Urban Heat Islands An urban heat island is a metropolitan area which is significantly warmer than its surrounding rural areas.

Bare earth and vegetation

Water

Albedo

Buildings and the Ground Store Heat

Sources of Heat

Cityscapes v landscapes

Energy in and out

London, 2000 British Museum Richmond Park

London, Summer 2000 Sunrise sunset

Chicago

The urban heat island is biggest… At night (before sunrise) In the summer When there is no wind When the sky is clear When the weather doesn’t change through the night

Excess mortality rates in early August 2003 indicate about 40,000 heat-related deaths Daily mortality in Baden-Württemberg

observations HadCM3 Medium-High s Temperature anomaly (wrt ) °C European 2003 summer temperatures “Right now, we average about 14 days each summer above 90 degrees in New York. In a couple of decades, we could be experiencing 30 days or more,”

What’s that got to do with the UHI? London – 600 heat related deaths in August 2003 Up to 9 °C warmer than surrounding rural areas Mortality increases with temperature when temperatures are over 22°C Mortality particularly linked to warm night time temperatures Mortality linked to age, sex, deprivation etc. Challenge now to design buildings and urban areas for the future – which will see more people living in cities, and will be warmer.

Other Consequences The growing season can be up to 15 days longer in a city! Warmer in a city in winter Rainfall

How to reduce urban heat islands