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Research – Green zones reduce effects of global warming in cities

Posted in Research by fedwards on May 30th, 2007

LeavesGreen Roof

Need more research to support increased green space in cities? A study recently released by the University of Manchester states that “a mere 10% increase in the amount of green space in built-up centres would reduce urban surface temperatures by as much as 4 degrees. The reduction in heat occurs due to a process called transpiration, when water evaporates from leaves and vegetation cooling the surrounding air. Dr Ennos, who worked on the project with Professor John Handley and Dr Susannah Gill states:

“Such a reduction has important implications for human comfort and health within urban areas and opportunities need to be taken to increase green space cover wherever structural changes are occurring within urban areas, as well as planting street trees or developing green roofs”.


Increased green space also has implications for water storage in the city.
According to Dr Ennos:

“By the 2080s, our summers will be hotter and drier but winters are predicted to become wetter. An extreme wet winter’s day by the 2080s will deliver almost 50% more rain than is currently experienced. Based on an existing model, we have calculated that these more powerful storms would increase the amount of run-off from urban areas by more than 80%. Unfortunately, increasing the amount of green space only has a limited effect in reducing run-off and so flash flooding will become an increasing problem in our cities. Conversely, the warmer, drier summer months will reduce the amount of water available to plants and, during the longer droughts, this will reduce transpiration with its associated cooling effect. In order for the cooling effect of green spaces to work when it is most needed, cities would need to develop ways to store additional water, which could then be used to irrigate the green spaces during drier months.”

See the University of Manchester website for more information. The research report has also been published in Built Environment.

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