However, significant biases persist in climate models regarding the representation of monsoon systems, and projections of their future evolution remain uncertain. Improving our understanding of the mechanisms driving monsoon circulations, land–atmosphere interactions, and convection processes is therefore essential to enhance the simulation of monsoon systems and climate across Africa.
This session welcomes contributions on all aspects of African climate, on Past climate over African, S2S to decadal prediction, centennial changes, and work emphasising physical processes and numerical modelling. We also welcome studies on climate-related applications using Natural Language Processing and other ML/AI techniques. We invite presentations on operational applications and observational networks. Papers which connect African climate change and variability to human health, food and water security, and socio-economic development are welcome.
Orals: Mon, 4 May, 10:45–12:30 | Room 0.31/32
Northern Namibia lies in a climatically sensitive transition zone, yet its hydroclimate across multiple glacial–interglacial cycles remains poorly constrained. We present a regional speleothem dataset from ten caves in the Otavi Mountains, comprising about 55 speleothems and ~200 U-Th dates, spanning four glacial–interglacial cycles. Vadose speleothem deposition is strongly biased toward glacial periods, with no growth recorded during pre-Holocene interglacials and only limited Holocene deposition restricted to a few caves.
In contrast, submerged caves from the same region document a pronounced rise in groundwater levels beginning around 15 ka BP, providing compelling evidence for increased effective infiltration since the late glacial. The near-absence of vadose speleothem growth during interglacials despite elevated groundwater levels presents a fundamental paradox. We propose that high cave-air pCO₂ during warm interglacial conditions suppressed calcite precipitation in the vadose zone by limiting CO₂ degassing, even under increased recharge. This interpretation is supported by modern observations from caves in the Otavi Mountains today, which exhibit high to very high cave-air CO₂ concentrations and little to no active stalagmite growth.
By integrating vadose speleothems with subaqueous records of groundwater-level change, this dual-archive approach provides a powerful framework to reconstruct Namibia’s paleo-hydroclimate and to disentangle the roles of effective infiltration and cave-atmosphere dynamics on centennial to orbital timescales.
How to cite: Spötl, C., Boekholt, M., Leitgeb, L., Dublyansky, Y., Koltai, G., Zhang, H., and Cheng, H.: A Dual Speleothem Perspective on Glacial–Interglacial Hydroclimate in Northern Namibia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14091, https://doi.org/10.5194/egusphere-egu26-14091, 2026.
Hydroclimate variability in northern Africa, driven by the interactions between the mid-latitude westerlies and the West African Monsoon (WAM) and by variations in their intensity, represents a key control on hominin dispersal. However, the response of these atmospheric circulation systems to changing boundary conditions and their influence on precipitation during past climate states remain poorly constrained, largely because most well-dated terrestrial hydroclimate records are limited to the Holocene interglacial period. Here, we present a 300,000-year hydroclimate record from northernmost Africa based on speleothem growth in Tunisia. This record captures alternating humid and arid phases across multiple glacial–interglacial cycles, as well as superimposed millennial-scale variability. Speleothem growth occurred predominantly during interglacials, indicating humid conditions, whereas growth hiatuses correspond to arid glacial periods. The cave record suggests that humid phases in northernmost Africa were primarily driven by a southward displacement and intensification of the mid-latitude westerlies and the Mediterranean storm track during interglacials. Comparison with Saharan palaeolake records further indicates that both enhanced winter westerlies and a strengthened summer WAM were required to generate widespread wet conditions across northern Africa during interglacial periods. These results highlight the combined influence of winter and summer moisture sources in shaping long-term hydroclimate variability and defining habitable corridors across northern Africa over the past 300,000 years.
How to cite: Chung, Y., Dhaouadi, H., Marino, G., Sbei, E., Seppä, H., Kaakinen, A., Lone, M. A., Ouezdou, H. B., Frisia, S., and Shen, C.-C.: Three Hundred Thousand Years of Multi-Millennial Hydroclimate Variability in Northern Africa Revealed by Tunisian Speleothems , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5152, https://doi.org/10.5194/egusphere-egu26-5152, 2026.
