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

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 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.

High‐Temperature Extreme Events Over Africa Under 1.5 and 2 °C of Global Warming

“…Although Africa is one of the regions projected to be hard-hit by the brunt of climate change (Niang et al, 2014), similar studies on the impacts of 1.5 and 2°C of global warming have been relatively limited in comparison to other parts of the world. However, in the recent past, there have been studies that employed regional climate models driven by global models from phase five of the Coupled Model Intercomparison Project (CMIP5; Taylor et al, 2012) in investigating climate risks at 1.5°C and/or 2°C warming levels over Africa (Klutse et al, 2018;Maure et al, 2018;Nikulin et al, 2018;Osima et al, 2018;Pokam Mba et al, 2018). The collective finding from these studies is that the 0.5°C upsurge in global warming from 1.5°C leads to insignificant increases in precipitation in most parts, especially in the subtropics.…”

The Köppen‐Trewartha Climate‐Type Changes Over the CORDEX‐East Asia Phase 2 Domain Under 2 and 3 °C Global Warming

“…However, GCMs have a weak point in resolution for reflecting the realistic impacts of local forcing with detailed topography or land use types Choi et al, 2016;Im et al, 2006Im et al, , 2007Im et al, , 2015Lee & Hong, 2014). Therefore, numerous dynamically downscaled climate change assessments at the target GWL based on the regional climate model (RCM) have actively been carried out in line with the Coordinated Regional Climate Downscaling Experiment (CORDEX) project: Donnelly et al (2017), Dosio and Fischer (2018), Jacob et al (2018), and Marx et al (2018) for the EURO-COREX domain;and, Nikulin et al (2018), Maúre et al (2018), Mba et al (2018), and Lennard et al (2018) over the CORDEX-Africa domain.…”

Potential impacts of specific global warming levels on extreme rainfall events over southern Africa in CORDEX and NEX‐GDDP ensembles

“…Schleussner et al (2016) found a 2% increase in the intensity of heavy rainfall between a 1.5 and 2.0 C globally and a 3% increase over South Asia. However, Rogelj et al (2015) warned that limiting the warming to below 1.5 C may require greater mitigation efforts and higher mitigation costs than keeping it at 2.0 C. Over Africa, some studies found higher impacts at 2.0 C GWL than at 1.5 C (Diedhiou et al, 2018;Klutse et al, 2018;Maúre et al, 2018;Mba et al, 2018;Nikulin et al, 2018;Osima et al, 2018;Weber et al, 2018;Tamoffo et al, 2019). For example, Weber et al (2018) found that rainfall intensity is likely to increase under a higher global warming scenario, especially over the sub-Saharan coastal regions.…”

“…Both CORDEX and NEX datasets are freely available for regional climate change studies. However, while a few studies have discussed COR-DEX projections over southern Africa (e.g., Déqué et al, 2017;Maúre et al, 2018;Nikulin et al, 2018), thus far, no study has examined NEX projections over the subcontinent. For instance, analysing the CORDEX dataset at a 2.0 C warming level, Déqué et al (2017) projected fewer rain days but more intense rain over the tropical southern Africa.…”