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Title: Anthropogenic climate change and extreme weather events : implications for Bangladesh
Author: Rimi, Ruksana Haque
ISNI:       0000 0005 0291 3732
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2019
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Probabilistic Event Attribution (PEA) quantifies the change in risk of extreme weather events due to external drivers of climate change. The regional climate model (RCM) of the weather@home system has been successfully used for this purpose. So far, most PEA based studies have focused on extreme events of mid-latitudes and developed countries, while the events occurring in tropical regions and developing countries have gained little attention. This thesis evaluates the performance of the RCM of weather@home over the complex tropical monsoon climate region of South Asia, with particular focus on Bangladesh. In a combined process-based and performance-based evaluation process, first the model's response to observed variability of sea surface temperatures (SSTs) are assessed. Second, the RCM's skill to simulate the extreme events in Bangladesh is evaluated against observations. The results suggest that the RCM performs well, capturing both, influence of observed natural SST variations and extreme weather events in Bangladesh. The thesis uses large ensembles of weather@home RCM simulations for two studies. PEA is first applied to attribute contributions of past and future greenhouse gas (GHG) emissions to extreme events under current climate conditions and future warmer worlds. In accordance with the targets set out in the Paris Agreement, 1.5 and 2.0 degrees warming scenarios are investigated. Results indicate that the risk of seasonal extreme rainfall events across Bangladesh will increase with additional global warming. Anthropogenic aerosols are found to be a significant influencing factor along with GHG concentrations and large-scale temperature in determining the climate change impacts. The RCM based results are found to be consistent with the findings based on simulations from four other Atmosphere Only Global Climate Models (AGCMs) under the Half a degree Additional warming, Prognosis and Projected Impacts (HAPPI) project. PEA is secondly applied for an extreme pre-monsoon rainfall event of 2017 that occurred over north-east Bangladesh and caused flash flood and severe crop damage. According to this analysis, anthropogenic climate change is assessed to have increased the risk of such event occurring by more than a factor of 2. Findings of this thesis show that the RCM of weather@home system may provide a sufficiently reliable tool for attributing human impacts on the likelihood of extreme events over the complex tropical monsoon climate region of South Asia in general and Bangladesh in particular. Since anthropogenic climate change is found to be of crucial importance with regard to extreme weather events, the conclusions of this thesis will facilitate further attribution studies over the region and help to provide guidance for local policy makers as far as climate change adaption is concerned.
Supervisor: Allen, Myles Sponsor: Commonwealth Scholarship Commission
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Geography