CIC Start Online Conference 2011 - Glasgow Caledonian University

Hello welcome to our presentation on an urban heat island study here in Glasgow
This work looks at the urban heat island phenomenon here in Glasgow and explores the linkages
to global climate change adaption and resilience debate.
The work is being done by the sustainable urban environment group at the Glasgow Caledonian
University School of Built and Natural Environment, in collaboration with Prof Eduardo Kruger
who is a visiting research from the technological university of Piranha in Brazil.
This presentation is on the Urban heat island effect and it’s linkages to global change-
we want to look at the management an adaption of local climate change as a strategy for
enhancing the resilience and sustainability of cities to global climate change.
The presentation is in three parts The first part looks at the background to
urban warming and its linkages to global climate change.
We explore the urban heat island phenomenon itself and the wide implications for the adaptation
and mitigation debate surrounding global climate change.
We then look at our own research work at Urban Heat Island here in Glasgow, the objectives
of the work, the protocols – it’s an ongoing study so we present some early key findings
and implications. Finally the presentation also looks at the
wider objective of adapting cities and the resilience related questions and present some
findings on the way forward The urban warming and it’s linkages to global
climate change The world is now largely urban. The United
Nations estimated that in 2010, more than 50% of humanity began to live in cities. Which
is very new in terms of human civilizational history. There is no precedent for such large
movement to cities. Much of this growth is in the warm world – 7 of the 10 fastest
growing cities are in the warm, humid tropic cities such as Dakar, Manila, and so forth.
Yet for all this growth – cities occupy less than than 3% of global surface area.
Even with half of us living in the cities, the cities relatively are a small area covered
by urban growth. As such they cannot directly influence the global climate change.
Yet cities warm faster than rural areas. This is especially the case in the growing part
of the world here are some examples from south and south-east Asia. As can be seen in these
images, throughout the seasons, throughout the year, urban areas warm much faster than
their rural counterparts. So even though the cities occupy a tiny fraction of global surface
area, their effect, indirect effect can be quite dramatic.
How do cities change the climate? Here is an image of the incoming solar radiation
and it’s partitioning. Approximately 340 W/m2 of energy is received from the sun by
the Earth. One third of it is immediately reflected back. However two thirds of it is
available for heating the atmosphere and the surroundings immediately above the earth’s
surface – this is what the city has influence over.
Here is an image that shows how the city interferes with the energetic of solar radiation. A City
is an efficient “trapper” of solar radiation. You can see here that the city causes limited
sky view which limits the amount of sky dome that is available for the city to lose heat
to, the city also has multiple surfaces which cause multiple reflections which in effect
causes an increase in incoming radiation. There are more man-made surfaces in cities;
they are an efficient trapper of heat. Additionally there is pollution and human activities that
generate their own heat, so all of this interferes with the energy formation and flow through
the city, and that leads to the urban heat island effect.
There are also flow related effects that’s the horizontal convection of wind and energy
flowing across the cities. This image indicates a schematic of how the city influences the
flow, the incoming air is efficiently trapped and trained; the surfaces are rough which
causes the flow to be much more turbulent – this together with dust and heat and pollution
generated by the city causes effects not only on the city but also down-stream where there
is good evidence now of the city’s effect on for example thunderstorms, rainfall, etc,
outside the city’s limits. So there is not only an energy effect but also a flow, a convection
related effect caused by the city. So even if the city itself occupies much less land,
the footprint, the climatic footprint could be much larger.
All of these effects have wide implications, not only on the city but also regional and
global climate change. At least three could be seen in recent literature. The warm air,
as I indicated on the previous slide, and the air plume, generated by cities, then can
also alter the atmospheric chemistry itself, the efficiency of the atmosphere in trapping
that heat, so even if the city itself occupies less land area, the city could in theory alter
the chemistry of the atmosphere over large areas and could influence regional and perhaps
even global climate. All of this is happening when the city areas
are less than the 3% and the population is only 50% of the total global population. The
UN estimates that in the next 30 years, 75-80% of us will be living in cities which will
obviously mean there will be an increase in urban land area and the effect could therefore
be wider. So that would be another wide implication. Thirdly, cities have a change on the land
use effect as well. Cities generated land cover and land use changes have wider implications.
Recent studies estimate up to a third of a degree change per century could have come
from cities and associated agriculture. That’s about 15-33% of the recorded climate change
and therefore it could be; going forward it could be similar. SO a third of the effect
could be directly due to cities growing rapidly though the land use changes.
It is in this context that our work on Heat Island here in Glasgow is being presented.
