Tag: Climate Change

Can Peterborough Beat the Heat?

This article was originally published on June 19th in Kawartha Now. A link to the original article can be found here: https://shorturl.at/gehv6

When discussing the greatest climate change risks facing the city of Peterborough, many people in Peterborough will think back to the floods and storms that our community has experienced over the past few years, but one more sinister risk for many of our city’s most vulnerable might simply be extreme heat.

Recently, there’s been dialogue among local public health experts and municipal staff about the impact that the urban heat island might have on our city, and the implications I believe are worth discussing.

In 2021, I created a map (below) that explores the deviation from the average temperature across all of Peterborough during a typical hot day in August. In that map, we can see the urban heat island at work. A review of the map reveals the downtown core, Lansdowne Street, the Townsend neighbourhood, and several newer subdivisions all clearly have much higher surface temperatures than nearby neighborhoods.

In the simplest terms, the lack of tree cover exposes hard surfaces such as concrete and asphalt to the sun, which then radiates the absorbed heat back out into the local environment. Neighbourhoods with more trees and less asphalt generally fare better than those without.

Tree cover is one major factor contributing to urban heat, but there are other trends revealed by this map that are worth exploring.

Worth noting is the income disparity that is highlighted by the urban heat island effect. Neighbourhoods with lower incomes, such as Townsend Street or the Tallwood Towers neighbourhood, experience much higher average temperature deviation from the average across the city. The temperature difference can be as much as 15°C in some neighbourhoods.

An average temperature increase of 15°C could place some neighbourhoods in what is known as a dangerous “wet bulb event.” This could all be happening at the same time as other neighbourhoods in the city are experiencing hot, but not life-threatening, temperatures.

If you’ve never heard of a wet bulb event, it is when there is sustained increase in temperature and humidity to the point that the human body loses the ability to effectively regulate its temperature. Exposure to these conditions can lead to death in as little as six hours for those who are unable to move to a colder climate-controlled space or find other means of cooling off. Wet bulb events can actually occur as low as 31°C if humidity is above 95 per cent.

In the city of Peterborough, this could practically mean that individuals who live in lower income neighbourhoods, who are less likely to have access to air conditioning and more likely to have mobility challenges, could have a highly increased risk of extreme heat exposure. With a 15°C surface temperature difference across the city, this could conceivably be happening while citizens in other neighbourhoods are perfectly fine.

Comparing average income versus mean surface temperature across our city demonstrates a slight trend towards lower-income neighbourhoods experiencing an increased chance of facing increased temperature.

The trend demonstrated by this relationship is strong, but not absolute, so there must be other factors to consider when discussing urban heat island effects, and indeed there are.

As we explore those factors, we will discover potential strategies to mitigate the impact that the urban heat island will have on our community into the next century.

The Answers are Blowing in the Wind

If you’ve lived in the city of Peterborough long enough, you’ll be aware that the wind often blows from the west. These prevailing winds can help us understand some of the heat distribution in our city.

Remember that parks and greenspaces often experience lower-than-average temperatures than areas of concrete and asphalt. Let us consider what happens as the wind passes over these greenspaces. If the temperature of the air is warmer than the surface temperature of a tree that it is passing through, the wind will transfer some of the heat out of the air and into the leaves of the tree.

Each individual tree has an absolutely enormous surface area made up of leaves. This large surface area translates into a huge capacity to exchange heat out of the atmosphere. Neighbourhoods downwind of trees are well positioned to reap the benefits of these massive “heat exchangers,” as the cooler air now has increased capacity to absorb heat from the neighbourhood and convey it away.

This “heat exchanger” effect makes parks and greenspaces are some of our best tools for fighting the effects of urban heat and climate change. It is definitely worthwhile to consider park and greenspace planning strategies in our community that prioritize planting and protecting trees that are upwind of high-risk neighbourhoods.

As far as I am aware, little consideration has been given to this strategic factor when considering our urban forestry plan, and I would like to encourage leaders across our city to keep in mind.

Southern Exposure

South-facing slopes can also increase the risk related to heat exposure. Heat that radiates from the sun is more directly absorbed into the concrete faces of buildings and parking lots, especially those that face south.

Large parts of Peterborough are located on a southeast-facing slope. Ten thousand years ago, this large slope was the shoreline of glacial Lake Peterborough, and today offers stunning views of the surrounding countryside. These stunning views carry some risk exposure as well.

“South facing slopes can massively increase the risk related to heat exposure. Heat that radiates from the sun is more directly absorbed into the concrete faces of buildings and parking lots. “

The most pronounced exposure to the south is arguably the slopes north of the Parkway Trail on the north side of town. We can clearly see on the urban heat island map a line of census areas that experience higher than average temperatures, possibly due to this southern exposure.

Considering this, it may be worthwhile to prioritize south-facing slopes for naturalization and tree-planting measures across our city. I can already think of several possible locations that may be worthwhile to consider putting some effort into reforestation.

A (Cool) River Flows Through

Many people each summer make the trip down to the Silver Bean in Millennium Park along the shores of the mighty Odoonabii (Otonabee) River. It’s been unofficially dubbed “the little cottage in the city” and for a good reason. The natural surroundings create a welcome retreat from the urban heat radiated from the nearby downtown.

