On Tuesday morning, my girlfriend messaged me at 8am telling me how thick the London city air and how hot it already was. As she was messaging me that, I was sat outside in the countryside enjoying breakfast in the sunny weather with a cool breeze keeping everything comfortable.

We’re only about 50 miles away, so there isn’t too much variability in the weather, however, there was about three degrees of temperature difference on Tuesday and as much as five degrees difference today when temperatures are expected to reach record-breaking levels.

So why is there so much difference?

The Urban Heat Island

As we’ve become an increasingly urbanised species we’ve built huge concrete jungles to satisfy almost every need we have. However, the materials and way that these cities have been built have also made them almost insufferable during the hot weather. Add in the heat energy created by transport and huge numbers of people in a small area and it’s no surprise our cities are much hotter than rural areas that surround them.

The image below shows the Urban Heat Island Effect in London. The redder the area, the hotter that part of the city. In comparison, areas that are greener are almost ten degrees cooler. If you look towards the west of London, just south of the river, there is a patch of green surrounded by the darker oranges and reds that indicate higher temperatures; that area there is Richmond Park.


A similar image of New York City shows just how much warmer urban areas are compared to parkland and other green areas.


Factoring in the Climate Crisis

Based on the evidence of the climate crisis and models of how the planet will continue to warm without action, our cities are only going to get hotter.

The current heatwave that has smashed temperature records in The Netherlands, Belgium and Germany, and has also led to extreme heat in the UK. Although not quite beating the hottest ever recorded temperature of 38.5℃, much of the UK has sweltered with urban areas recording the hottest temperatures. Trains are running a reduced service in and out of London and the London Underground has recorded temperatures of 42 degrees!


Infrared Images were taken in the London Underground showing just how hot the Underground is


As the climate crisis creates hotter conditions during summer months, cities in the UK, Europe and around the world are going to become more and more difficult to live and work in. Our urban areas need a complete redesign with climate-sensitive considerations that will allow urban areas to remain livable as the planet continues to warm.

How Can We Reduce the Urban Heat Island Effect?

Realistically we aren’t all just going to leave cities. Nor can we tear them down and rebuild them quickly. What we need to do is adapt and redesign our cities. We can change what is currently being built and what will be built in the future to be more climate-sensitive as well as making even just small changes that can help make a city more livable.

1. Urban Greening

There’s a very simple reason why cities are also known as ‘concrete jungles’. The natural environment that once existed is replaced by highrise buildings and shopping centres with extensive green areas relegated to the urban-rural boundaries.

As shown in the heat maps above, parkland and areas of greenery are much cooler than typical city streets. If we’re able to bring trees along our streets, plants on the sides of buildings and just generally make our cities more green, the impact that would have on cooling streets and making them much cooler would be huge.

Increasing the amount of greenery and trees in our urban areas not only helps cool city streets but also reduces air pollution. CO2 and other greenhouse gases are absorbed by trees and plants, cleaning the air and reducing the pollutants emitted by cities. Whilst it would take a lot of urban greening to get there, planting trees and shrubs can help a city become carbon neutral.

2. Better Construction Materials

Concrete and tarmac that are perhaps two of the most common materials in our cities, yet the amount of heat they absorb and radiate is staggering. By choosing materials that don’t absorb as much of the heat as concrete, less heat will be radiated onto the city streets, helping us stay cooler even during the very hot temperatures we’ve seen today.

Glass can look very attractive on the outside of buildings but it reflects and refracts light and heat all across the city, in many cases reducing the impact of any shade that is produced by concrete buildings. I’m not at all saying get rid of glass on buildings – that’s just not practical in any way whatsoever – but not covering the entire building in glass would certainly have a positive impact.

In cities and in suburbs, dark roofing often covers the majority of housing. In a similar way to concrete and tarmac, dark roofing absorbs heat and radiates it into the environment, creating even hotter temperatures. Just choosing to have white or lighter roofs can help reflect light and heat away from city streets whilst also stopping the buildings they cover from being even hotter on the inside.

3. Reduce Private Transport

One almost constant feature of cities around the world is traffic in city centres. Doesn’t matter where you go, no city has free-flowing traffic no matter the size of the highway built. All that traffic and the idling engines create huge amounts of heat in cities. If you’ve ever walked behind a vehicle with the engine running you’ll know the heat that comes from it.

Replacing all those private vehicles with public transport or encouraging people to walk or cycle would have a dramatic effect on reducing the increase in heat caused by traffic. City centres still remain too open to private vehicles despite the traffic problems they create. Also, swapping fossil fuel-based vehicles for electric vehicles will also play a role in reducing heat radiated, particularly with public transport!

Reducing Your Impact at Home

You may be reading this and live in the rural countryside so this probably doesn’t apply to you, but, given that the vast majority of people live in urban areas likely affected by the urban heat island effect I thought I’d write this anyway. Even just the smallest of actions can have an impact on the livability of your home and others living around you, so here’s a short list of a few things you can do to reduce the urban heat island effect in your area:

  • Plant trees, bushes, flowers or any other greenery
  • Shade large walls, patios or other surfaces that absorb heat
  • Replace darker roofs with lighter materials that reflect light and heat
  • Don’t pave your driveway – use gravel or another porous material that doesn’t absorb as much heat
  • Include a water feature in your garden

It may not sound like much or you may not think that doing any one of those things will have an impact in helping to cool our urban areas, but what I can promise is that it will make your house and your garden feel dramatically cooler. It may even encourage others to follow your example!




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