Portsmouth, home to 208,000 people on England's south coast, has been identified as Great Britain's most vulnerable city to extreme heat, according to a new heat vulnerability index created by Ordnance Survey (OS), the Met Office, and 4 Earth Intelligence. The research indicates that Portsmouth will remain at the highest level of warming until the end of the century.
The analysis suggests that Leicester is projected to experience the most significant increase in heat vulnerability, rising from 10th to fourth by the end of the century. Exeter and Nottingham are also expected to enter the top 10 most vulnerable cities, alongside Bristol and Brighton and Hove, by the close of this century.
The OS heat vulnerability index, which analysed 71 cities across England, Scotland, and Wales, predicts that all 71 cities will reach high heat vulnerability by 2040. By the turn of the century, almost two-thirds of these cities could reach the most severe level of vulnerability.
Cities are particularly susceptible to extreme heat due to concrete, asphalt, buildings, and hard surfaces absorbing solar radiation and retaining heat, a phenomenon known as urban heat islands. Areas with less tree cover, green space, and waterways are most at risk of extreme warming.