Lake Tanganyika, the world’s longest and second deepest lake, is shared by Burundi, Tanzania, Zambia, and the Democratic Republic of the Congo. Located in a region where resources can be limited, the lake and its fishery serve as vital sources of protein, freshwater, and economic development for 12 million people living within its catchment. Unfortunately, over the past several decades, the lake has experienced declines in biodiversity, natural habitat, and economic utility, most clearly evident in reduced fish catch rates. The causes of this decline are complex and still debated, but they may include changing fishing practices, climatic variability, and land use. This project seeks to uncover the historic drivers of nutrient cycling in the lake to determine which factors ultimately govern its fishery productivity. In this study, we use oxygen isotopes in phosphate and isotopes of carbon and nitrogen from sediment cores covering the past 2,000 years to explore how internal lake processes have been influenced by human activity and environmental processes. The findings aim to inform sustainable fishery management strategies.
How to cite: Streib, L., McGlue, M., Latimer, J., Price, J., Liu, X., and Waldmann, N.: Influences on nutrient cycling within Lake Tanganyika, eastern Africa, during the Common Era inferred from sedimentary geochemistry, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-991, https://doi.org/10.5194/egusphere-egu26-991, 2026.
Ongoing excavation missions at the Gcwihaba caves are continuing to identify new areas that are rich in archaeological and paleontological deposits. This includes the recent uncovering of new fossil micromammal assemblages from four distinct units within the cave —three stratified levels, likely of Holocene age, from the Deep Chamber and one unit of probable Pleistocene age from the Corridor area. The study of these remains provides an opportunity for a diachronic comparison of the faunal composition and taphonomic signature of the bones pending further absolute dating. This presentation offers first insights from the examination of these micromammal remains with the aim of understanding the site formation processes and tracing the past environmental and climatic changes over time in the northwest region of Botswana.
The study of fossil micromammals accumulated in cave sites has increasingly been used to reconstruct past landscapes and climatic changes over time. Because of their diversity, short lifespans, small home ranges, relatively precise habitats, and sensitivity to fluctuations in climate and vegetation, they are considered key indicator taxa. However, despite all this significance, the remains of this faunal group are still very little studied in Botswana.
We first performed a taphonomic investigation of the fossils in order to understand the processes responsible for the accumulation and preservation of the remains. We did this by assessing and analysing the relative abundance of skeletal elements, breakage patterns, and digestion modifications on each of the assemblages. We compared our results with patterns quantified on a modern barn owl bone accumulation collected from the cave. This step allowed us to ascertain which predator/(s) had been responsible for the accumulation of this fossil assemblage. The preliminary comparison of taphonomic results indicated some similarities in terms of the accumulating agent.
Following this, we performed taxonomic identification of the cranio-dental remains to assess and classify the species present in the samples. Both the fossil and modern assemblages show the presence of taxa belonging to at least four mammalian orders: Rodentia (rodents), Eulipoptyphla (shrews), Macroscelidea (elephant shrews), and Chiroptera (bats). The presence of taxa associated with specific habitat types can provide preliminary paleoenvironmental indications under the principle of actualism. Thus, the species variations observed over time can be interpreted in terms of climate and environmental changes. Considering this, the subsequent phase will be the application of a range of paleoecological methods to investigate the evolution of the environments surrounding the cave from the Pleistocene to the present.
How to cite: Claeys, O., Fourvel, J.-B., Thabard, C., Bruxelles, L., and Linchamps, P.: Micromammal Assemblages from Gcwihaba caves, Botswana: First insights on the taphonomy and paleoenvironments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-968, https://doi.org/10.5194/egusphere-egu26-968, 2026.
As Earth's largest desert, the Sahara experienced recurrent greening phases in the geological past, which has nurtured the earliest human civilizations. Understanding the occurrence of these Green Sahara periods (GSPs) and their driving mechanisms is crucial for reconstructing climatic history and predicting future climate trends. Traditionally, orbital forcing, particularly precession, has been considered the main control. However, geological records indicate that the occurrence of GSPs does not strictly follow orbital pacing, but instead exhibits prolonged absences (the skipped GSPs) during specific intervals. To investigate their cause, we conducted a series of climate sensitivity simulations quantifying different forcings in contributing GSPs. Results reveal that atmospheric CO2 and ice sheet extent also play a modifying role. Using quantitative estimation, we developed a simple but powerful theoretical model to estimate the pace of GSPs. In agreement with geological records, our theoretical reconstruction suggests that the skipped GSPs represent a persistent phenomenon throughout the Quaternary. Furthermore, we predict that the Sahara will probably not regreen within the next precession cycle unless the cumulative atmospheric CO2 emissions reach ~3,840 Petagrams of Carbon (Pg C). These findings provide a scientific basis for reconstructing Saharan paleoclimate and offer valuable insights for predicting its future climate change.
