Warangal’s urban heat index doubled in two decades, finds study | Hyderabad News

Hyderabad: Warangal appears to be following Hyderabad’s heat trajectory as urbanisation and industrial activity expand, with a new study finding that the city’s urban heat intensity doubled between 2003 and 2023.The finding comes from a study titled “Data-driven assessment of industrial influences on urban heat index dynamics across Telangana, India”, published in Scientific Reports academic journal. The researchers analysed satellite data, land-use changes and meteorological variables across Telangana over two decades, with a separate case analysis of Warangal as a secondary industrial city.

Warangal’s mean Urban Heat Index increased from 1.2 in 2003 to 2.4 in 2023, doubling over the period. The area identified as a statistically significant heat hotspot also expanded by about 62%. Researchers found that expansion of the industrial corridor towards the north-eastern part of Warangal coincided with the spread of high-heat zones.The Urban Heat Index is a measure of the difference in surface heat between an urban area and its surroundings. It is not the same as the air temperature recorded by weather stations. In simple terms, the higher the index, the stronger the urban heat island effect.Warangal findings have a striking parallel in Hyderabad. The Centre for Science and Environment’s Urban Heat Stress Tracker Hyderabad, published in 2024, found that Hyderabad’s built-up area more than doubled between 2003 and 2023. Built-up land increased from 298.3 sq km, or 20.6% of the city’s geographical area, in 2003 to 636.58 sq km, or 44%, in 2023.The CSE report also found that Hyderabad’s heat behaves differently during the day and night. During summer daytime, the city’s core was 0.7°C cooler than the surrounding peri-urban areas. At night, however, the core was 1.9°C warmer, indicating that built-up areas retain heat after sunset. The report also found that the difference between daytime and nighttime land-surface temperatures had declined by 13%, indicating weaker nighttime cooling.The two studies cannot be used to say that Warangal is as hot as Hyderabad because they use different indicators and analytical approaches. But their findings point to a common pattern: as cities expand and open land is replaced by built-up surfaces, their thermal environment changes.The Telangana study provides stronger evidence of the industrial component of this change. Across the state, the mean Urban Heat Index in industrial areas increased from 1.35 in 2003 to 2.70 in 2023. In non-industrial areas, it rose from 1.00 to 1.82. Industrial zones also recorded higher land-surface temperatures throughout the study period.Warangal is significant in this context because the city is not on the scale of Hyderabad, yet it recorded a doubling of its urban heat intensity over the same 20-year period. The researchers identified industrial land use, built-up density and near-surface air temperature as the dominant factors associated with changes in the Urban Heat Index, while vegetation was found to have a moderating effect.The findings do not establish that industrialisation alone caused Warangal’s rising heat. Urban expansion, changes in land cover and background warming also contribute. But the spatial overlap between the expanding industrial corridor and growing heat hotspots suggests that industrial land use is an important part of the city’s changing thermal landscape.