This so-called “urban heat island” effect can\u00a0push temperatures up by 10 to 15 degrees Celsius<\/a> (18 to 27 degrees Fahrenheit), making residents<\/a>\u00a0vulnerable amid\u00a0extremely\u00a0hot conditions<\/a>.<\/p>\n What causes urban heat islands?<\/p>\n Rural areas are usually covered in grass, crops or forests which helps cool the air, whereas the city’s dark concrete and asphalt absorb heat<\/a>.\u00a0<\/p>\n Plants work as nature’s air conditioner<\/a>\u00a0,\u00a0taking\u00a0water from the ground through their roots and then releasing it as vapor into the air. Impervious hard, dark surfaces such as sidewalks, parking lots and roads don’t allow water to trickle in and therefore do not\u00a0provide this cooling effect.<\/p>\n Tall buildings and narrow streets can heat up air that gets trapped between them. These “urban canyons” can block the natural flow of wind<\/a> that would otherwise help cool the area down.\u00a0<\/p>\n Pollution from cars or the burning of fossil fuels can act as a miniature greenhouse layer over a city, keeping hot air trapped.\u00a0<\/p>\n Heat islands often build throughout the day as sidewalks and roofs emit more of the sun’s heat \u2014 peaking at around three to five hours after sunset.<\/a>\u00a0<\/p>\n From sunrise until late afternoon, these surfaces are exposed to intense solar radiation and absorb heat through numerous layers. This stored heat is then slowly released after the sun has gone down.\u00a0<\/p>\n Where is the urban heat island effect hitting hardest?<\/p>\n Bigger cities tend to store more heat than smaller ones. The urban centers of London<\/a> and Paris are often\u00a0around 4 degrees Celsius warmer\u00a0than rural surroundings at night.\u00a0<\/p>\n The heat island effect is compounded by the rise in overall global temperatures.<\/p>\n 2024 was the hottest year on record at about 1.55 degrees Celsius<\/a> (2.79 degrees Fahrenheit) above pre-industrial levels. Current policies are projected to see that rise continue\u00a0to 2.7 degrees Celsius<\/a>by the end of the century. This is caused by burning planet-heating fossil fuels that release greenhouse gas emissions into the atmosphere.<\/p>\n In turn, such heat islands could also be fueling climate change<\/a> as the demand for air conditioning powered by the burning of coal, oil and gas rises during heatwaves.\u00a0<\/p>\n Are there solutions to cool down cities?<\/p>\n Yes \u2014 solutions<\/a> include greening cities by adding more drought-resistant trees, shrubs and other green vegetation to urban centers, as well as fountains and ponds, green or “cool roofs”<\/a> that absorb and transfer less heat from the sun to the building.<\/p>\n Such cool roofs reflect more sunlight than a conventional surface and therefore don’t heat up as much. White roofs stay coolest and can reflect about 60 \u2013 90% of sunlight, but other reflective surfaces are also an option.\u00a0<\/p>\n Cities such as New York<\/a> started painting roofs white<\/a> in 2009 to help curb the heat island effect. Cooler rooftops can also reduce internal building temperatures by up to 30% and lower air pollution and greenhouse gas emissions by reducing demand for power to cool the building.\u00a0<\/p>\n At ground level, some countries\u00a0spray\u00a0water on sidewalks for cooling. In Japan<\/a>, it’s a centuries-old traditional practice in Japan called “uchimizu.”<\/a>\u00a0<\/p>\n Others are\u00a0mixing residential, commercial, and recreational spaces or installing “cool pavements”<\/a> that use permeable materials to reflect more of the sun’s radiation and enhance water evaporation.<\/p>\n Megacities like Los Angeles and Tokyo have laid such cool pavements.\u00a0A study in one of Los Angeles’ hottest neighborhoods<\/a> found that reflective pavement coating could reduce the heat island effect.\u00a0\u00a0<\/p>\n The city government of Tokyo has rolled out around 200 kilometers (about 124 miles) of such sidewalks so far, prioritizing areas in the city center. By 2030, Tokyo aims to cover 245 kilometers of metropolitan roads.\u00a0<\/p>\n Singapore: Fighting heat with greenery Lighter colored paving leads to less heat being absorbed and then releasedImage: City of Phoenix via AP\/picture alliance<\/p>\n