The climate risk from heatwaves is expected to increase significantly across much of the Athens metropolitan area between 2031 and 2060 compared with the 1981–2010 period, according to findings from the CLIMASPIN research project.
The study maps both heatwave risk and vulnerability across the wider Athens urban area and highlights the need to integrate climate change considerations into urban and spatial planning.
Heatwave risk expected to increase across Attica
Konstantinos Kartalis, professor of environmental and climate physics at the National and Kapodistrian University of Athens and a member of the European Union’s Scientific Advisory Board on Climate Change, said heatwave risk is already high in central Athens and in the city of Elefsina, while it is classified as moderate in many other parts of the wider metropolitan area.
Between 2031 and 2060, the risk is expected to increase across all areas of Attica compared with 1981–2010.
In the wider Athens metropolitan area, as well as urban areas extending toward Elefsina and Megara, heatwave risk is expected to reach the category of “very high risk.”
A significant change is also projected in the wider Mesogeia area east of Athens, where risk is expected to rise by two levels, from low to high.
Kartalis stressed that assessing heatwave risk cannot be based solely on air temperature.
“Heatwaves are often associated exclusively with whether the air temperature exceeds a certain threshold for consecutive days,” he said. However, he added that modern scientific approaches go beyond temperature alone.
Measuring how vulnerable urban residents are
The CLIMASPIN project uses a range of indicators that connect the characteristics of a particular area, such as a city, with its climate conditions.
These include cooling degree days, the number of heatwave episodes, average maximum summer temperature, the number of “hot days,” defined as days when the maximum temperature exceeds 35 C, and “tropical nights,” when the minimum temperature remains above 25 C.
Vulnerability is assessed through a broader set of environmental, urban and social factors that determine how susceptible residents are to heatwaves.
These include ground surface temperature, which affects thermal comfort; vegetation levels; the percentage of built-up area; building height; distance from urban green spaces; the share of the population aged over 65; and access to health services.
“The temperature of an area alone is not enough. A series of factors that shape vulnerability must also be considered — in other words, how vulnerable a resident of an urban area is to a heatwave,” Kartalis said.
Athens neighborhoods facing higher vulnerability
The CLIMASPIN findings show that the highest current vulnerability levels, on a scale from 1, or very low, to 8, or very high, are concentrated across the wider Athens metropolitan area, with values ranging from 6 to 8.
Slightly lower levels are recorded in Elefsina and urban areas in the Mesogeia region.
However, the research also identifies areas where vulnerability is relatively low despite high heatwave risk.
Kartalis explained that this can occur when an area exposed to high heatwave risk also has substantial vegetation, a relatively low percentage of built-up surface, low or moderate building heights, short distances to green spaces or other factors that reduce residents’ vulnerability.
“This case, of course, seems ideal for Athens: the risk is high but vulnerability is relatively limited,” he said.
The research can also combine different indicators to identify areas where vulnerable population groups overlap with unfavorable environmental conditions.
For example, combining vegetation data with maps showing the population aged over 65 can identify areas where older residents are particularly vulnerable to heatwaves.
Green spaces can have a cooling effect that reduces the thermal discomfort experienced by residents, Kartalis said.
He identified neighborhoods in Kallithea and Galatsi, as well as central Athens, as examples where a relatively large population aged over 65 coincides with limited vegetation.
Such information could be important for both urban planning and the health care system, he said.
Mapping vulnerability at the neighborhood level
The methodology is designed not only to document heatwave risk but also to help authorities plan targeted interventions.
Kartalis said adaptation and resilience measures should not be based solely on differences in air temperature, but should also take heatwave risk and vulnerability into account.
For example, if an area has low or moderate vulnerability because buildings are relatively low and the built-up area is limited, this could indicate that high-rise buildings in dense configurations should be avoided.
If vulnerability is high because vegetation is limited and residents have to travel long distances to reach green spaces, increasing greenery and, particularly, distributing green spaces across an area should be a priority.
Vulnerability is analyzed on a 100-by-100-meter scale, effectively allowing assessment at the neighborhood level and targeted spatial interventions across about 100 cities in Greece.
The project provides information for areas throughout Greece and can be used to identify where vulnerable population groups and adverse environmental conditions overlap.
Climate adaptation plans should cross city boundaries
Kartalis said one of the most important findings of CLIMASPIN is the combined mapping of heatwave risk and vulnerability across the wider Athens metropolitan area.
He argued that Greece needs climate adaptation plans that do not stop at municipal boundaries.
“These plans should not be based only on temperature and should not be separate for each municipality — something that limits their effectiveness, since heatwaves do not recognize borders,” he said.
Instead, he said, plans should be coordinated by a central body so that municipalities can work together and improve their effectiveness.
According to Kartalis, such plans have been significantly delayed, with only a few exceptions.
Linking urban planning to climate change
The research also highlights the need to connect urban planning directly with climate change considerations.
Kartalis pointed to recent discussions over allowing an additional floor on buildings as an incentive for bioclimatic interventions, arguing that the project’s findings demonstrate how vulnerability to heatwaves can increase when taller buildings are constructed in densely built areas.
“When it is ignored, the result is that the microclimate of these areas deteriorates and residents become more vulnerable,” he said.
The CLIMASPIN project was coordinated by the National and Kapodistrian University of Athens, with the participation of the University of Thessaly, the Thymios Papagiannis and Associates planning office and geoinformation company GET.
The project was implemented under the “Research Excellence Partnerships” program of Greece’s National Recovery and Resilience Plan, “Greece 2.0.”
