Climate change, thermal comfort, and energy efficiency: Meeting the challenges of cities in the 21st century

Scientific evidence for the warming of the climate system is unequivocal. Direct observations on and above Earth’s surface show the planet’s climate is significantly changing. Human activities are the primary driver of those changes. Cities are heating up; how can we keep them cool? The Urban Heat Island (UHI) is a phenomenon in which a metropolitan area has a higher temperature than the surrounding less developed rural areas. The concrete buildings, pavements, and other surfaces in cities absorb the midday heat and release it slowly into the atmosphere. In addition, air conditioners, cars, and other machines pump hot air into the street, making it near impossible for heat to escape. This effect increases the temperatures within cities, known as the urban heat island effect. Between 2000 and 2016, the number of people exposed to heat waves rose by a whopping 125 million, claiming more than 166,000 lives in the past three decades. This number will only increase with time, as the proportion of people living in urban areas is expected to increase to 70% by 2050. We must redesign our cities, including green roofs and rooftop gardens, and use reflecting surfaces. This paper discusses studies on thermal comfort (indoor and outdoor) and energy efficiency. The issues related to energy, climate and warming cities are highlighted, and recommendations are given for improving the environmental conditions.