This summer has been warm, with several heatwaves affecting Europe. In some places in Finland it was recorded 22 consecutive days above 30 degrees in July, also Norway and Sweden faced heatwaves this summer (earth.org).
In Spain and Portugal, temperatures soared to 46 degrees, while France closed schools and the Eiffel Tower due to a forecast of 41 degrees in early July. A new heatwave was affecting Southern Europe in August.
As the climate warms, the associated hot temperatures have physical consequences for both nature and society, including health challenges.
In her newly completed doctoral thesis at the University of Oslo, Iulia Marginean has focused on climate risk related to extreme heat in cities and its impacts on public health. She placed vulnerability at the center of risk assessments.
"Extreme heat is one of the challenges of climate change, especially for those living in urban areas. Dark, impervious surfaces in cities contribute to the so called 'urban heat island effect,' where asphalt and concrete absorb heat from the sun, thus making cities substantially warmer than their surrounding areas," Marginean points out.
Health-related consequences of extreme heatwaves
Persistent heatwaves can have significant consequences, especially for vulnerable groups. A scientific study estimated that over 60,000 deaths in Europe between May 30 and September 4, 2022, were related to heat. Of these, around 4,800 deaths were registered in the age group 0-64, further 9,200 deaths in the age group 65-79 and over 36,000 deaths among people 80 years old and above.
Furthermore, the study registered 63% more deaths of women compared to men.
In her study Marginean investigated how climate change affects health-related climate risk in urban areas, by combining climate impacts research with insights from epidemiology, and the social sciences.
What health challenges are associated with extreme heat?
"We distinguish between direct health impact, which can result in heatstroke, worsening of existing diseases and mental health depreciation. These outcomes are measured by accounting for hospital admissions, and in the most extreme cases, premature deaths. Additionally, we have indirect health impacts, where heatwaves can increase transmission of some communicable diseases, affect healthcare services and facilities, impact ecosystems by enhancing drought and fire events, and poor air quality, explains Marginean.
– How are people affected by heatwaves?
"Symptoms can range from mild discomfort, which can usually be alleviated by taking individual precautions, to more severe reactions such as fainting, exhaustion, and heatstroke that require emergency care. In cases of heatstroke, the individual should be hospitalized. The ultimate consequence of heat danger is premature death," she points out.
Heat does not affect everyone equally, having a higher impact on people in vulnerable groups. Vulnerability is defined as the tendency to be more affected by extreme conditions due to individual characteristics such as age, sex, sosioeconomic status, etc.
High-risk groups
Vulnerability is commonly defined as a function of exposure, sensitivity and adaptive capacity. For health-related risks and vulnerability to heat, it also matters that some people have a lower tolerance for heat than others.
"People with chronic disabilities, pregnant women, small children, and older adults are most at risk. There are also individuals in challenging life situations, such as homeless people living outside, or workers engaged in physically demanding jobs", explains Marginean.
Health-related risks can be reduced
To reduce climate risk and counteract the negative consequences of climate change, a variety of measures are available.
It is possible to reduce greenhouse gas emissions, and multiple adaptation solutions can be implemented at national, municipal, and individual levels.
"One overarching climate measure is the reduction of greenhouse gas emissions, which we can achieve for instance by transitioning to renewable energy sources as an alternative to fossil fuels. Wind, hydro, and solar energy are perhaps the most common renewable energy sources. Governments can also impose requirements for carbon emissions reductions in different sectors. While a necessary step, emission reduction is not enough to counteract the already visible negative impacts from climate change," says Marginean, and adds;
– "We also need to adapt to the warming climate. Measures that have a localised impact include increasing forest areas and creating more green space in cities. Increasing green areas also helps reduce urban air pollution," she points out.
It is local governments that are responsible for developing strategies to protect citizens from the impacts of heatwaves.
The local strategies typically include issuing heatwave alerts, ensuring the availability of drinking water, and managing heat stress in buildings. Local measures also focus on emergency services, such as fire departments and hospitals, and ensuring public transportation and utility access during heatwaves.
Healthcare measures may involve temporarily increasing staff in hospital emergency rooms, training on heatwave management, providing necessary medical equipment, and assistance targeted at vulnerable groups.
When the heatwave strikes!
The most common advice during heatwaves for citizens in major cities include avoiding outdoor activities during the hottest parts of the day, staying in the shade, and staying informed.
"When heatwaves are forecasted in urban areas, individuals can cope by reducing their activity levels and dressing appropriately for the conditions. It is also important to drink plenty of water to maintain hydration. People often change their daily routines and cool their homes by increasing ventilation and shading," says Marginean.
Action plan for heat-related health challenges
The ultimate consequence of heatwaves in urban areas is heat-related deaths, especially among vulnerable populations. To avoid such fatalities, it is crucial to be proactive and develop heat and health action plans (Heat-Health Action Plans).
"It is important to include vulnerable groups in the development of the heat-health action plans and implementation of measures to strengthen how those groups who have the highest health risk cope with overheating," concludes Marginean.
About the doctoral study:
Read about the doctoral study here: Heat impacts on human health in cities and the role of vulnerability in climate risk. Interdisciplinary research on urban overheating.
Iulia Marginean's doctoral thesis was defended on June 25, 2025 at Department of Geosciences/Faculty of Mathematics and Natural Sciences, University of Oslo.