dropped by 13%, resulting in a sharp
increase in global corn prices because the United States supplies 40% ofglobal production. In the short term, such weather events resulting in foodprice volatility put low-income countries, and those with high crop importdependency ratios, at risk of food insecurity.23
In parts of India, changes to weather patterns and the resulting impacts onagriculture and other sectors are expected to translate into a 9% decreasein standards of living by 2050 assuming no adaption.24 A World Bank reportsuggests that by 2050, about 600 million Indians will live in places that
could experience loss of living standards, which could cost 2.8% of theGDP, stalling efforts to pull large parts of the population out of poverty.25
Increasing energy demand for cooling also comes as an extensive
economic cost to residents, businesses, and governments. Often energy
grids are unable to supply the required power for air conditioning in cities
during heatwaves.26 27 This results in not only increased emissions fromcarbon-based energy sources, but the failure of power grids, loss of power
to businesses, hospitals, and critical infrastructure – compounding loss ofproductivity, increased costs for the energy sector, and reduced access tolife-saving cooling and medical care. New power infrastructure is needed
to support this demand in some areas and new lower-emission lowerheating technologies are critical. With these extreme heat events, the needfor access to cooling should be viewed as a basic necessity – not just for
health and productivity reasons but, in some cases, even for survival.28•ECOLOGICAL IMPACTS: Heatwaves, without concomitant increases inprecipitation, can lead to water shortages and increased stress for plants,
particularly in arid regions.29 This has the effect of reducing plant growth,
the basis of energy production and the food chain, with an overall dryingout of the landscape. In Europe, the 2003 heatwaves caused tree damage,increased leaf fall and turned carbon-sink landscapes into carbonsources, releasing more CO2 into the atmosphere than was absorbed.30These hot and dry conditions are favourable to the start and rapid spreadof forest fires, which now regularly accompany heatwaves. In 2010, during
the heatwave in Russia – which was the hottest in 130 years – more than
15 million hectares of forest, vegetation and peat land areas burnt, andimportantly in areas without fire-tolerant species.31 Heatwaves can also dryup shallow aquatic ecosystems and accelerate glacier melt. For example,
the 2003 European heatwave resulted in a 10% loss in glacier mass inEurope, which was five-times more than the average annual loss.27 Similar
impacts were reported for the French Alps in 2019. Over time, such deep
permafrost warming and thawing could cause landslides and rock falls,continuing the negative ecological impacts.27

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Heatwaves and health:a new opportunity forinnovation & research

As the effects of heatwaves become
more frequent and visible, funding andresearch targeting heat and health isa high global priority. For example, theSeptember 2019 UN Climate Action
Summit coalition on social and politicaldrivers is advocating for key actions thatcities and governments can invest in likeheat protection. It is also encouraging
developmentbanks,philanthropy,and private sector to commit funds forclimate-informed health surveillance
and response systems for heatwaves.
Similarly, the Belmont Forum hasprioritized heat and health as one ofthree themes for the 2019 funding call on
Climate, Environment, and Health where€11M in cash and in-kind resources iscommitted to support up to 12 research
projects. The European Commission’s
Horizon 2020 has committed around 35%of the €80B research fund for climaterelated expenditure, including healthresearch to better understand current
and future heat risks for the EU.
On the research and application front,
the World Climate Research Programmestudies global climate systems evolution
to inform societal understanding of risks.
The World Weather Research Programmeadvances society’s ability to cope withhigh impact weather by focusing on
improving the accuracy, lead time andutilization of weather prediction. The
Global Heat Health Information Network
is a group of scientists, professionals
and policy-makers working to enhanceresearch to action and promote sciencebased decision tools to better manage
heat risks. Regular events and an online
learning center provide resources onheat health including case studies ofheat management tools and models
already in practice. The Climate Services
for Resilience Development is a large
public-private initiative that focuses onheat (and other) risks, by developing new
guidance and online decision tools.
And at Future Earth, heat is a crosscutting theme across the work of our
Health, Urban, and Risk KnowledgeAction Networks, that seek to generate
multi-faceted knowledge to inform
solutions for complex societal issues.

2Pathways forward to sustainability
The most effective way to avoid the negative impacts of heatwaves is to mitigate climate change by reducing greenhouse gas
emissions (GHG) and minimize the rise in global mean temperatures. In particular, shifts towards cleaner energies will not only
reduce GHG emissions, but will also reduce localized air pollution and heat island effects within cities.11 12 Secondly, new initiatives
to create early warning and response systems32 and improved communication approaches33 can help to save lives and build
resilience to heatwaves. Thirdly during a heatwave, decision-makers can employ a range of strategies and policies to modify social
behaviour and reduce exposure to heat by closing schools or offices which lack adequate air conditioning, ensuring availabilityof water, health care and first aid, and extending access to pools, parks and public cooling centers.34 Finally, improved urban
design and sustainable planning that increases the amount of and access to green space and other cool environments (pools,air-conditioned spaces) and encourages white roofs, will play an important role in avoiding heat-related illness, in reducing surface
temperatures, and in providing a wealth of other nature-related benefits.35 36 37

Produced in collaboration with:

Dr. Joy Shumake-Guillemot,
World Health Organization/World Meteorological Organization Climate and Health Office co-chair of Global Heat Health
Information Network
Dr. Kristie Ebi,
Professor Department of Global Health, School of Public Health, University of Washington, co-chair Future Earth Health
Knowledge-Action-Network
For more information, please contact us at:
contact@futureearth.org

July 2019

References
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