Assessment of Past and Future Climate Change as Projected by Regional Climate Models and Likely Impacts Over Kenya
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Date
2019-05
Authors
Sagero, Philip Obaigwa
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
Climate change and variability is one of the global challenges that is affecting development worldwide. In the recent time, Regional Climate Models have been relied upon to give high-resolution climate projection at a local scale for impact assessment and development of adaptation strategies. These models are used to downscale the Global Climate Models which are used in the preparation of Intergovernmental Panel on Climate Change assessment reports. To provide local scale information for impacts assessment, vulnerability analysis and adaptation strategies, projection of future climate change must be of high resolution. This study was able to assess the past and future projections in climate as projected by the Coordinated Regional Climate Downscaling Experiment, Regional Climate Models, with a 50 km spatial resolution over Kenya. To achieve the objective of the study, analysis of the past rainfall and temperature pattern and trends over Kenya was done using observed station data and gridded datasets. The skill of the models to simulate the observed pattern and variability was determined using gridded datasets (Global Precipitation Climatology Center and Climate Research Unit) for both rainfall and temperature (minimum and maximum). Interannual rainfall variability over Kenya is controlled by large-scale systems, therefore the ability of the models to capture these teleconnections was analyzed by use of the composite method. After testing the skills and abilities of the regional models, then an assessment of the future changes on rainfall and temperature as projected by the models under Representative Concentration Pathways (RCP) 4.5 and 8.5 emission scenarios was done. Also, the future change in climate extreme was also analyzed by use of climate extreme indices. Finally, an analysis of the likely impacts of the projected changes on different sectors of the economy over Kenya was also done. The results show that rainfall and temperature over Kenya is variable from one place to another. The regional models were able to simulate rainfall and temperature well over Kenya. They also capture well the spatiotemporal patterns of rainfall and temperature over Kenya. An increase in temperature of about 5 oC is projected by the end 21st Century under RCP4.5 and RCP8.5 scenario. The minimum temperature is expected to increase more than maximum temperature thus increase/decrease in warmer/colder nights. All the models 0show a better agreement on temperature projections. 70% of the models projected a decrease in March April May rainfall and an increase in October November December rainfall under RCP8.5. And a decrease in both season under RCP4.5. There is no significant change in the precipitation extreme indices except for Consecutive Dry Days and Consecutive Wet Days which are projected to increase and decrease respectively. Nevertheless, there is a clear decrease in annual precipitation totals. The models project high rainfall variability with a small shift of increasing trend. These projected changes will negatively impact agriculture, health, water and energy sectors and there is need for development of adaptation strategies at local level. The findings of the study can be used by government to develop adaptation strategies that will increase resilient of local communities. The models were not coherent in their rainfall projection, therefore further studies should be carried out on based on an ensembled model and the physics of the models should also be looked at, to find out whether the mesoscale system that affects rainfall over Kenya are well included in the models.
Description
Thesis Submitted in Fulfillment of the Requirements for the Award of the Degree of Doctor of Philosophy in Climatology in the School of Pure and Applied Science, Kenyatta University