Feeling the heat? Here’s how cities are fighting the Urban Heat Island effect

There’s a good reason why Canadians like to escape the city during the sweltering summer months.

So, why are cities so hot? It’s called the urban heat island (UHI) effect. Built surfaces, such as roofs, paved roads, and parking lots, absorb large quantities of heat from the sun resulting in higher surface and air temperatures. The average air temperature of a city with 1 million people or more can be 3°C warmer than surrounding areas. In the evening, the difference can be as high as 12°C.

Warmer temperatures aren’t just uncomfortable — extreme heat is a serious health risk to Canadians, according to a 2020 report from the Government of Canada, which points out that health impacts from high temperatures are already being felt across the country.

With more than 82% of Canadians currently living in cities, and this number only growing, urban communities need to use innovative methods to combat and mitigate the urban heat island effect. Here’s how they’re doing it.

Attention from local governments

Some of the biggest impacts can come from local governments, where municipalities can use a suite of planning tools to implement actions to reduce urban heat islands.

Cities around the world have even appointed Chief Heat Officers to lead communities in adapting to extreme heat. In Montreal, the Government of Quebec has been implementing financial incentive measures to reduce UHIs. This includes an initiative to green the city’s East End, an area identified by the city for its high proportion of low-income residents and lack of green space.

Regional municipalities like Peel have been creating plans to ensure its services, operations and infrastructure are resilient to the impacts of climate change.

“As the temperatures increase and neighbourhoods continue to warm, the risk of more frequent or extended extreme heat events rise,” points out Christine Tu, Director, Office of Climate Change and Energy Management, Corporate Services, Region of Peel.

To help cities better understand areas with greater exposure to extreme heat, Evergreen has developed AI for the Resilient City, a data visualization tool that lets municipal stakeholders see which areas of the city are most impacted by UHI, compare that same data across years, months and a variety of in-depth metrics and use this information to plan for a more climate resilient future, while protecting those communities who are the most vulnerable.

“The urban heat data visualization tool can inform the Region’s response plan that aims to minimize the risk of heat-related illness especially in vulnerable residents,” Tu adds.

Using environmental and nature-based solutions

Though cities can’t simply remove all that infrastructure, there are a number of solutions to mitigate its heat-absorbing effects.

Roofs and pavements cover about 60% of urban surfaces, and absorb more than 80% of the sunlight that contacts them, according to the Government of Canada’s Urban Heat Islands Tools and Resources document.

But cool roofs and pavements can help reduce temperatures in buildings — and even entire cities.

In 2017, New York City began its NYC CoolRoofs program, offering paid training and work experience installing energy-saving reflective rooftops. In addition to helping stem the UHI, cool rooftops can reduce internal building temperatures by up to 30%.

But trees and vegetation around buildings and pavement is perhaps the most useful mitigation strategy. The urban forest lowers surface and air temperatures by providing shade and through evapotranspiration.

Planting trees is most effective when done strategically. As part of Vancouver’s Street Tree Cooling Networks, Simon Fraser University researchers developed maps to identify areas with a high number of people from populations vulnerable to heat, where actions to reduce UHIs, like tree planting, was needed most.

Deploying emerging technology

To maximize the benefits of nature-based solutions, communities will need to utilize emerging technology, according to Dr. Nadina Galle, a Canadian-based ecological engineer and technologist.

“Urban forests and ecology play a crucial role in stemming extreme heat, but nature is complex,” she says. “To maximize its cooling benefits, we need a better understanding of it.”

Galle’s research includes the Internet of Nature(IoN), a framework for deploying emerging technologies, such as sensors, satellite imagery, and machine learning, to protect and restore urban nature.

“An IoN network will support urban planners in developing an urban nature intelligence system that will improve the understanding of urban ecosystem dynamic.”

But beyond restoring urban nature, new energy technology is helping mitigate excess waste heat from highly populated cities.

A report from the Canadian Institute of Planners suggests that reducing the UHI effect “goes hand in hand with being energy efficient.” That report highlights thermoelectric technology and combined heat and power systems as methods to turn heat into a useable resource rather than releasing it into the atmosphere to further warm our cities.

Encouraging public participation

The placemaking process doesn’t end with municipal governments, builders and developers. Engaging communities through public art or environmental initiatives not only increases awareness of issues like the urban heat island, but also helps create innovative solutions.

It’s public participation that’s helping to drive Evergreen’s Climate Ready Schools pilot in Milton, Ontario. The revitalized school grounds will feature ecological services, accessible community green space, and healthy environments for play and learning. But an important component of the pilot is climate mitigation measures to combat the urban heat island effect.

“Thermal comfort was identified as a key design driver as we continued to host discussions about solutions to rising temperatures and the effect on the local environment,” says Heidi Campbell, Senior Program Manager at Evergreen.

Through a comprehensive participatory design process that engaged students, school staff, parents, and community members, the school grounds are being transformed into a heat-adaptive landscape.

“When we engage communities in a co-creative planning exercise, shared knowledge and experiences bring vibrancy to the discussion that drives innovative thinking,” Campbell adds. “This kind of process also builds a connection to place and helps to nurture a sense of belonging. The community has learned so much from each other during our process — this has been transformative not only for the landscape, but for the people who live in the community.”

Learn more

AI for the Resilient City was created with start up support from AI for Earth, a pillar of the AI for Good, Microsoft’s commitment to empower those working around the world to solve humanitarian issues and create a more sustainable and accessible world. The project has received further funding from the RBC Foundation through RBC Tech for Nature to help scale this program. In its next phase, AI for the Resilient City will enable the local Ontario conservation authority to create a baseline level of UHI for the Peel Region that will help demonstrate the relationship between infrastructure and vulnerable populations in the area.