Urban areas experience higher temperatures than surrounding areas due to the urban heat island effect, primarily caused by solar heat absorption in dense city centers and waste heat from human activities. This phenomenon exacerbates energy consumption for cooling, contributes to increased smog due to higher temperatures, and can lead to extreme weather impacts. Effective urban planning that considers building materials, spatial design, and vegetation is essential for mitigating these effects and enhancing climatic comfort.

1. URBAN CLIMATES Urban areas can become several degrees warmer than the surrounding countryside. This phenomenon is known as the Urban Heat Island effect.

2. URBAN CLIMATES The main cause of urban heat islands is solar heat that is stored in the surfaces of dense city centres. In the countryside vegetation has cooling properties. City center Fields Forest park suburb

3. Waste heat from human energy use is also a significant factor according to season and the local population’s pattern of energy use, - eg. for transport, heating and cooling. City center Fields Forest park suburb

4. Urban Heat Islands can increase the effect of extreme weather phenomena. In the 2003 heat wave an estimated 35.000 people died across Europe from heat related illnesses. NASA: European Heat Wave 2003

5. The intensity of Urban Heat Islands vary dependent on a city’s location. In London it ranges from 1-6 degrees. Atlanta shows differences of up to 18 degrees. NASA: Atlanta Urban Heat Island

6. Urban heat islands increase the energy consumption for cooling. Energy used for cooling is among the main factors of the 40% of worldwide energy used in buildings. NASA: Atlanta Urban Heat Island

7. Urban heat islands increase smog in the local atmosphere of cities. Higher temperatures increase the chance of photochemical reactions of pollutants. NASA: Atlanta Urban Heat Island

8. During winter in cool climates Urban Heat Islands can be caused by waste heat from human energy use. Inadequately insulated buildings lets heat escape to the atmosphere. Copenhagen. January 24th 2009. Air temperature 0 degrees.

9. The narrow streets of the city center create relatively warm microclimates, since the heat can only slowly get carried away by wind or radiate out. Copenhagen. January 24th 2009. Air temperature 0 degrees.

10. Open spaces let more heat escape due to wind chill. In cold and windy weather these urban spaces offer less comfort for outdoors activities, including walking and riding bikes. Copenhagen. January 24th 2009. Air temperature 0 degrees.

11. The shape of the urban spaces create microclimatic zones according to their properties of shelter from the weather conditions, and offer different conditions for urban life. Copenhagen. January 24-26th 2009. Air temperature 2-3 degrees.

12. As weather changes from cold to warm, the climatic differentiation of urban spaces become more marked. Activities change according to daily and seasonal rhythms. Copenhagen. April 25th 2009. Air temperature 18 degrees.

13. The role of buildings in creating heat islands depend on the shape of the urban spaces they create and the thermal and radiative properties of surface materials. Copenhagen. April 25th 2009. Air temperature 18 degrees.

14. As air temperatures rise to 18 degrees during the day, the surface temperatures of the dark roof shingles rise to more than 45 degrees in less than 3 hours. Copenhagen. Sunrise April 24th 2009.

15. As air temperatures rise to 18 degrees during the day, the surface temperatures of the dark roof shingles rise to more than 45 degrees in less than 3 hours. Copenhagen. Sunrise April 24th 2009.

16. Knowledge of how to create climatic comfort using the building materials’ properties, transmissivity, conductivity, emissivity and heat capacity is crucial to low energy design. Copenhagen. Midday April 26th 2009.

17. Knowledge of how to create climatic comfort using the building materials’ properties, transmissivity, conductivity, emissivity and heat capacity is crucial to low energy design. Copenhagen. Midday April 26th 2009.

18. Heat builds up in tarmac pavements and building surfaces. Plants create cooler environments by casting shadows and by evapotranspiration – they “sweat”. Copenhagen. Midday April 26th 2009.

19. Heat builds up in tarmac pavements and building surfaces. Plants create cooler environments by casting shadows and by evapotranspiration – they “sweat”. Copenhagen. Midday April 26th 2009.

20. As the direct radiation from the sun diminishes, the heat stored in the buildings’ materials is slowly transferred to the air. The “afterglow” lasts all night. Copenhagen. Sunset April 26th 2009.

21. As the direct radiation from the sun diminishes, the heat stored in the buildings’ materials is slowly transferred to the air. The “afterglow” lasts all night. Copenhagen. Sunset April 26th 2009.

22. Creating comfortable, delightful urban environments requires attention to solar orientation, wind patterns, building geometry, materials and vegetation. Copenhagen. Afternoon April 26th 2009.

23. Creating enjoyable opportunities for life.

24. Thermographic cameras were provided by Miljøpunkt Indre By – Christianshavn www.a21.dk Precision Technic Nordic www.ptnordic.dk Thanks URBAN CLIMATES

25. Thermographic studies by Peter Andreas Sattrup Royal Danish Academy of Fine Arts School of Architecture URBAN CLIMATES