1. Managing Environmental Problems and the Urban Microclimate
IB Geography II

2. Part 1

3. Close Reading Activity
“Cities Make Own Weather Due to Trapped Heat” from the National Geographic.
As you close read and annotate,
Use Context Clues to try and define “Urban Heat-Island Effect”
Answer: How do cities impact temperature? Find specific evidence that supports your answer.
Answer: What trends in temperature can we expect due to increasing urbanization?
Answer: How can trees be the solution?

4. The Brown Agenda
Environmental problems in urban areas vary over time as economic development progresses.
The greatest concentration of environmental problems occurs in cities experiencing rapid growth (such as Mexico City)
The Brown Agenda: the concentration of environmental problems. It has 2 main components:
Issues caused by limited availability of land, water and services
Problems such as toxic hazardous waste, pollution of water, air and soil, and industrial accidents.

5. Traffic Problems in LEDCs/MEDCs
Private car ownership is lower
Many cars are poorly maintained and high polluters
Heavy reliance on affordable public transport
Journeys are shorter but take longer
Less dependence on car, but growing.
MEDCs
Increased number of motor vehicles
Increased dependence on cars as public transport declines
Major concentration of economic activities in CBD
Inadequate amount of roads and parking
Frequent roadwork
Urban sprawl results in long trips to work.

6. Microclimate
The climate at a very local scale that influences the presence and distribution of organisms is known as the microclimate.
Mesa Verde: vernacular, passive solar, sun angles, thermal mass

7. Structure Of Air Above Urban Area
Greater amounts of dust particles in air.
There is less water vapor because water is removed quickly by drainage and sewers.
There is less vegetation to take in water and release it later, but more CO2 and higher proportions of toxic fumes due to fuels and discharge of waste gases by industry.

8. Structure Of The Urban Surface
More heat retaining materials with lower albedo (reflectivity).
Rougher surfaces, with a great variety of perpendicular slopes facing different aspects.
Tall buildings can be very exposed, and the deep streets are sheltered and shaded.

9. Albedo

10. Temperatures
Stronger heat energy retention and release, including fuel combustion, gives significant temperature increases from suburbs into the centre of built-up areas creating heat “islands”.
These can be up to 8 degrees warmer during winter nights.
Snow in rural areas increases albedo, thereby increasing the differences between urban and rural.

11. Urban Heat Island Effect
Urban areas are generally 2-4 degrees warmer than those in the surrounding areas.
This creates an Urban Heat-Island (UHI) or the Urban Heat-Island Effect
Its intensity is the temperature difference between the urban and the rural area.

13. Urban heat profile

14. Impact of Buildings
Tall buildings will give cooler temperatures at street level, as not as much radiation from the sun is able to reach it.
Short buildings will heat up the street level as it allows radiation to be reflected between buildings.
Buildings will also reduce wind speeds (so its warmer) or will channel them (so it’s very windy)

15. Question to Think About
Why does the urban heat island effect matter?
Consider:
Increasing rates of urbanization
Increasing affluence
Possible links to global warming
Positive feedback mechanisms- hotter cities create more heat.

16. Part 2

17. Socioeconomic Impacts of the UHI
Human Health: high levels of ozone, suspended heat cause serious respiratory problems for the elderly, sick, and children.
Human Discomfort: high levels of humidity, atmospheric dust, and poor air quality worsen the quality of life in cities for many
Disease: higher temps increase the likelihood of vector and waterborne diseases in poor cities.

18. Socioeconomic Impacts of the UHI
Energy Waste: high levels of energy used in air conditioning systems are an increasing concern
Heat Stress and Illness: working days are lost and productivity lowered
Environmental Degradation: Intense heat causes the degradation of urban fabric such as rubber and tarmac, creating long-term cost to city governments.

19. Factors Influencing Urban Heat Island Intensity
Weather Conditions: clear and calm with no wind intensify UHI
Topography/hydrology: inland cities far from water have higher UHIs
City population size and density: large population consumes more energy and generates more air pollutants
Level of economic development: developing cities have high density and high energy consumption, but weak emissions controls.

20. Factors Influencing Urban Heat Island Intensity
Building and Street design: narrow streets are cooler by day, but retain heat at night
Land Surface Cover: Concrete and asphalt have a high thermal capacity and absorb solar radiation during the day and release it as heat at night.
Anthropogenic Heating: moving or stationary traffic and air conditioning units increase UHI intensity
Air Pollution: causes heat retention and increases UHI intensity.

21. Why Do We Care About Heat Islands?
Heat islands can affect communities by
increasing summertime peak energy demand
air conditioning costs
air pollution and greenhouse gas emissions
heat-related illness and mortality
water quality.

22. High Energy Demand Increased energy consumption:
Higher temperatures in summer increase energy demand for cooling and add pressure to the electricity grid during peak periods of demand.
One study estimates that the heat island effect is responsible for 5–10% of peak electricity demand for cooling buildings in cities.

23. Increased Emissions
Elevated emissions of air pollutants and greenhouse gases:
Increasing energy demand generally results in greater emissions of air pollutants and greenhouse gas emissions from power plants.
Higher air temperatures also promote the formation of ground-level ozone.

24. Quality of Life Compromised human health and comfort:
Warmer days and nights, along with higher air pollution levels, can contribute to general discomfort, respiratory difficulties, heat cramps and exhaustion, non-fatal heat stroke, and heat-related mortality.

25. Water Quality Impaired water quality:
Hot pavement and rooftop surfaces transfer their excess heat to stormwater, which then drains into storm sewers and raises water temperatures as it is released into streams, rivers, ponds, and lakes.
Rapid temperature changes can be stressful to aquatic ecosystems.

26. What Can Be Done?

27. What Can Be Done? Green Roofs
A green roof is a roof of a building that is partially or completely covered with vegetation and soil
The term "green roof" may also be used to indicate roofs that utilize some form of "green" technology, such as solar panels
Cool Pavement
The term refers to materials chosen to reduce pavement temperature by increasing pavement reflectivity or controlling temperature by other means through choice of materials and engineering design
Construction of Previous Pavement
Pervious pavements can be made of concrete or asphalt, open-celled stones, and gravel, that are mixed in a manner that creates an open cell structure allowing water and air to pass through.

28. Advantages
Because pervious pavements allow rainwater to seep into the ground through the pavement:
Vegetation is watered, reducing the need for irrigation
Ground water is recharged
Water resources are preserved
Stormwater runoff is reduced
Stormwater runoff quality is improved

29. Question to Think about: Identify and describe TWO differences between urban and surrounding rural areas that contribute to the temperature differences between them.

30. Part 3
Urban Heatwaves

31. Urban Heat waves
A heat wave is a prolonged period of excessively hot weather, which may be accompanied by high humidity
A growing problem due to global warming.
They catch urban societies unprepared and unaware and can result in high mortality rates.
Increasing risk with urbanization and the rapid growth of megacities.

32. Heat Waves
In the United States, heat waves kill more people than all of the so-called “natural disasters” combined.
In Chicago, more than 700 people died during one week of 1995.
(4:18)

33. Paris Heat wave of 2003
(3:51)

34. Paris Heat wave of 2003 Close Reading Activity
Questions for Think-Pair-Share
Referring to Figure and 11.31, describe the patterns for day and night-time temperatures (describe general pattern over whole area for both maps and name and locate areas that have temperature anomalies)
Suggest reasons for the patterns you have found. (Hint- use evidence from Keys to help)