Cities in tropics may warm faster than surrounding areas under 2 degrees Celsius global warming: Study

New Delhi, Feb 4 (PTI) Tropical cities, including those in India, could warm faster than surrounding areas under 2 degrees Celsius of global warming, indicating potentially higher heat-related health risks for urban populations.

Researchers, led by those from the UK's University of East Anglia, produced projections for 104 medium-sized cities with populations ranging between 3,00,000 and one million.

Results published in the journal Proceedings of the National Academy of Sciences (PNAS) show the day-time land surface temperatures in 81 per cent of the cities are predicted to warm more than surrounding rural areas.

Co-author Manoj Joshi, from the Climatic Research Unit at the University of East Anglia, said, "Urban heat stress under climate change is an increasing concern, as many cities in the tropics and subtropics can be warmer than their rural surroundings, heightening their vulnerability to rising temperatures." The study combined "state-of-the-art" climate change projections with machine learning models to show how urban heat islands can be amplified in tropical and subtropical cities under climate change -- mostly in monsoon regions such as India, China and Western Africa.

"While global climate models are essential for projecting future temperature changes, they are limited in their ability to capture the trends of smaller cities. Even high-resolution global models can only predict changes for the largest urban areas or megacities," lead author Dr Sarah Berk, a PhD student at the University of East Anglia's school of environmental sciences, said.

"To bridge this gap, in our study we projected changes in land surface temperature in medium-sized cities, showing that in many of them, the urban warming rate is faster than rural surroundings," added Berk.

The cities studied are in the warmer parts of the world, which the authors said makes the increases even more significant for human health and the urban environment.

Medium-sized cities also represent a large proportion of global cities, with more than 2.5 times as many in this category than those with a population over one million, the team said.

"Under a 2 degrees Celsius global warming scenario, annual mean LST (land surface temperature) in 81 per cent of these cities is projected to increase faster than the surrounding area," the authors wrote.

"In 16 per cent of these cities, mostly in India and China, mean LST is projected to increase by an additional 50-112 per cent above ESM (Earth system models) projections of the surrounding area," they said. PTI KRS (please also select TAR Before running the story) KRS KRS