Heat Mapping, Urban Heat Islands

Mapping the temperature of the objects and buildings around your site can help students get a first-hand look at the Urban Heat Island Effect, and how our built environment can make hot days worse. Using IR thermometers students will create a heat map showing the temperature of different objects and surfaces.

Dense urban areas often build up the highest levels of heat, because of the sun absorbed by blacktop, pavement, and roofs, as well as the heat generated by cars and buildings (all use of electricity and other fuels generates some heat).

Green spaces, especially areas with trees, are generally the coolest areas. Urban heat islands are an environmental justice issue since the worst impacts often fall disproportionately on the very people who have the least economic access to air conditioning, or access to land on which they can plant trees or create new green space. As global climate change steadily increases the number of 90+ degree days per year, urban heat islands pose a growing public health risk.

Heat Mapping, Urban Heat Islands was developed as part of the Science of Sweat Workshop, including investigations of how sweat, and more generally evaporating water, can cool things down, and the impacts that extreme heat can have on our bodies. Designed for out-of-school-time educators, the workshop is easily adaptable to other educational settings. Topics include evaporative cooling, the water cycle (including the role of energy), urban heat islands, and staying cool while outdoors. These topics are relevant to spending time outdoors in the heat, they introduce environmental justice and equity issues, and they provide a hands-on introduction to widely taught science concepts.

Supplies per team:

• Pencil
• 3 colors of highlighters or markers (ideally red, yellow or orange, and blue or green)
• Clipboard and Paper
• Optional: printed base map
• IR Thermometer(s)

For rain version (indoor option) add for class:

• Plastic sheet or cut up plastic bag (approximately 4’ by 4’)
• Spray bottle with water
• Hairdryer, ideally with diffuser
• Small boxes (tea and cereal boxes)
• Construction paper, variety of colors
• Scissors
• Blue tape or masking tape
• Optional: Green sponges for model trees
• Optional: Printed squared paper for base maps

Note: IR (infrared) thermometers -- sometimes listed as non-contact thermometers, or “temperature guns” -- allow students to digitally measure the temperature of objects without touching the object. They are wonderful tools for science investigation and can be purchased for $10-$12 and up. Having several will allow students to work in small groups. Choose an IR thermometer that is designed for uses other than (or in addition to) checking body temperature. For example, an IR thermometer that is listed as useful for cooking, refrigeration, or swimming pools. Many models have a built-in laser pointer -- this is helpful for aiming the thermometer, and most models allow you to turn this feature off. You can find models without the laser feature if you are not comfortable that your students can use a laser pointer safely.

Students should work in teams (the number of teams may be limited by the number of thermometers you have). Each team should have at least one person with a thermometer, and one person to record the temperatures on the map. Each team will also need a clipboard, paper (or base map if you are using them), a pencil, and a set of highlighters. At some point in the activity, the recorder should switch roles.

You can assign each team to a different area -- try to pick areas in advance that will have a good variety of surfaces: ideally blacktop, buildings, garden, lawn, and trees. It does not have to be a large area.

The first task will be for students to draw a map of their area. Drawing a map is a great STEM skill, but if you do not have time, you can speed up the activity by using a preprinted base map. Locate the area on an online mapping service and choose satellite view, then print the map in black and white.

If students have not used IR thermometers previously, explain how they work. Make sure to decide if you are using Fahrenheit or Celsius, and show students how to change the setting in case it gets switched. (You may want to do the Tree Sweat, Bottle Sweat: Evaporative Cooling activity first.)

Be Safe: Many IR thermometers have a built-in laser pointer to help you aim the thermometer. Never point the laser into your eye, or into the eye of another person or animal.

Allow time for students to try out the thermometers and find the temperature of different objects around them, preferably in a sunny outside area.

Discuss what objects/surfaces they found that were hottest and coolest. Do they have theories about why? What was surprising?

Introduce the issue of Urban Heat Islands (see resources for possible videos), and explain that they will be working in teams to create a heat map of their area.

Explain that teams should start by drawing a sketch map of the area they will be surveying. The maps do not have to be very accurate but should show major features such as buildings, gardens, trees, roads, etc. Students can always add detail as they go.

If students already have a lot of theories about what areas are likely to be hot or cool, you can have them make predictions about what areas would be warmest, coolest, or in the middle. They should record their predictions on their map with dots of color (red=warmest, yellow/orange=medium, blue/green=coolest).

Once students have drawn their map, have them measure and record the temperature of all the surfaces they can safely reach in the area. For now, they should write the temperatures on their map (later they can go in and decide on ranges and colors). The activity will be most compelling on a warm, sunny day.