The objectives of this study is to look at the influence of city forms urban morphology
in terms of building density, trees, water bodies, etc. on the local climate change here
in Glasgow. We want to also explore the linkages between such local change and the regional
and global change and how these could affect the adaptation possibilities of the city.
And finally, what are the sustainability dimensions of urban planning to mitigate urban heat island
effect. We use four strands of research methodology
here to study the heat island effect here in Glasgow, firstly we look at the historic
trend over the last 60 years, how climate in and around the city has changed. We used
historic data for this. We then look at the local intra-urban variation
by setting up weather stations in and around the city.
We also study the minute variation of micro-climate at street level within the the city core area.
And finally, how people are adapting to the urban warming and that might tell us something
about what the future holds in terms of resilience to climate change in the city.
For the purpose of historic trends in local climate, we analysed the last 60 years of
data of weather stations in and around the city of Glasgow. Here we present the data
from 4 stations around the city. And all of these have data going back at least
to the 1950s which enables us to look at both the regional climate change and the local
variations caused by the city. Given the fact that the city climate change
is caused by land use and land cover changes, we used a climatic classification recently
developed for cities by Stewart and Oke. The city is caused lCZ, local climate zone.
The local climate zone is an amalgamation of land cover, land use, building density,
building height, green cover, etc. And local heat generation which generally classifies
urban land use into 16 categories. Here we present four of them in and around the city
of Glasgow. Each of the stations have slightly different
variations, since Glasgow is a fairly low density city we wouldn’t find high density
land use here, but most of them are variations of low-rise and open-set land cover. The historic
trends in local climate around Glasgow indicate there is definitely a warming trend, especially
in winter time in the city. The number of days where the urban rural temperature difference
is more than 2 degrees is 30-65% in the city. Indicating that the city has a clear warming
trend inside it. And the annual variation is, while smaller,
as I said before the effect is clearly more pronounced in winter time – which unlike
in many urban heat island effects found around the world could be a positive thing that could
be used by the city of Glasgow in its quest for climate resilience and climate change
adaptation. So Glasgow is definitely warmer than its surroundings
and the effect is more pronounced in the winter which has energy and carbon implications unlike
in many cities around the world, here it is a problem that is positive in terms of its
effect on energy use and carbon management. The warming effect is more pronounced in built-up
areas, so there are variations within this warming trend. As the image indicates- the
open-set low-rise with a lot of trees and so forth is cooler than the regional average.
While built up areas are up to about 1.5 degrees warmer and the effect is more pronounced in
the winter season. Furthermore, the heating degree days a measure
of the heating need of a given locality is also dropping. In the last 30 years up to
about 12% drop in heating degree days can be seen in more built up areas of the city.
This too has energy and carbon implications and could be exploited for climate change
resilience approach in the city. The second aspect of our study is the intra-urban
variation. In order to do this we have established 6 weather stations across the city and its
surroundings. The image shows their approximate locations. And my colleague Dr Eduardo Kruger
who is a visiting researcher from Brazil who is involved in this study collaborating with
us will talk about the instrumentation for the intra-urban variations.
This is the instrumentation used for the intra-urban measurements. This is a datalogger, a tinytag,
and every time we programme this for recording data every 5 minutes. And later we can compile
data for hourly measurements. And this tinytag goes inside this box here, this is the so
called Stevenson Screen, where we have solar radiation protection and also rain protection.
So this is all closed with normal nuts and every time we set it up in different spots
of the city centre and hanging from a stick or hanging from a wall aperture, or from trees,
depending on the location. We have located 6 such stations in and around
the city of Glasgow, the first one COR1 is in the city centre, it’s at the Macintosh
school of architecture, located across the street canyon about 3 metres above the ground
level. The second one, COR2 is also located in the
city centre, it is at Miller Street on a very high street urban canyon. Approximately half
a metre from the ground level. The third station is in Glasgow green, in
a green area near a water body approximately 1.8m above the ground level.
Fourth station is in a residential area in the city centre, 1.2m above ground just south
of the river Clyde. We have two more stations, SUB1 and SUB2 – these
are also residential but in the suburban parts of the city near the edge of the city level
near Queens Park. The other stations are two just outside the city limits.
