1This lecture addresses the urban heat island effect, whereby cities run several degrees warmer than surrounding countryside.
2The phenomenon was first documented in London during the nineteenth century, though systematic measurement came much later.
3Dark surfaces such as asphalt absorb solar radiation, while the loss of vegetation removes natural evaporative cooling.
4Initially, researchers blamed industrial emissions, but further analysis revealed surface materials as the dominant factor.
5What I want to emphasize here is that night time temperatures, not daytime peaks, pose the greatest health risk.
6During heatwaves, buildings release stored warmth after sunset, preventing residents from ever properly cooling down.
7Let me give you a concrete example: during one European heatwave, mortality rose sharply in districts lacking tree cover.
8Proposed remedies include reflective roofs, urban trees, and permeable pavements, each with distinct costs and limitations.
9White roofs were originally hailed as the cheapest fix, though their benefit diminishes considerably in colder climates.
10It was not the installation cost but the maintenance burden that deterred many councils from planting more trees.
11Moving on to outcomes, modelling suggests combined measures could lower peak city temperatures by several degrees.
12In conclusion, mitigating urban heat demands coordinated design rather than any single technological quick fix.