How to cite: Wang, H. and Yang, H.: Occurrence rhythms and mechanisms of Green Sahara periods over the Quaternary, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11631, https://doi.org/10.5194/egusphere-egu26-11631, 2026.
During the recovery from the depths of the 1980s drought, extreme rainfall in the Sahel has increased faster than the mean seasonal rainfall, so that currently more than a third of the summer rainfall falls in the form of deluges.
Tracking storms in a combination of satellite-based rainfall and emission temperature data shows that, from the early 1980s to the late 2000s, the increase in extreme rainfall fraction was the consequence of the strongest storms becoming more frequent, likely because the enhanced warming of the Sahara produced enhanced thermal wind and wind shear, which better supported the development of well-organized Mesoscale Convective Systems with very intense convective towers.
However, since the late 2000s, the number of strong storms has plateaued: warming continued to intensify in the Sahara, but the anomalous temperature gradient moved north, leading to reduced shear in the key storm development region. The intensity of the strongest convection, as measured by the coldness of the cloud tops, also stopped increasing.
Yet, extreme rainfall has kept increasing apace. We interpret this as a thermodynamic effect: influenced by warming ocean waters in the tropical Atlantic and the Mediterranean, moisture levels have been rising throughout the region and throughout the depth of the atmosphere, leading to heavier rainfall being produced by the same convective intensity.
How to cite: Biasutti, M., Spät, D., and Voigt, A.: Rainfall Recovery in the Sahel: the Roles of Storm Frequency, Intensity, and Efficiency. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3606, https://doi.org/10.5194/egusphere-egu26-3606, 2026.
Monitoring Sahelian rainfall variability is increasingly critical as climate extremes intensify across the region. Here, we develop the Sahelian Monsoon Ocean-Pressure Index (SMOPI), a new global synthetic index constructed from five dynamically coherent sea-level pressure regions statistically linked to June-September Sahel monsoon rainfall (Tamoffo et al. 2025). SMOPI portrays intra-seasonal and interannual variability, and crucially, reflects the influence of both regional processes and large-scale teleconnections on monsoon dynamics. SMOPI aligns with the dominant rainfall variability mode both in reanalyses and 29 CMIP6 models. Strong/positive SMOPI phases coincide with wet years and are associated with enhanced convergence, favorable jet configurations, and robust Pacific, Atlantic, and Indian Ocean teleconnections. Conversely, weak/negative SMOPI phases correspond to drought conditions and divergent moisture fluxes. SMOPI exposes climate model failures in reproducing historical droughts and offers new physical insights into rainfall-driving mechanisms. It has a potential to be a scalable, transferable diagnostic tool for monitoring, forecasting, and evaluating Sahelian monsoon rainfall under global warming.
Tamoffo, A.T., Weber, T., Mouassom, F.L. et al. The global Sahel monsoon ocean-pressure index reconciles its regional and large-scale features. npj Clim Atmos Sci 8, 323 (2025). https://doi.org/10.1038/s41612-025-01226-2
How to cite: Tamoffo, A., Weber, T., Mouassom, F., Le-Roy, B., Teichmann, C., Jacob, D., Dosio, A., and Akinsanola, A.: The global Sahel Monsoon Ocean-Pressure Index reconciles its regional and large-scale features, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3814, https://doi.org/10.5194/egusphere-egu26-3814, 2026.
