It has been known for a long time that the city is warmer than the countryside. This heat island effect can reach more than 7 degrees Celsius and can pose a serious problem for the elderly and young children. The effect is due to heat emissions from buildings and cars and from buildings that retain heat. The solution is simple, green reduces the temperature difference. You must especially ensure that you drink enough and that young children and the elderly do not overheat or dehydrate.
Research
In the early 19th century, London chemist Luke Howard made the first observations about the city’s temperature. He found that densely built-up areas in London were warmer than the countryside. Since then, much more research has been done into temperature differences between city and countryside, the causes, the consequences and how to limit them.
What is it exactly
The difference in temperature between the city and the countryside is called the heat island effect. The city is, as it were, an island of warmth in a sea of coolness. The existence of the effect has been known since the 19th century, but only recently has much research been done into it. The effects are increasing, especially now that they are combined with strong global population growth and climate change.
How much difference does it make?
In cities it is on average 2.4 degrees Celsius warmer than in the countryside. This is the average over the entire year, day and night. During clear, windless nights the differences are greatest and can amount to 7 degrees for a city with 200,000 inhabitants. It is the warmest in the city center, in the suburbs the temperature is already dropping. The density with which people live together is also important. The more people live in a small area, the warmer it becomes. In this way, the temperature difference of 7 degrees, which occurs in the Netherlands, can be even greater in cities full of skyscrapers in America, for example. In the Netherlands, Rotterdam is the city with the biggest problems with heat stress. It is on average 2.8 degrees warmer here than outside the city.
How come?
The difference in temperature can be quite significant, but why is this? There are two factors that play a role. First there is heat production, which is greater in the city than in the countryside. Secondly, cities retain more heat than rural areas.
Heat production
Heat is produced all around us. People and animals produce heat, but this is only small amounts. In winter, houses are heated, which produces large amounts of heat. Air conditioning and ventilation in houses in the summer does not reduce the temperature, energy is supplied that is ultimately converted into heat. All year round, cars and air pollution cause an increase in temperatures.
Retain heat
A second factor that causes the increase in heat is the dense buildings. As a result, a gust of wind can no longer provide cooling, the heat is not dissipated. The heat is retained, so the temperature only continues to rise.
The consequences
A few degrees warmer, for many people it doesn’t really seem to be a problem. Yet it causes major problems. In summer the temperature difference can be up to 5 degrees Celsius, even in the Netherlands and Belgium with a relatively mild climate. For older people and young children, such a temperature difference can be a serious problem. This heat stress, as the high temperature is called, therefore causes major problems. There are already indications that there are more deaths on hot days than on cool days.
Limit effects
The effects of the city can easily be limited by planting more greenery. For every percent more green cover, the effect decreases by 0.06 degrees. This may not seem like much, but it is an average. Green has more benefits than just limiting the heat, it has positive effects on people’s behavior and health. A less dense road network and building less densely together would also be a solution. However, with a growing population and more and more cars, this is unlikely to happen.
What can I do myself?
There are also things you can do yourself to combat the heat. You can contribute to limiting the heat by generating less heat emissions, but you can also provide cooling for yourself.
Reduce heat emissions
You can reduce heat emissions yourself by using the car less and turning down the heating. Furthermore, there is little you can do yourself to lower the temperature, but you can respond to it.
Looking for cooling off
On hot days it is important to drink enough. Make sure that young children and the elderly get enough water. Cooling down is also especially essential for young children and the elderly. A fan can provide the solution, but a day out in the countryside, the forest or going swimming is also a solution. The temperature in the house can be properly regulated by keeping the windows closed during the day and opening them at night.