Students will quickly find what areas are similar or different in temperature. Participants in this activity have been surprised by how moving a few feet in one direction can make a big difference: for example a surface in the sun versus in the shade of a tree. Likewise, students have been surprised at just how hot some surfaces can become -- for example the black roof of a garden shed. The color of objects can make an unexpected difference too, for example, two cars may have very different temperatures, as can two types of pavement. Also, the direction surfaces are facing will have an impact.

The coolest areas are likely to be areas with plants and trees. This is both because of shading from the trees, and evaporative cooling (see Tree Sweat, Bottle Sweat: Evaporative Cooling).

Once students have recorded the temperatures, have the groups color their maps. You can get into interesting discussions about what range of temperatures should count as cool, medium, or hot.

Students may find additional variables to consider, for example, the maker of one of the maps above added notes about the color of each surface -- triggered by the discovery that the black and white cars had very different temperatures.

What did different groups find? What were the hottest and coolest areas? Were there surprises?

Do students think the area is well designed for heat? If they were architects or city planners, how might they redesign the area to be more resilient to extreme heat, and more pleasant to live in?

If the surrounding area is residential, what things are the residents in the area likely to be able to change to mitigate the impact of extreme heat? What would be hard for them to change? What would need to happen to give the residents of the area more power to improve things?

There are many ways to extend this activity:

• Are there small projects that students could plan that would help make the area more resilient to extreme heat, and safer and more pleasant on hot days?
• While mitigation is part of the solution, any long-term solution also needs to address global climate change. Any projects that reduce energy usage will have a long-term positive impact on climate change and will help the problem of extreme heat in the long run.
• You may be able to join a citizen science project that focuses on climate change (see resources section).
• Many cities have tree-planting programs or other initiatives you may be able to tap into.
• Does your city have a Climate Change Vulnerability Assessment? These reports have detailed maps showing potential climate impacts, as well as maps of the most vulnerable (Environmental Justice) communities (e.g. low income, limited English proficiency, elderly). Overlaying these maps can show where the burden of the impacts will be felt.
• See how your heat maps change at different times of the day. Not only do different surfaces absorb different amounts of heat, but different materials also hold heat for longer. While the heat island effect is driven by the sun, the effects can last into the night.

If you need to do this activity on a rainy day, or you want to explore an indoor model of the phenomena, you can build a model city.

Tape a plastic sheet (approximately 4 x 4 ft) on the floor.

If you want to make mapping easy, pre-cut a number of equal-sized squares of construction paper (each approximately 6” x 6”): black for streets, and green for grass or parks. Cut some light blue shapes for water (ponds in the park, splash pads, etc).

Have students arrange the construction paper squares to start forming a city map, with streets, parking lots, residential areas, and parks. Tape down the squares.

Add an assortment of small boxes for buildings (tea boxes and cereal boxes work well). Use more construction paper to make different color roofs for the buildings. You can also make green construction paper trees, or use green sponges to make model trees.

Lightly spray the green (park and grass) squares and any sponges you are using with water so they are moist. Remember plants are always transpiring water (see Evaporative Cooling: Tree Sweat, Bottle Sweat. Spray the blue (water, sprinkler, splashpad) shapes heavily with water.

Have teams use squared paper to draw maps of the city.

When you are ready to do your heat survey, hold a hairdryer (with the diffuser attached), about 6ft over the map -- ideally, it will be high enough to provide a fairly even flow of heat and wind. If you have sun, you can also build the model in the sun.

Proceed as above, having teams record the temperatures for each square, and then color-code their maps.

Heat in the city - a short video from Wisconsin PBS featuring spoken word artist Elijah Furquan:

Wisconsin, Extreme Heat

Metropolitan Area Planning Council, short article on heat islands around Boston:

https://www.mapc.org/planning101/mapping-the-heat-...

EPA Urban Heat Islands information bank:

https://www.epa.gov/heat-islands

See the Urban Heat Island Compendium section on the EPA page for detailed information on heat island formation, contributing factors, and links to even more resources:

https://www.epa.gov/heat-islands/heat-island-compe...

Citizen Science Projects:

Citizen science projects recruit volunteers to work on research projects with scientists. Some can accommodate school or other groups. At any given time there are usually a number of active projects that involve climate change.

For an example see:

https://research.noaa.gov/article/ArtMID/587/Artic...

To find listings of current projects, try:

https://scistarter.org/ or https://scistarter.org/

This work is made possible by support from STAR, a Biogen Foundation Initiative. The team at Lesley supporting this initiative includes faculty and staff in the Lesley STEAM Learning Lab, Science in Education, the Center for Mathematics Achievement, and other related Lesley University departments and programs.