The heat wave continues…. and what we should be doing about it

Wow! It’s still brutally warm, it’s now 4.52am, and I can’t sleep.

The heat may not seem like an issue, but several nights over 25 degrees and vulnerable members of society may be at risk.

The article below describes what we can do to reduce heat-related health problems in our communities and how to make Cardiff a more comfortable and healthier place to be during the summer.

Arguably the worst 'public realm' space in Cardiff. Nine widely-spaced half dead trees in a large paved triangle. One bench. Time to invest in a landscape architect, Cardiff?

Arguably the worst ‘public realm’ space in Cardiff. Nine widely-spaced half dead trees in a large paved triangle. One bench.

Heat waves are particularly damaging in towns and cities, where the daily high temperatures get absorbed by the concrete, asphalt and brick, and stored there. If you don’t believe this, try walking down City Road and Albany Road to the park. The few trees that have been planted along the streets cast almost no shade due to their meagre size. As the night time air temperature falls, the heat is released from the buildings and roads, keeping the city much warmer than the surrounding countryside. The nights are hot and uncomfortable. If you can’t sleep because of the heat, open windows feel like they should help, but now you are just hot and kept awake by the seagulls as well. For me, this is annoying, but this can be a particular problem for hospitals and nursing homes. Getting good quality sleep is extremely important for recovery from illness and most hospitals are not set up with air conditioning.

The longer a heat wave lasts, the more damage it can do. With sunshine and lack of wind also comes pollution, particularly ozone. (Ozone is good at high altitude, but when it forms at ground level, it can be very bad for human health.) Very small particulates are also formed by engines, and with a lack of wind to disperse these particles, they just float around close to the roads, leading to respiratory problems for those who live and work nearby. (For our local air quality, see the Welsh Air Quality website.)


A riverside walk in deep, cooling shade in Bute Park

Heat waves are only a problem for the vulnerable people in the city. Following the Chicago heat wave of 2003, a research team reviewed the deaths that had occurred. In densely settled neighbourhoods with busy streets and public spaces, such as the Little Village, the people fared much better than areas where people were more disconnected from neighbours and had few places to gather, such as North Lawndale. The deaths are therefore a fault of society not caring or noticing its vulnerable members. Heat waves kill the invisible people in our community. Therefore no-one notices apart from the funeral home owners.

There are things that we can do about this:

    1. Look out for your neighbours. Offer to walk with them to your nearest shady park, take an umbrella to shade them from the sun during the walk, and plenty of liquids. The temperature under large trees can be 10 degrees cooler than in the open.

    2. Try not to drive. The pollutants are so much worse during hot weather, and you will be impacting children with asthma as well as older people with lung issues.

    3. Consider planting trees in your garden if possible, as the shade they create cools the air around, and reduces the urban heat island effect. Trees at the front of your house have the added benefit of shading near the road, where dangerous ozone can be formed when the combustion of diesel occurs in strong sunlight. The next best thing is a hedge. Aim for anything that will shade the hard manmade surfaces that absorb so much heat. Ideally the trees should be supplied with water from the roof to avoid them drying out. Planting climbing plants for house and garden walls, like Mark has done, can reduce the amount of heat that is absorbed. There is also evidence that plants with silvery, furry leaves can cool the air around them more than green leaves.Lambs ears

    4. Campaign for more large street trees in Cardiff, as these are our best defence against the harmful effects of heat waves. They create shade like an umbrella, so even at mid day, the ground is still shaded. The air that passes through this area also cools down, and nearby buildings benefit from reduced energy usage for cooling buildings. Tall trees also shade the windows during summer, and allow light through in winter, exactly when we need it most. Trees that shade our busiest traffic routes will reduce pollution levels that become worse during hot summers.

The Hayes, Cardiff. The large street trees provide welcome shade in the town centre.

The Hayes, Cardiff. The large street trees provide welcome shade in the town centre.

Many of the large trees that we appreciate were planted during the Victorian era, and many are now reaching the end of their lives. Many councils are replacing larger trees with smaller amenity trees. These are not trees to walk or drive under, but they protect the council from worries about large root system, plus they reduce the leaf clearance required in autumn. The development of root barriers and much better appreciation of the requirements to maintain trees means that large trees planted now would not cause foreseeable issues. We need to encourage our council to be braver with their tree planting choices where there is space to allow a full sized tree.


The council have done a great job of using street trees in the newly developed outdoor space

A great summary of urban heat island development is given by the EPA.

Cardiff’s urban heat island is discussed in the paper here.

These are just some thoughts about how we should be looking to reduce the impact of high temperatures, but please feel free to comment with some further ideas.


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