Climate Change Intensifies Heat Island Effect in the Tropics

Researchers use machine learning to uncover accelerated warming in tropical cities and establish a basis for adaptation measures
World map highlighting urban heat island increases (red) and decreases (blue) points across continents, with a legend on the right. Sarah Berk
Urban heat island effect in cities worldwide – surface temperatures are rising particularly sharply in India, China, and West Africa.

Cities are often warmer than their rural surroundings. This urban heat island effect is often particularly pronounced during heat waves. Therefore, it is a key question is to what extent climate change could further increase the discrepancy between urban and rural areas. This could lead to considerable health risks, especially in warmer regions, which is why reliable projections are essential, particularly for tropical cities. Researchers at Karlsruhe Institute of Technology (KIT) and the University of East Anglia in England have now examined 104 medium-sized cities in the tropics and subtropics with respect to their projected temperature changes.

Machine Learning Addresses a Central Modeling Gap

"Common global climate models reach their limits in terms of resolution when representing trends in smaller cities. High-resolution urban models, in turn, cannot be applied on a large scale," explains Tenure-Track Professor Peer Nowack from the Institute of Theoretical Informatics at KIT, who co-supervised the study. Nowack and his research team therefore use machine learning to translate global, low-resolution climate projections into local changes in urban heat islands.

The researchers found that around 80 percent of the 104 cities investigated in India, China, and West Africa exhibit a significantly faster rise in temperature than their surroundings. In about 15 percent of cases, urban warming may be 50 to 100 percent higher than would be expected with an average global warming of two degrees Celsius. The international research team was thus able to show for the first time that medium-sized cities – where a large share of the world's population lives – could be exposed to previously underestimated heat stress in the future. The findings can help to better assess health risks and to develop targeted urban heat adaptation measures in the affected areas.

lla, February 12, 2026