The southern African climate under 1.5 °C and 2 °C of global warming as simulated by CORDEX regional climate models

G Maúre,M Ndebele-Murisa,I Pinto,M Muthige,A Dosio,A Meque,C Lennard,G Nikulin

doi:10.1088/1748-9326/aab190

Abstract

Results from an 25 regional climate model simulations from the Coordinated Regional Downscaling Experiment Africa initiative are used to assess the projected changes in temperature and precipitation over southern Africa at two global warming levels (GWLs), namely 1.5 °C and 2.0 °C, relative to pre-industrial values, under the Representative Concentration Pathway 8.5. The results show a robust increase in temperature compared to the control period (1971–2000) ranging from 0.5 °C–1.5 °C for the 1.5 °C GWL and from 1.5 °C–2.5 °C, for the 2.0 °C GWL. Areas in the south-western region of the subcontinent, covering South Africa and parts of Namibia and Botswana are projected to experience the largest increase in temperature, which are greater than the global mean warming, particularly during the September–October–November season. On the other hand, under 1.5 °C GWL, models exhibit a robust reduction in precipitation of up to 0.4 mm day−1 (roughly 20% of the climatological values) over the Limpopo Basin and smaller areas of the Zambezi Basin in Zambia, and also parts of Western Cape, South Africa. Models project precipitation increase of up to 0.1 mm day−1 over central and western South Africa and in southern Namibia. Under 2.0 °C GWL, a larger fraction of land is projected to face robust decreases between 0.2 and 0.4 mm day−1 (around 10%–20% of the climatological values) over most of the central subcontinent and parts of western South Africa and northern Mozambique. Decreases in precipitation are accompanied by increases in the number of consecutive dry days and decreases in consecutive wet days over the region. The importance of achieving the Paris Agreement is imperative for southern Africa as the projected changes under both the 1.5 °C, and more so, 2.0 °C GWL imply significant potential risks to agricultural and economic productivity, human and ecological systems health and water resources with implied increase in regional water stresses.

Highlights

The Paris Agreement which was achieved in December 2015 holds signatory countries responsible for keeping the increase in global average temperatures well below 2.0 ◦C and under 1.5 ◦C below the preindustrial period recognizing that ‘this would significantly reduce the risks and impacts of climate change’
Using a Coordinated Regional Downscaling Experiment (CORDEX) ensemble of regional climate models (RCMs) and the R package RClimDex for calculating precipitation indices, studies show that the western part of southern Africa is projected to become drier with drought frequency and number of heat waves increasing towards the end of the 21st century under the A2 scenario (Engelbrecht and Engelbrecht 2016) and under both Representative Climate Pathway (RCP) 4.5 and RCP 8.5 (Dosio 2017)
Given the signals of warmer and more arid conditions that have been noted over the past few decades and across most parts of southern Africa (Morishima and Akasaka 2010), this paper examines the potential impacts of climate change on temperature and precipitation under 1.5 ◦C and 2.0 ◦C global warming levels over southern Africa using a large ensemble of RCMs from the CORDEX

Summary

Introduction

The Paris Agreement which was achieved in December 2015 holds signatory countries responsible for keeping the increase in global average temperatures well below 2.0 ◦C and under 1.5 ◦C below the preindustrial period recognizing that ‘this would significantly reduce the risks and impacts of climate change’. Using a Coordinated Regional Downscaling Experiment (CORDEX) ensemble of regional climate models (RCMs) and the R package RClimDex for calculating precipitation indices, studies show that the western part of southern Africa is projected to become drier with drought frequency and number of heat waves increasing towards the end of the 21st century under the A2 scenario (Engelbrecht and Engelbrecht 2016) and under both Representative Climate Pathway (RCP) 4.5 and RCP 8.5 (Dosio 2017) Such strong signals of warming and drying have been shown to be consistent with most of the Coupled Model Intercomparison Project Phase 3 (CMIP3) and Coupled Model Intercomparison Project Phase 5 (CMIP5) (Taylor et al 2012) Global Climate Models (GCMs) and are attributed to the projected future strengthening of the subtropical highs and the mid-level anticyclonic circulation under low mitigation scenarios (Christensen et al 2007, Engelbrecht et al 2009, Engelbrecht et al 2015, Dequeet al 2017)

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Discussion

Conclusion