Hot weather in Danish cities can feel unbearably warm, even if thermometers show a relatively moderate figure in degrees Celsius.
While the design of Danish buildings – think large windows, good insulation for the winters – are known to be a major factor in this, the layout of the city itself is also in play.
“The features of cities (including Copenhagen) that make the city vulnerable to heatwaves are the high amount of dark paved surfaces and dark roofs as well as the lack of green areas and trees. It is a common challenge in many dense cities,” Camilla Hvid, Head of Sustainability with engineering consultancy company Sweco Denmark’s Department of Water and Climate, told The Local.
“Dense cities with many dark surfaces and few trees have a low albedo, which means that the surfaces absorb a high amount of the radiation from the sun and retain the heat,” she explained.
That is illustrated by differences in surface temperature measurements of up to 12 degrees between central district Vesterbro and surrounding suburban areas outside of Copenhagen, Hvid said.
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Sweco recently investigated how a number of different European cities, including Copenhagen, could build heatwave resilience as climate change looks likely to increase their frequency.
In Copenhagen, the number of heatwave days per year is expected to increase by 160 percent by 2100.
It should be noted that building and city design are not alone in making Danish cities feel hot – weather conditions are frequently humid, which can exacerbate the effect of the heat.
Humidity in Denmark can be up to 80-90 percent, Hvid said.
“The humidity is created by the moisture that comes over the country from the coasts, which is why the humidity is high in Denmark,” the senior engineer said.
“High humidity combined with heat makes it difficult to get rid of the body’s excess heat. That is why temperatures of over 25 degrees can feel severe in Denmark, and when temperatures rise to over 30 degrees combined with high humidity, it can be decidedly dangerous for the elderly and children,” she said.
While Copenhagen has its fair share of parks, more green spaces are the way forward for Danish cities that want to reduce the impact of increasingly frequent heatwaves.
“Part of the solution is to think of more blue and green spaces in our cities – more parks and plants, more water, more trees. Trees create shade, increase humidity, and help lower the temperature in the city,” Hvid said.
“But we can also do a lot by choosing and designing with light materials when we plan or transform the city, both when designing facades, roofs, and pavements – for example by replacing black roofing felt with white or chose a light material for the pavements,” she said.
“But in general, design the cities with more green areas and trees and incorporating green roofs and facades where possible.”
Hvid said that, as heatwaves become more frequent, the renovation of the existing cityscape and the establishment of new districts must take the heat into account and incorporate several elements that create a cooling effect.
“For example, in Sweco, we have helped Odense Municipality to map how future higher temperatures will affect the municipality,” she said.
“We have mapped heat-related challenges and identified areas of intervention where vulnerable groups are particularly exposed, and provided recommendations for measures to minimize the consequences of a heatwave,” she said.
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