Portsmouth tops heat vulnerability index for cities

Ordnance Survey has published a Heat Vulnerability Index ranking all 71 cities in Great Britain by their exposure to retained urban heat.

The index finds that 59 of the 71 cities, or 83%, already fall into the high heat vulnerability category.

Urban heat islands form when buildings, roads and other hard surfaces absorb heat during the day and release it slowly overnight.

External research cited in the analysis points to the health and economic cost of urban heat in the capital.

Even so, it is still projected to move from moderate to high heat vulnerability by 2040 and remain there through the end of the century.