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Rising global urban temperatures have already reached dangerous levels. The heatwave in North America from June to July was literally killing heat. The results of a survey on exposure to heat in 13,115 cities around the world from 1983 to 2016 were published in the Proceedings of the National Academy of Sciences of the United States of America.
There are two main reasons for the increase in temperature in cities. First, the global population is concentrated in urban areas. Next, it is due to the fact that the city temperature is rising every year due to the effect of global warming.
In the study, to investigate how hot and humid the city is, the temperature was investigated using a dataset that combines infrared satellite images and measurements from the Korea Meteorological Administration. This made it possible to conduct a wide range of investigations, including areas with sparse ground sensors.
In this study, the sweltering state was defined as a wet-bulb temperature of 30 degrees or higher, and the frequency of occurrence of this temperature was paid attention to. When the wet-bulb temperature is above 30°C, the sensible temperature is above 41°C. It is difficult for even healthy people to work outdoors for a long time at this temperature, and the elderly or people with underlying diseases may even pose a risk to their lives. For reference, wet-bulb temperature is to determine what kind of condition the human body can respond to in a complex index that combines temperature, humidity, thermal radiation, and wind measurement values.
It also used city demographics and weather data over 33 years to determine how much of the population was exposed to heatwaves.
The number of years city dwellers were exposed to extreme heat was 40 billion per year in 1983, but tripled to 119 billion in 2016. Two-thirds is due to population growth and one-third is due to global warming, but the proportions vary widely from city to city.
Among the cities surveyed, Dhaka, Bangladesh, with the highest frequency of exposure to dangerous heat, increased by 575 million over 33 years. As the population of Dhaka is rapidly increasing, the population of Dhaka, from 4 million in 1983, is now 22 million.
The rise in temperature has also had a major impact on other major cities such as Baghdad, Cairo and Mumbai. The same is true for European cities, where the number of people suffering from heat stroke is increasing due to rising temperatures and population growth is flat in Gulf coastal cities.
There are several factors contributing to urban warming. The first is the urban heat island phenomenon. The increase in temperature in urban areas is due to the materials used for roads and buildings. There are also historical factors. Most of the ancient civilizations were born in hot and humid river areas such as the Nile, Niger, Ganges, and Indus. It was the perfect place to engage in agriculture or develop a city. However, it was also an area that produced scorching heat due to heat and moisture. It is also an area with a rapidly growing population. In most of the studies, population growth is a major factor in the increased risk of heat island in regions that are already warming.
The research team said that this study shows how much it is necessary to take measures now to protect city dwellers amid an increase in urban temperature and population. It says it is necessary to take measures to do this. It’s also important for city dwellers to understand the risks of heatwaves, to make it easy to get to places with fans or air conditioning, and to ensure that residents have access to air conditioning in their homes during a heat wave even if they pay their bills arrears.
Research on alternative cooling means such as air conditioners that do not emit harmful greenhouse gases, reviews for introducing efficient heat pumps into homes, and low-cost cooling costs are also being reviewed, but efforts are needed to reduce the risk of life due to heat waves. Related information can be found here.
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