such as "Introduction", "Conclusion"..etc
May 2007 -- Scientists looking at the effect global warming will have on our major
cities say a modest increase in the number of urban parks and street
trees could offset decades of predicted temperature rises.
The University of Manchester study has calculated 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°C.
This 4°C drop in temperature, which is equivalent to the average
predicted rise through global warming by the 2080s, is caused by the
cooling effect of water as it evaporates into the air from leaves and
vegetation through a process called transpiration.
"Green space collects and retains water much better than the built
environment," explained Dr Roland Ennos, a biomechanics expert in
Manchester's Faculty of Life Sciences and a lead researcher in the team.
"As this water evaporates from the leaves of plants and trees it
cools the surrounding air in a similar way to the cooling effect of
perspiration as it evaporates from our skin."
Taking Greater Manchester as their model, the team used Geographic
Information System (GIS) mapping to build up a picture of the
conurbation's land use. The team then worked out the impact that
increasing the amount of green space would have on the urban climate as
well as on water retention.
"Urban areas can be up to 12°C warmer than more rural surroundings
due to the heat given off by buildings, roads and traffic, as well as
reduced evaporative cooling, in what is commonly referred to as an
'urban heat island'," said Dr Ennos, who worked on the project with
Professor John Handley and Dr Susannah Gill in the School of
Environment and Development.
"We discovered that a modest increase of 10% green space reduced
surface temperatures in the urban environment by 4°C, which would
overcome temperature rises caused by global warming over the next 75
years, effectively 'climate proofing' our cities.
"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
The research, published in Built Environment, also examined the
effect increased green space would have on the amount of rainwater
urban areas capture and retain; towns and cities lose a large
proportion of rainwater through what is termed 'run-off' where
precipitation quickly leaves the surface and drains away into streams
and rivers, eventually returning to the sea.
"By the 2080s, our summers will be hotter and drier but winters are
predicted to become wetter," said Dr Ennos. "An extreme wet winter's
day by the 2080s will deliver almost 50% more rain than is currently
"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
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