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) iv 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 v 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 vi 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

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