Urban Heat Island studies in South Asia: A critical review

South Asian cities are home to nearly 15% of the world's urban population. These cities are experiencing rampant environmental deterioration, making them vulnerable to the impacts of climate change phenomenon, one of which is urban-rural temperature difference known as urban heat island (UHI) effect. While South Asian UHI research publications have tripled since 2000, a comprehensive overview of the experimental results, significant advancements and predominant directions in research is necessary to add clarity to the scientific understanding of tropical and subtropical urban climates and also, to aid city planning and policy-making. A review of 85 original research publications from peer-reviewed journals and conference proceedings in last five decades, covering 28 representative South Asian cities, revealed that Delhi, Chennai and Colombo were most frequently studied and satellite imagery based thermal mapping was used predominantly. Results from few significant studies have shown practical implications for energy use and management, human health, comfort and productivity, reducing air pollution and urban land-use planning. With similar patterns of urbanization, geographies and climate types prevailing across international borders, cities in South Asian region could mutually benefit from collaborative multi-disciplinary research efforts and knowledge sharing to competently respond to and manage the detrimental impacts of urban heat islands.