In dealing with climate change we need to take the heat out of our cities:
Renewable energy sources, energy efficient design, fossil fuel purification, electric vehicles and carbon reduction are all necessary measures when talking about environmental sustainability.
However, these measures are all focused on reducing greenhouse gas concentrations. They do nothing to address the massive amount of heat stored in, and emitted from, our urbanized lifestyles. This nefarious process occurs in every city on the planet – inevitably impacting on regional climates and subsequently on the global climate. But solutions to it have largely been absent from conversations about climate change.
If we can figure out how to remove this thermal pollution, then the climate-changing toxicity of greenhouse gases is rendered relatively innocuous.
Huge concentrations of these gases are already replete in the atmosphere and are very long-lived. So even if we miraculously stopped emitting all thermally sensitive gases, the global climate will continue to warm and be increasingly disrupted for at least the next 100 years.
Get the heat out
The only reasonable and timely remedy is to take the heat out of the equation.
A range of challenging consequences emerge from not moderating thermal pollution. Hundreds of thousands of massive hotspots are generated in the global climate system with extreme urban-climate weather events visited upon cities. Excess heat also impacts negatively on the general health, wellbeing and comfort of citizens. It is lack of relief at night, rather than high daytime temperatures, that puts people at most risk from heat stress.
Moreover, a significant quantity of fossil-fuelled energy is expended to cool buildings and vehicles to mitigate the negative effects of this thermal effect.
The major culprit in this thermal pollution equation is the “designed environment” – or the way a city is built.
In principle, medium-density, mid-rise cities with good sky-views set on narrow labyrinth street grids that shade and ventilate more naturally, help moderate heat excess. Massive high-rise canyon-cities, set on wide, dark, right-angle roads and concrete sidewalks, excessively trap and emit heat.
Whatever the form of a particular setting, there are hundreds of elements in the designed environment that are involved, each absorbing and emitting heat, in a never-ending cycle, from dawn to dusk to dawn.
You can download a study conducted in Victoria Park, Sydney using an infra-red thermal camera, rendering these otherwise invisible elements visible, here [The link will download it]: https://cityfutures.be.unsw.edu.au/documents/36/Final_Report_Hassell.pdf
The principle is simple. When the atmosphere is warmer than the elements in the designed environment, they absorb some of that warmth. When they are radiating at higher temperatures than the ambient air, they transfer some of their heat to it. From the measured infrared imagery from a study in Sydney, you can see the differences between elements and their maximum and minimum temperatures over 24-hours.