The Congo Basin in Central Africa remains one of the few regions globally where the Intergovernmental Panel on Climate Change (IPCC) has not reported observed trends in hot extremes or attributed such changes to anthropogenic influences, primarily due to the scarcity of in situ observational data. Similarly, observed changes in extreme daily precipitation since the 1950s have not been assessed for this region. Although extensive daily weather records exist, spanning from the 1900s to the early 2000s and covering numerous stations across the basin, the majority of these remain archived on paper, limiting their accessibility for climate analysis. Here, we present our historical weather data rescue project entailing archived data from 37 weather stations in the Democratic Republic of the Congo (DRC). We outline the digitization process of these archival records, comprising over 1 million individual observations, and describe the subsequent transcription using MeteoSaver version 1.1. From these records, we construct daily time series of daily maximum, minimum, and average temperatures, precipitation, as well as dry bulb and wet bulb temperatures measured at three times per day (06:00, 15:00, and 18:00). This newly transcribed dataset provides a critical foundation for undertaking hydroclimatic trend analysis in the Congo Basin, one of the world’s most data-scarce yet climatically significant regions. Using this data, we conduct an analysis of multi-decadal temperature trends across the basin. Our findings reveal a consistent and accelerating warming signal since the 1960s, characterized by a rightward shift in the distribution of daily maximum, minimum, and average temperatures with each successive decade. Median trends across the stations are 0.24°C, 0.09°C, and 0.18°C per decade for daily maximum, minimum, and average temperatures, respectively, corresponding to approximately 0.7°C, 0.3°C, and 0.6°C of warming over 30 years. We further find an increasing frequency of hot extremes and a decreasing frequency of cold events with each successive decade during the period 1960-1990, across the aggregated station data. Specifically, the most recent decade exhibits approximately twice as many hot days per year and about half as many cold days compared to the earliest decade. Overall, this analysis of newly digitized historical weather data for the DRC highlights the urgent need to close the knowledge gap on climate trends in the Congo Basin.
How to cite: Muheki, D., Hufkens, K., Jacobsen, K., Verbeeck, H., Boeckx, P., Kankonde Ntumba, D., Kapalay Moulasa, O., Vercruysse, B., M. Birkholz, J., Verbruggen, C., Hawkins, E., Lampe, S., Kasongo Yakusu, E., Makanzu Imwangana, F., Mbifo, J., Besango Likwela, T., Meunier, F., Dewitte, O., Thorne, P., and Thiery, W.: From Paper to Proof: Revealing Congo Basin Warming Through Rescued Climate Archives, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10837, https://doi.org/10.5194/egusphere-egu26-10837, 2026.
This study provides a first analysis of future changes in mean and extreme precipitation over Northeast Africa and the Arabian Peninsula. To this aim, we exploited projections from ten selected CMIP6 models (in part I) under various SSP greenhouse gases emission scenarios for the mid to late 21st century. We found a north-south differentiation in future changes in total precipitation for the JF and MAM seasons, with decreases in the north and moderate increases elsewhere, although model uncertainties are high, particularly for MAM. In contrast, the JJAS and OND seasons show larger positive changes with less model uncertainty. These increases in mean precipitation will be accompanied by an increase in the intensity and frequency of extreme precipitation events. In addition, the JJAS (+6.7%) and OND (+4.5%) seasons will contribute more to cumulative annual precipitation, while the JF (-1.3%) and MAM (-9.9%) seasons will experience a reduction. Over Djibouti, where the selected models are shown to perform well, downscaled and bias-corrected CMIP6 data using the CDF-t method indicate in addition that the return period of intense precipitation events (≥ 80 mm/day) causing documented flooding will decrease from 5 years historically to 1.4 years by the end of the 21st century under the SSP5-8.5 scenario. This robust result indicates the need to strengthen flood adaptation measures in Djibouti. Furthermore, similar downscaling exercises are recommended for other sub-regions in Northeast Africa and Arabia, given the consistent trend towards higher intensity rainfall.
How to cite: Mohamed Waberi, M., Camberlin, P., Pohl, B., Blanchet, J., and Assowe Dabar, O.: Future changes in mean and extreme precipitation over North-East Africa and Arabia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16464, https://doi.org/10.5194/egusphere-egu26-16464, 2026.
