Heat waves and climate change

Climate change is deemed “the biggest global health threat of the 21st century”. (1) Global warming is now unequivocal; global average temperatures have risen by 0.85°C between 1880 and 2012. (2) Global mean temperature is projected to increase by about 1.6 to 2.6°C above the preindustrial period by the 2050s, depending on the scenario used.2 Using median values, projected temperature increases for Europe and America are between 2 and 4°C for the 2050s (relative to present-day climate). (2) Higher increases are projected over much of Asia and Australia. (3) Heat waves, defined as extended periods of extreme high temperature, are regarded as one of the primary weather-associated threats to human life. (4) As increased frequency, intensity, and duration of heat wave events occurred associated with global warming, impact of heat wave on health has drawn more and more attention worldwide. (5-7) It is well-established the relationship between extreme high temperatures and human morbidity and mortality. (8)

There is also now strong evidence that such heat-related mortality is rising as a result of climate change impacts across a range of localities. (9) For instance, the excess mortality during the extremely hot summer of 2003 in Europe and the 2010 Russia heat wave, resulted in more than 70,000 and 11,000 deaths, respectively. (10,11) Much of the excess mortality from heat waves is related to cardiovascular, cerebrovascular, and respiratory disease and is concentrated in some populations groups. These groups include women, young children and older people, people with existing health problems or disabilities, and poor and marginalised communities. They are particularly vulnerable to the health effects of climate change, whether because of existing socioeconomic inequalities, cultural norms or intrinsic physiological factors.

Other risks were associated with rising temperatures and changes in precipitation pattern. For example, the modification of viable distribution of disease vectors such as mosquitoes carrying dengue or malaria. Temperature affect the range and reproductive rates of malarial mosquitoes and also affect the lifecycle of the parasitic protozoa responsible for malaria, possibly increasing the incidence of a disease that causes 660 000 deaths per year. (12) There are equally complex relationships and important climate-related risks associated with dengue fever, cholera and food safety. (13-15)

Moreover, a heat wave can be a big threat in urban area because of the “urban heat island (UHI) effect”. The UHI effect results in the temperatures being somewhat higher in cities than in suburban and rural areas, primarily because of the abundance of heat-retaining surfaces such as concrete and black asphalt, that exacerbate the negative heat effect on residents compared with reflective, transpiring, shading, and air-flow-promoting vegetation-covered surfaces. (16,17)

The events occurred in Europe and Russia and those which occurred in Australia, 2012/2013 and 2016/2017; North America, 2012; India and Pakistan, 2015 and Europe 2015 have led to the implementation of specific policies to reduce heat-related mortality such as the National Heat Wave Plan in France, (18) and the Heatwave Plan for England. (19) Evidence suggests that effective adaptation measures would reduce the death rates associated with these heat waves. Adaptation measures also include increasing green infrastructures and urban green spaces, improving the design of social care facilities, schools, other public spaces, and public transport to be more climate-responsive. Adaptation options within health care include training of health-care workers and integrated heatwave early warning systems (HEWS). (20)

A communication and public education strategy is an essential part of the warning system, public health messages should be disseminated to all age and vulnerable groups to increase awareness of symptoms of heat-related illness.



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  2. IPCC, 2013a: Summary for Policymakers In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change Change [Stocker TF, Qin D, Plattner GK, Tignor M, Allen SK, Boschung J, Nauels A, Xia Y, Bex V, Midgley PM (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 1–30.
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  6. Gronlund C, Zanobetti A, Schwartz J, Wellenius G, O’Neill MS. Heat, heat waves, and hospital admissions among the elderly in the United States, 1992–2006. Environ Health Perspect. 2014; 122: 1187–1192.
  7. Gao J, Sun Y, Liu Q, Zhou M, Lu Y, Li L. Impact of extreme high temperature on mortality and regional level definition of heat wave: a multi-city study in China. Sci Total Environ. 2015; 505: 535–544.
  8. Forsberg, B. Heat-related respiratory hospital admissions in Europe in a changing climate: a health impact assessment. BMJ Open. 2013; 3: e001842.
  9. Smith K, Woodward A, Campell-Lendrum D. Human health—impacts adaptation and co-benefits. Climate change 2014: impacts, adaptation, and vulnerability Working Group II contribution to the IPCC 5th Assessment Report. Cambridge University Press, Cambridge, UK and New York, NY, USA; 2014.
  10. Robine J, Cheung S, Roy S, Oyen H, Herrmann F. Report on excess mortality in Europe during summer 2003. EU Community Action Programme for Public Health. Grant Agreement 2005114. 2007.
  11. Agence France-Press. Russian heat wave caused 11,000 deaths in Moscow: Official. 2010. Press release. 2010.
  12. WHO. World malaria report. World Health Organization, Geneva; 2012.
  13. Bhatt S, Gething P, Brady O. The global distribution and burden of dengue. Nature. 2013; 496: 504-507.
  14. Sutherst R. Global change and human vulnerability to vector-borne diseases. Clin Microbiol Rev. 2004; 17: 136-173.
  15. WHO. World Meteorological Organisation. Atlas of health and climate. World Health Organization, Geneva; 2012.
  16. Roth M. Review of urban climate research in (sub) tropical regions. Int J Climatol. 2007;27:1859–1873.
  17. Gabriel K, Endlicher W. Urban and rural mortality rates during heat waves in berlin and Brandenburg. Germany Environ Pollut. 2011;159(8–9):2044–2050.
  18. Pascal M, Le Tertre A, Saoudi A. Quantification of the heat wave effect on mortality in nine French cities during summer 2006. PLoS Curr. 2012: 4:RRN1307.
  19. Public Health England. 2015. Heatwave Plan for England. Protecting health and reducing harm from severe heat and heatwaves. Public Health England, London, UK.
  20. Ghasem S, FitzGerald G, Aitken P, Verrall K, Tong S. Are heat warning systems effective? Environmental Health. 2013: 12-27.


Ana Pinto de Oliveira
Public Health Resident
Arnaldo Sampaio Public Health Unit, Lavradio, Portugal

Catarina Oliveira
Public Health Specialist
Arnaldo Sampaio Public Health Unit, Lavradio, Portugal