More than 3.5 degrees Celsius is estimated that the average air temperature in the greater Athens urban area may increase in the period 2041-2070 compared to the period 1971-2000, as a combination of the effects of climate change, based on the new scenarios, in particular the worst-case scenario of the United Nations Intergovernmental Panel on Climate Change, and the urban heat island.

This is the finding of a study by the National Academy of Sciences of the European University of Athens and the professor and member of the European Union’s Scientific Committee on Climate Change, Konstantinos Kartalis, as part of the CLIMPACT 2 research project. At the same time, it is noted that an increase of this magnitude will significantly worsen the thermal risk in Athens in the future period 2041-2070. The focus of the research is on thermal risk in Athens with the wider urban complex of the city categorised into five classes of thermal risk (very low, low, moderate, high and very high). Taking into account various parameters, the research also concludes that during the current period of time, the central areas of the wider urban complex of Athens as well as Piraeus and municipalities in its wider area, have a very high thermal risk, while the thermal risk takes the lowest values mainly in the areas in the northeast and east of Athens.

As Konstantinos Kartalis, professor of the University of Athens and member of the European Union’s Scientific Committee on Climate Change, stresses to the Athens-Macedonian News Agency, “in recent years, an increased frequency, intensity and duration of extreme weather phenomena has been recorded in the Southeastern Mediterranean region, with the effects of these phenomena also being reflected in Attica. These phenomena are mainly associated with very high temperatures and high temperatures. These recordings do not constitute a climatic peculiarity of Greece but essentially monitor global-scale temperature observations, which demonstrate a distinct global warming over the last 150 years due to anthropogenic interference. In addition, a particularly large number of heatwave episodes have been observed globally in recent decades, and these have also tended to be more frequent, longer lasting, and more intense. Typical examples are the heatwave episodes in Attica in 2022 and 2023, which combined high temperatures with long duration, which worsened thermal conditions in many urban areas.”

According to Kartalis, cities in general are particularly vulnerable to climate change as this adds to the Urban Heat Island (UTA) phenomenon, which is the fact that urban areas are warmer than neighbouring rural areas due to lower vegetation cover, stronger absorption of solar radiation and anthropogenic heat sources (cars, buildings, industrial and craft sources).

With the Urban Heat Island as a whole being generally stronger at night hours, as it is largely modulated by the slower cooling rate of urban areas compared to the countryside, the worst heat load and the highest energy consumption in buildings for cooling seems to occur during midday hours.

As Mr Kartalis underlines, a large number of studies by the University of Athens and other institutions in Greece have shown that climate change affects electricity demand. For example, it has been calculated that electricity demand in urban areas increases by 0.5 to 4.5% (depending on the study area) for each degree of air temperature increase. For Athens in particular, this increase in electricity consumption is in the order of 4.1% for a one degree Celsius increase in air temperature. Furthermore, according to Mr Kartalis, the thermal impact of the city is closely linked to a strong negative impact on the health of its inhabitants, particularly for the most vulnerable groups of the population. “The comparative study of daily mortality data from cardiovascular and respiratory causes in Athens led to the result that mortality of people over 65 increases in high and extreme temperatures by 20% and 35% respectively,”
he stresses.

As part of the CLIMPACT 2 research project, a project reported to the National Network for Climate Change and supported by the General Secretariat for Research and Innovation, the thermal risk in Athens was assessed by the National Research Centre of Athens using a combination of parameters such as surface soil temperature (LST), vegetation index and population density in relation to people over 65 years old. As a result, the wider urban complex of Athens was categorized into five (5) thermal risk classes: very low, low, moderate, high and very high.

As can be seen in the map below, the central areas of the wider urban complex of Athens as well as municipalities in Piraeus have very high thermal risk, while the thermal risk takes the lowest values mainly in the northeast and east.

At the same time, the temperature difference for the period 2041-2070 compared to the period 1971-2000 was also estimated using scenario SSP5-8.5, which is part of the new UN Climate Change scenario series and is the worst scenario (essentially assuming that the use of fossil fuels will continue unabated and therefore the concentration of greenhouse gases, and in particular carbon dioxide, in the atmosphere will increase further). In particular, for the assessment, as Mr Kartalis explains, three climate models were used, the results of which were mapped to an improved spatial scale of 12.5 km x 12.5 km, using machine learning and a number of predictive parameters such as the average surface solar radiation flux, wind speed at 10 m from the surface, etc.

As can be seen in the figure below, the temperature increase for the wider urban complex of Athens exceeds 3.5 degrees Celsius, as a combination of climate change and the urban heat island, with the exception of the coastal zones and areas north of Athens. It is reasonably estimated that an increase of this magnitude will significantly worsen the thermal risk in Athens in the future period 2041-2070.

“To identify solutions that will enhance a city’s resilience to climate change, you need to study it in depth, using ground and satellite data as well as the results of climate simulations. The CLIMPACT research project is an innovative research and synergy project between Universities and Research Centres in Greece. It essentially gives space to advanced research on the highly critical issue of climate change, helps to understand the complex atmospheric and climate processes and facilitates the development of innovative tools both for the mapping of climate impacts and, most importantly, the identification of the necessary solutions to enhance the resilience of Athens and other cities in Greece to high temperatures and heat waves”, notes Mr. Kartalis, Professor of Environmental and Climate Physics at EKPA.