The results of our intra-urban variations in and around Glasgow indicates that there
is a clear heat-island effect in the city. The cooling rate at different sites are different
both between the sites as well as during the course of the day. Between sunset and sunrise,
some of the areas heavily built up have up to 1.2 degree warmer per hour than the regional
average. On the other hand, during the daytime it could be positive, in other words the city
has a “cool island” effect, given the blockages is causes to direct sunlight and
win and so forth. There are positive and negative variations between the day and the night as
well as between the sites themselves. The third aspect of our study is to look at
local street level micro-level variations. In order to do this, we employed a traverse
across the city core on a bicycle. Hello I’m Eduardo Kruger and I’m here
to present the setup that we use for the traverse measurements. So we have here the data logger
and it is in enclosed in this box which is a solar radiation shield. I have a mini fan
here to increase the wind speed. And in the end what we measure here is the air temperature
at different spots in the city centre. So what I’m usually doing - I go around
to around 15 spots within the city centre and at each spot I stay for more or less 2
minutes and within 5 minutes I’m in a different spot. And in the end I can put the measurements,
can draw the lines of temperature around each spot in a map; as shown in the presentation.
This is the weather station that measures meteorological parameters during our comfort
survey. The station is - even though it’s an officially recognised set of instruments,
it is set up in a way that measures the human experience of climate in a street canyon so
it is set up in a way that it can be easily dismounted and taken easily to the site. It’s
set up at a height which is corresponding to human experience of climate, it measures
temperature and humidity – it also measures wind speed and wind direction, furthermore
it measures global solar radiation that a person is likely to see at the street level.
It can also measure lighting level and rainfall, which is not used for this study. IT is powered
by a set of solar cells. We take it to the site while concurrently measuring – administering
a set of questionnaires for thermal comfort experience of people in the city streets.
Here is a plot of the Isolines of temperature in and around the city core area. We generated
this based on temperature measured at each street corner on a gridded pattern. You can
see here the city core is up to 2 degrees warmer on a day that we did this study – 7th
March this year. And using a reference station outside the city limits we could see the intra-urban
variations which are significant given the fact that this is the late winter, so 1 to
2 degree warmness depending on how built up the local area is, can be seen on the street
level climate variations. Hello this is the weather station which is our reference station
for all studies we are conducting here. This is located here on the roof of the Saltire
Centre and surrounded by buildings. This is the more or less like an urban setting and
we’re gathering data here regarding wind speed and direction, we have solar radiation
data, global solar radiation data recorded by this sensor. This is the solar cell which
powers that station and we also have temperature and humidity.
And in this case we’re also recording data regarding rain amount.
The outdoor thermal comfort study consists of measurements within the city centre and
along with the measurements with a portable weather station which has been shown before
we conduct a series of questionnaires with passers-by.
The questionnaires consist of 4 parts. First part I have information about the subject
– like gender, age, weight and height. Whether the subject lives in Glasgow or in the UK,
and how long has he spent outdoors. Second part consists of the clothing garments
the clothing insulation values as shown in table annex A of ISO 9920. Third part consists
of the thermal perception at the given moment of the interview. Part four is about the preference
– how would the person prefer to be at this moment?
This picture represents the points used for the thermal comfort study. So far we have
6 days of measurements and the measurements run from 10 to 1 and so far 165 questionnaires
filled. For each point we stayed three hours, interviewing people and measuring microclimate
data at the same time. The measurements add each point they will provide us with information
about the passers-by, thermal perception, and also micro-climate data that we can then
compare to the reference station. So far we have 6 days of measurements and
165 questionnaires filled. We now move to the final section of our presentation
which indicates some of our early findings and the implications for climate change and
resilience of cities. First implication is the urban heat island itself could be used
as acclimate change adaptation strategy. Unlike many cities with heat island problem, Glasgow
is in a happy situation of being able to exploit the unintentional warmness created by urban
growth. This has energy and carbon implications and especially the recently implications to
the district heating possibilities. If we could enhance the trapping of heat by the
judicious arrangement of buildings and the building geometry we could perhaps potentially
benefit the proposed district heating systems in the city core area.
Secondly there are also lessons to be learnt for the city of Glasgow for the wider global
climate change mitigation efforts. The amount of climate change witnessed by the city is
of the same order of magnitude to the expected global warming predicted over this century.
So lessons could be learned as to how we in this city have managed to adapt to this change
so that other cities could perhaps learn how to do the management themselves.
Finally there are also specific lessons to be learned from Glasgow as you will know Glasgow
is a shrinking city ,this is an urban transformation that will happen to all our major urban areas
even those that are currently growing. So regeneration and heat island could perhaps
have linkages. Knowing that these changes will happen perhaps the city of Glasgow could
be a test case to learn lessons for how regeneration and the urban heat island management could
be linked together. And perhaps we could look at how urban areas, while they shrink, they
could in a colder climate be designed in a such a way that the UHI effect itself does
not shrink, so that we can continue to benefit from the positive energy and carbon aspects
of this phenomenon. And that’s our presentation, thank you very
much for listening. This is an ongoing work and we would be happy to talk to you about
the current findings and the implications for a way forward.
Thank you.