Introduction
According to scientists, climate change will result in more frequent and extreme weather events such as summer heat waves. These effects will be exacerbated in urban areas where concrete and pavement re-radiate heat. In addition, urban areas must also cope with air quality problems, which are expected to worsen in coming years. Therefore, we need to develop where possible adaptation strategies to deal with climate change.
Toronto Public Health, the
Clean Air Partnership and the
Toronto Atmospheric Fund (TAF), with the financial assistance of
Government of Canada Climate Change Action Fund (CCAF), have embarked on "Cool Toronto", a special project that will develop model municipal practices and policies that will help protect Torontonians from the adverse impact of summer heat.
An advisory committee of leading Canadian climate scientists, City of Toronto decision-makers, health and environment experts has been established to advise on project implementation.
The project has three parts:
Part 1: A Heat-Health Alert System
Increasing temperatures pose significant risk to the health of Toronto residents.
These include:
- Heat-related illness and mortality during heat waves, especially for seniors;
- Exacerbation of pulmonary disease due to concentrations of ozone and particulate matter;
- Increased risk of certain infectious diseases, such as encephalitis, which spread more readily in hotter weather.
A Heat-Health Alert System, tailored to Toronto's unique climate, provides public health officials with a 48-60 hour warning before a potentially lethal air mass is predicted to arrive in the city. Toronto Public Health uses this system to implement emergency response plans based on the estimated number of Toronto residents, especially seniors, at risk of illness and death. In addition, the City of Toronto is a participant in the United Nations Showcase Project to develop this system worldwide for vulnerable cities.
Part 2: Longer Term Adaptation Strategies
The project also provides better scientific understanding of Toronto's heat island and the benefits of mitigation strategies. Dark surfaces and infrastructure present in the city amplify the heating capacity of incoming solar radiation. Over the long term, municipal policies and measures that encourage urban reforestation and more reflective roofs and streets can cool ambient air temperatures. The result? More healthful micro-climates for people, reducing the hot air that air conditioning pumps into the urban environment, and ameliorating heat induced smog levels.
Part 3: North American Urban Heat Island Summit
May 1 to 4, 2002
The Summit has allowed scientists working on this issue in Canada and the United States to provide up-to-date results of their research and to network with each other. In addition, municipal government leaders from both countries have presented case studies and best practices and policies.
The Heat Island Summit:
- Provided status on the latest research;
- Explored how research can inform policy and practices designed to reduce and respond to extreme summer heat;
- Identified challenges and barriers, as well as best practices;
- Examined methods of addressing urban heat island and health issues.
The Urban Heat Island - what is it?
Heat islands develop in cities as naturally vegetated surfaces are replaced with asphalt, concrete, rooftops and other manufactured materials. The artificial materials store much of the sun's energy and remain hot long after sunset. This produces a dome of elevated temperatures over a city that are significantly higher than air temperatures over adjacent rural or suburban areas.
Other aspects include:
- During the night, the stored heat energy in roads and other structures is slowly released into the air keeping cities warmer than rural areas at night.
- Tall buildings also block infrared radiation from escaping and further slow the cooling process.
- Vehicles, factories and air conditioners add more heat to the atmosphere and further enhance the heat island effect.
Is this a negative thing?
Yes! Heat stress is a killer. Higher ambient air temperatures exacerbate heat waves. Higher temperatures also speed up the chemical reactions that produce smog. This in turn increases suffering by people with respiratory problems, and increases health costs.
In addition, the warmer a city is in the summer, the more demand there is on electricity through the use of air conditioning. Energy costs go up, and to meet growing demand, power plants must increase their use of fossil fuels, which negatively impacts air quality and leads to climate change.
What can we do to counteract it?
We should promote the use of cooler surfaces and shade trees.
- Cities can be cooled by strategically placed vegetated areas. Trees and other vegetation can shade buildings, pavements, parking lots and roofs, and naturally cool a city by releasing moisture into the air through evapotranspiration.
- By protecting buildings from wind, trees can reduce heating costs in winter, and through direct shading and evaporative cooling, can contribute to reductions in air conditioning use in summer.
- The use of reflective surfaces such as light-coloured roofs, roads, and parking lots are another way to cool cities. Light-coloured surfaces reflect rather than absorb heat. The more solar radiation a surface absorbs, the hotter it gets. The more radiation it reflects, the cooler it stays, and cooler surfaces can be achieved with little or no additional costs.
Strategically placed vegetation and the use of reflective surfaces will not only help cool cities during summer months, but also lower energy bills by reducing energy use (a hot roof translates into much higher air conditioning costs). This in turn reduces greenhouse gas emissions and ultimately improves air quality.
What is the link between the Heat Island Effect and Air Quality?
Smog is a photochemical reaction of nitrogen oxides (NOX) and volatile organic compounds (VOCs). NOX and VOCs react in sunlight and produce smog. The reaction rate is highly temperature sensitive. By lowering ambient air temperature, it is possible to slow the process of smog formation and improve air quality.
Why should I make efforts to combat Toronto's Urban Heat Island?
We need to develop adaptation strategies to address the impacts of climate change. According to scientists, climate change will result in more frequent and extreme weather events such as summer heat waves. These effects will be exacerbated in urban areas, where concrete and pavement re-radiate heat. In addition, urban areas must also cope with air quality problems, which may worsen in coming years.
It is a win-win situation: by reducing the effect of the Urban Heat Island, we have cleaner air; cooler, more comfortable temperatures in the summer; and we save energy as well as money.
So... let's COOL TORONTO!!!
For more information, please contact:
The Cool Toronto Project
cap@tafund.org
Tel: 416-392-6672
With financial assistance from the
Climate Change Action Fund
(CCAF)