We should consider that the rivers and waters flowing through our city may be one of the greatest tools we have when fighting urban heat. As you take a moment to review the heat map, notice that much of East City is cooler than the west bank. I would argue that, in part, that is due to the downwind impacts of the river.

An image of people standing on top of a covered creek.

“Uncovering Jackson Creek is one of Peterborough’s greatest opportunities for climate change adaptation”

As wind blows across the river, it deposits warmth from the air into the water to be conveyed away from the city, therefore cooling the city’s east bank — just like a giant natural air conditioner.

This principle combined with several of the other watercourses in our city could provide huge benefits to neighbourhoods badly in need of heat interventions.

Jackson Creek in the Townsend neighbourhood and downtown has been almost entirely covered by buildings and parking lots. A long-term strategy of opening up the creek and naturalizing its shoreline could help keep these neighbourhoods cool, while providing recreational and flood-reduction opportunities.

Other creeks in our community are worth highlighting due to many of the same reasons, including Bears Creek in the north end of our city, or the hidden Brookdale creek roughly following Downie Street.

Urban heat is worth taking seriously. I hope some of you readers can take the time to incorporate some of these ideas into your work or encourage others to do so. Perhaps with your help, we can start to incorporate some of the above ideas into our urban planning strategies and help build a cooler, healthy, and vibrant community for everyone, no matter who they are or where they live.

Is Your Neighborhood The Hottest In Peterborough?

On August 15th 2021 it was 23.9°C at the Peterborough Municipal Airport. By all respects, an average summer temperature. If you looked at a thermometer outside your house though, it might paint a much different picture. In the downtown core and areas along Lansdowne St. temperatures reached as high as 40°C. This represents over 15°C temperature difference! What is happening and how can it be stopped?

The urban heat island is a phenomenon we’ve long known about. It occurs when natural land cover such as forest or meadows are replaced with surfaces that retain heat such as asphalt, concrete or pavement. These surfaces then radiate the heat back out into the local environment, warming the surrounding area. The effect can increase the cost of heating, and put elderly or other vulnerable citizens at risk of heat stroke, and even death.

The urban heat island effect often puts the most vulnerable populations at risk. Some of Peterborough’s lowest income census areas have the highest recorded temperatures. You’ll notice on the map that areas directly south and north of the downtown which are characteristic as lower income neighborhoods, have some of the highest recorded temperatures, while some of Peterborough’s more affluent neighborhoods have much lower recorded temperatures.

Image #1 characterizes a neighborhood south of downtown. Census Canada considers between 35% and 43% of the population to be low income. This neighborhood is one of the hottest in Peterborough, coming in at a 15°C temperature deviation. Meanwhile Monaghan Ward represented in image #2 only recorded a 5°C temperature deviation. It is clear that land cover and tree canopy have a huge impact on temperature deviation. With the additional pressure of climate change, these deviations are likely to become more pronounced over time.

What can be done about urban heat though? Luckily we have some solutions! Planting trees is once again, a major winner in this regard. Not only does tree planting decrease average temperatures, it can lower heating and cooling bills year round for residents, overall a huge win for the climate. Removing asphalt and other “high heat” surfaces can also benefit neighborhoods, replacing asphalt with grass is even a viable solution for combating urban heat. Depave projects around the country have made major inroads in this regard, and perhaps focusing on lower income neighborhoods could have an additional impact.

In all, reducing the urban heat island effect gives us one more incentive to restore ecosystems, plant trees, and protect our natural areas. Perhaps years from now, when you look at the thermometer outside your house, it may more accurately reflect the temperature across our city.

Data provided by USGS through LANDSAT 8.

A Little Toolkit For Confronting Climate Inaction

2019 was heralded as the year that ended climate change denialism. Enter a new era, where we must face a new threat: inaction on climate change.

Just over a week ago I published a short writeup on my twitter feed explaining how an enormous fountain in our town was an outsised contributor to greenhouse gas emissions in our city. This was due to the sheer volume of electicity used to power the monstrous pumps that spewed a steady stream of water 6 stories into the air.

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This New Sticker Drives Doug Ford Nuts

With the newly legislated carbon tax propaganda stickers, here at steward’s notes I decided to tell the real story (according to the Nobel prize winner this year)! These vinyl die cut stickers can be placed “at your discretion” anywhere you choose! Share with your friends and relatives! Head on over to the shop page and I’ll get your stickers in the mail ASAP. Profits will be donated to environmental charities in Ontario.

Its no secret, placing a price on carbon is the most simple and effective way to lower carbon emissions. Even Stephen Harper agreed while he was Prime Minister. The current plan is not perfect, but it is better than anything proposed by the Federal or Provincial Conservatives. This bumper sticker is nothing but a statement of the objective truth.

Sorry for the clickbait 🙂

What should Peterborough do in this Climate Emergency?

With the recent news of Kingston and possibly Guelph declaring a climate emergency, I began wondering what actions a city such as them or even Peterborough could do to begin the process of eliminating our climate emissions. Recently I came across the Drawdown proposal. It includes a list of 80 solutions that would reduce global emissions drastically while at the same time creating a better and more equitable future for humanity. All while creating a net global financial savings of nearly 50 trillion USD.

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