Change Detection and Trend Analysis of Future Temperature and Rainfall over West Africa
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ORIGINAL ARTICLE
Change Detection and Trend Analysis of Future Temperature and Rainfall over West Africa Oluwaseun W. Ilori1 · Vincent O. Ajayi1 Received: 1 May 2020 / Accepted: 14 August 2020 © The Author(s) 2020
Abstract This paper examined future trends with change detection in temperature and rainfall over three agro-climatic zones of West Africa. Historical (1961–2000) and projection (2020–2099) data of ensemble-mean of six RCMs that dynamically downscaled five GCMs that participated in CMIP5 obtained from Co-Ordinated Regional Climate Downscaling Experiment (CORDEX) were used. Standard normal homogeneity, Buishand’s, Pettitt’s, and Mann–Kendall test were used for change point detection and trend analysis at 5% significant level. Inter-annual anomaly and projected change in the seasonal cycle relative to historical mean were investigated. The ensemble-mean evaluation performed for the historical period (1961–2000) using CRU dataset revealed that the change point occurred in rainfall and temperature series in the 1970s and 1980s, while a significant increasing trend is observed in temperature in all climatic zones. Change-point detection test projects rainfall series to be homogeneous as significant change point is expected to occur in temperature for all zones under RCP4.5 and RCP8.5 for near (2020–2059) and far-future (2060–2099). For the near-future, an increase in the mean temperature between 0.5–1.30 ℃ and 0.19–1.67 ℃ is projected to occur under RCP4.5 and RCP8.5 respectively. Projected relative change in seasonal cycle shows that winter months may witness increase in rainfall amounts under RCP4.5 but significantly dry under RCP8.5 in near and far-future as temperature is expected to become warmer in all months. Rainfall anomaly projects the Sahel to have a reduced amount of rainfall compared to other zones as temperature anomaly reveals a continuous increase in all the zones under the two RCPs. The results of this study show that climate change will intensify in West Africa in the future. Keywords West africa · CORDEX · Climatic zones · Change detection · Mann–kendall trend analysis · Regional climate models
1 Introduction Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) projected a continuous increase in global temperature (IPCC 2007a) as a result of: increasing fossil fuel combustion and greenhouse gases (GHG) emission, significant changes in land-use/land-cover due to industrialization and urbanization and natural processes like earthquake (IPCC 2007b). These natural processes and human-induced (anthropogenic) forces have contributed significantly to the modification of climate pattern (IPCC 2007a) over the world, leading to intensification * Oluwaseun W. Ilori [email protected] 1
Department of Meteorology and Climate Science, Federal University of Technology, Akure, PMB 704, Akure, Ondo State, Nigeria
of El~Nino events, increase in the occurrence of extreme weather events (Akinsanola and Zhou 2018; Gbode et al. 2019), increase in the ocean and land surface
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