Climate Change Trends, Projections and Vulnerability Integration to Enhance Urban Resilience Planning: The case of Addis Ababa City
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Date
2019-02
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EiABC
Abstract
Impacts of climate change continue to knock on the doors of different societies including
urban dwellers. The effect is more severe in towns of developing world like Addis Ababa
where level of mitigation and adaptation measures are low and detailed climate change
information is lacking. Many of existing studies give no consideration to the future
climatic conditions, spatial quantification and mapping of vulnerability hotspots and
integration of these all together for enhanced resilience planning. They mainly focused
on basic environmental plans, where most of them fail implementation due to low level
of law enforcements and unavailability of up to dated cadastral information system.
Taking these points into considerations, this study focuses on analyzing climate change
trends, downscaling projected results from general circulation models, analyzing land
surface temperature changes, quantifying and mapping climate change vulnerability at
sub-city level to recommend better environmental planning options which could be
implemented to minimize severe climate change risks at Addis Ababa city. To achieve
these, various methodological approaches were applied in a sequential order. Using
Statistical Downscaling Model (SDSM), downscaled daily maximum temperature,
minimum temperature, and precipitation in 30 years intervals from the second generation
of the Earth System Model (CanESM2) and Coupled Global Climate Model (CGCM3)
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under two Representative Concentration Pathways (RCP) Scenarios (RCP4.5 and
RCP8.5) and two Special Report Emission Scenarios (SRES), A1B and A2, were
generated to examine future changes and their extremes. Two representative
meteorological stations were selected for model calibration and validation in the SDSM.
With this, ten core temperature and precipitation indices were selected to assess
temperature changes and precipitation extremes. Spatio-temporal Land Surface
Temperature (LST) characteristics were analyzed using four Landsat satellite image
series with ten years interval from 1986 to 2017. Sub-city level Climate change
vulnerability analyses were undertaken by integrating the Sullivan and Meigh’s Model of
composite climate change vulnerability index and the IPCC’s approach of vulnerability
assessment which comprises exposure, sensitivity and adaptive capacity. Fifteen
subcomponents of vulnerability indicators were identified in ten sub-cities, and their
values were normalized to a number which ranges between 0 and 1, with unequal
weighting system, indicating as the values increased to 1, vulnerability to climate change
increases. The results were mapped using ArcGIS 10.2 package. In-depth empirical
field work including a survey of 399 households in four sub-cities and key informant
interviews were conducted and analyzed using descriptive statistics and Chi-squared tests
were used to summarize the findings in SPSS. Finally climate change resilience plans
were proposed for a sustainable environmental protection and to reduce the vulnerability
that could be induced by climate change. The results showed that maximum temperature,
minimum temperature and mean temperature was increasing in the last 60 years. The
second thirty years mean temperature average, was higher than the first thirty years
average by 1.1 ºC within 1957-2016. The trend in precipitation shows only insignificant
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rise wihin the last six decades. The projected maximum temperature, increases were in
the range of 0.9ºC (RCP4.5) in 2020 to 2.1ºC (CGCM3A2) in 2080 at Addis Ababa
Observatory. The minimum temperature is projected to increase by 0.3ºC (RCP4.5) in
2020 and 1.0 ºC in 2080 (CGCM3A1B). While the changes in maximum temperature are
lower at Entoto station compared to Addis Ababa Observatory, the highest minimum
temperature change is projected at Addis Ababa Observatory, which ranges from 0.25ºC
in the 2020s to 1.04ºC in 2080 according to the CGCM3 model. Except for the coldest
nights (TNn), the mean temperature and other temperature indices will continue to
increase to the end of this century. The highest precipitation change is projected by
CGCM3A2 and CanESM2 RCP8.5 at an increase of about 11.8% and 16.62% by 2080.
The highest total precipitation increase is 29% (RCP4.5) in winter and 20.9% (RCP8.5)
in summer by 2080. The rise in temperature will exacerbate the urban heat highland
effects in warm seasons and an increase in precipitation is expected along with a possible
risk of flooding due to a low level of infrastructure development and a high rate of
urbanization. It is also found that land surface temperature was highly influenced by land
cover types. The highest LST was found in built-up areas and barren lands. 49% and
47% of the study area had an LST range of 23°C - 27°C in 1986 and 1995 respectively.
However, in 2007 and 2017, 41% and 59% of the study area had LST range of 27°C -
31°C respectively. The ten sub-cities in Addis Ababa were found in different levels of
vulnerability to climate change with the highest exposure and sensitivity in Addis
Ketema, Arada, and Lideta while the adaptive capacity was highest in Gulelle, Bole, and
Arada sub-cities. The overall climate change vulnerability was highest in Arada, Addis
Ketema and Kirkos. The result also found that 69.2% and 60.2% of the respondents
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perceived that temperature and precipitation increased within the last one to three decades
respectively. Flash flood during high precipitation is common along the main roads in
Kirkos, while river flooding is a major problem in summer for the residents living along
the sides of Akaki River where the cost of damage is high sometimes to the loss of all
property and life too. The study recommended city level and landscape level resilience
plans within Addis Ababa and the surrounding mountainous landscapes.
Description
This is to certify that the dissertation prepared by Nahimi Feyissa, entitled: Climate
Change Trends, Projections and Vulnerability Integration to Enhance Urban Resilience
Planning: The case of Addis Ababa City and submitted in fulfillment of the requirements
of the Degree of Doctor of Philosophy (Environmental Planning) compiles with the
regulations of the University and meets the accepted standards with respect to originality
and quality.
Keywords
Climate Change, General Circulation Models, Statistical Downscaling Model, Resilience Plans, Urban Heat Island, Vulnerability Index