11/16/2017 0 Comments URBAN HEAT ISLAND EFFECT: THE PHENOMENON CAUSING NAIROBI TO HEAT UP TO DANGEROUS LEVELSTemperatures are currently rising to dangerous new highs in Nairobi, Kenya, due to the urban heat island (UHI) effect. Effects of the heat are already being felt, with many people complaining of heat exhaustion, lethargy, extreme thirst, and inability to fall asleep. With public transport options being limited to the chaotic and unruly matatu sector, the city is starting to feel even more uninhabitable than usual as residents are forced to walk long distances, except this time around it's in the ever-rising temperatures which makes them susceptible to heat-related health emergencies. To add insult to injury, infrastructure projects by the government are dedicated to cars and those who own cars, creating a vicious cycle that not only reinforces poverty but also increases the heat in the city. Therefore, today's post is dedicated to disseminating information about UHI. What is UHIUHI is a phenomenon whereby a city/town is significantly warmer than the surrounding areas. Like many other weather/climate-related occurrences, it is caused by human activities such as land modifications including buildings and roads which trap heat in the city/town, consequently raising the temperature. UHI is dangerous to humans and other living organisms as it makes living conditions unbearable, and cities/towns that become too hot can end up being unable to sustain life. Causes of UHIUHI can be traced back to the geography of a place being disrupted by materials that heat up faster and absorb more heat. For example, dark surfaces are good absorbers of heat (they absorb heat very quickly) and good emitters of heat (they release heat very quickly). Light surfaces on the other hand tend to reflect heat more than they absorb it, hence are bad absorbers of heat. Light surfaces are also bad emitters of heat. Basically, good absorbers are good emitters. What this means, in the context of UHI, is that pavements, roofs, and roads, commonly made of asphalt and concrete which are dark surfaces, absorb a lot of heat during the day when it is sunny. This is why in some cities, especially reported in Australia, people are warned of wearing plastic shoes during the summer as the plastic melts while they are walking on the roads and pavements and their feet are badly burned. These surfaces emit heat during the night. On the other hand, light and reflective surfaces, such as the ones used in buildings, tend to reflect the heat. Because urban areas have many buildings, there are multiple surfaces for the heat to be reflected on and so the heat 'bounces' off from surface to surface. Additionally, vehicles also emit a lot of heat, and urban areas tend to be packed with traffic. And, because there isn't that much vegetation in cities, the cooling effect of trees is not present. Carbon dioxide clearance from the air is also poor as this is another function of vegetation. To make things worse, people in hot cities tend to cool themselves with air conditioning units, but this actually ends up making the city hotter as the aircon units funnel the heat outside thus continuing the UHI heat loop. And the hotter it becomes, the more aircon units are used. The more aircon units are used, the hotter it becomes. UHI in KenyaScientists studying UHI in Kenya have found that it affects the cities of Nairobi, Kisumu, and Mombasa as well as the urban area of Thika. The situation is far worse in Nairobi as the city has been given a make-over to "reflect its status as the country's capital". Nairobi has changed drastically throughout the years, so much so that parts of it now look more like New York or LA than they do Nairobi. And this comparison isn't by accident: many of our policies are taken from the worst of what America has to offer. We have taken the bad housing policies, the bad education policies, the bad traffic policies, the bad energy policies...all of it. And while many may be fooled by the "Africa rising" facade that is the picture of Nairobi above, that is Nairobi on its death bed; a Nairobi governed by massive wealth inequality and under a dome of heat, literally and figuratively. It's a ticking time bomb. Between 1988 and 2016, Nairobi lost 22% of its vegetation cover. Aside from cooling the city, the vegetation cover also improves local biodiversity and stormwater retention. Temperatures in the city increased from an average of 18.8°C in the 1950s to 19.5°C in the 2000s (pdf) to the mid-twenty degrees in the 2010s. A study by Silas Owiti (pdf) successfully showed that not only is Nairobi experiencing UHI, but that there are various heat islands concentrated in various areas in the county, and that these heat islands consistently experience 0.5-3.5°C above the average temperatures of the surrounding areas regardless of the season, warm or cold. Nairobi also has several micro-climates, with UHI being exhibited in some of those micro-climates e.g. in Kibera. The presence of the micro-climates is due to Nairobi having heterogeneous surfaces i.e. different types of surfaces existing together, e.g paved roads, high rise buildings and low vegetation in the central business district, and metal housing, unpaved roads, and little vegetation in informal settlements otherwise known as slums. People living in informal settlements are especially vulnerable as they are cut off from many social services such as water, sanitation services, hospitals, emergency services, and many other services that are citizen-funded but government-provided. This is alarming as high temperatures lead to a number of health problems as elaborated below. Effects of UHIThe increased temperatures affect the living things in the area. Plants experience stunted growth and/or wilt and animals and people suffer from hyperthermia. There has been an increased reporting of heat shock, heat exhaustion, and sunburns in the cities and most people affected do not have access to sunscreens hence raising the risk for skin cancer. People also experience heatstroke, a life-threatening condition that can lead to permanent organ damage. High temperatures in water bodies lead to a decrease in biodiversity in said water bodies. Solutions to UHIFor the government:
1. Developing public transport infrastructure. Trains (rail, subway, trams) and buses are the answer to solving the traffic problem; building more highways and adding more private cars is like pouring kerosene in the fire. 2. Green architecture and urban planning i.e. stop cutting trees for your construction projects, plant more trees, create more green spaces, build eco-buildings, plan for people not for cars and corporations. 3. Curb air pollution. 4. Cease expansionist projects and focus on projects that mitigate and combat the effects of the climate crisis. For the people: 1. Demand accountability from the government. 2. Learn about the role that corporations and donors play in the destruction of our environment and how we can stop them.
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