As with many regions in the world, southern Africa strongly relies on seasonal rains for livelihoods, ecosystems, food and water security, therefore understanding rainfall changes is vital for adaptation planning and climate service practitioners. Future changes in rainfall over southern Africa are highly uncertain, with different global climate models projecting wetter, drier and shifted rainfall seasons. Taking an ensemble average suggests poor model agreement on the direction of change and therefore a low mean change that is not statistically robust. Ensemble averages also blur boundaries between different sources of uncertainty and obscure significant aspects of rainfall over this region that we have a better (or at least reasonable) understanding and confidence about. Analysis focussing on large ensemble averages often does not account for the significant internal variability in the climate, which we find to be very large for this region.
We will show results from a recently published study (Kennedy-Asser et al., Climatic Change, 2026), using over 200 different global climate model simulations from CMIP5, CMIP6 and UKCP18 (global runs used for UK Climate Projections), highlighting how important internal variability has been in the past and continues to be in the future for southern Africa. All models are imperfect, each have strengths, weaknesses and significant biases that prevent us from fully constraining potential futures. By reframing analysis around temporal variability, we show there is better model agreement on scenarios of low change, where the future remains within the range of historic variability, than there is on significant change towards wetting or drying in future.
In addition, by analysing models individually, it is possible to construct Climate Process Chains and Climate Storylines that explain the mechanisms behind simulated responses and plausibly justify the divergent model signals. We will present results from an in-depth analysis of outputs from multiple ensemble members across four CMIP6 models that show contrasting futures for this region (CanESM5, CNRM-ESM2-1, HadGEM3-GC31-MM, IPSL-CM6A-LR). We explore linkages between regional rainfall and Indian Ocean sea surface temperatures, pressure systems, ENSO teleconnections and changes in the Angola Low, and demonstrate how these changes could result in wetting, drying or delayed rainfall seasons. Framing the analysis in this way highlights some important climate states and drivers that may be indicative of future change in seasonal rainfall in one direction or another.
This research is part of an interdisciplinary project, SALIENT (https://www.climatebristol.org/projects/salient/), combining climate science and modelling findings presented here with insights from risk communication research and structured expert judgement. Novel insights on the interdisciplinary research process and of policy relevance will also be presented.
How to cite: Kennedy-Asser, A., James, R., Daron, J., Craig, A., Jack, C., Wolski, P., and Jones, R.: Making sense of uncertainty: insights into temporal variability and drivers of change in southern African rainfall, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15521, https://doi.org/10.5194/egusphere-egu26-15521, 2026.
Internal climate variability is a major source of uncertainty in decadal predictions of summer rainfall in the Sahel, where it can amplify or attenuate the impact of anthropogenically forced changes. Yet, its complexity and inherent randomness make it difficult to interpret, communicate, and integrate into decision-relevant information.
Here we introduce a novel framework to construct physically plausible storylines of internal variability (IVSs), based on a large set of multi-model large ensembles, which provides a robust sampling of internal variability and model uncertainty. Selecting Pacific Decadal Variability (PDV) and Atlantic Multidecadal Variability (AMV) as remote drivers of Sahelian climate, we identify coherent trajectories of internal variability that are physically interpretable.
We find that the proposed IVSs capture - and separate - a range of plausible near-term, decadal futures shaped by Atlantic and Pacific variability patterns, shedding light on the dynamics that modulate decadal rainfall regimes. In particular we identify a high-impact storyline of a positive AMV in-phase with a negative PDV leads to wet anomalies which roughly double the forced response over the Western Sahel, while the contrasting storyline largely offsets the effect of climate change in this region.
By combining physical understanding with robust statistical methods and multi-model large ensembles, the proposed method seeks to bridge the gap between climate science and action, providing more interpretable and decision-relevant regional climate information.
How to cite: Mindlin, J., Mex, J., and Kretschmer, M.: Internal Variability Storylines for near-term Summer Rainfall in the Sahel, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15293, https://doi.org/10.5194/egusphere-egu26-15293, 2026.
Using the gridded monthly Global Precipitation Climatology Centre (GPCC) version 2022 dataset, together with National Centers for Environmental Prediction (NCEP) R1 reanalysis data and Hadley Centre sea surface temperature (SST) data, we conducted a diagnostic analysis of the interannual variability of the leading modes of seasonal rainfall over southern Africa for the period 1950–2020. Although several modes were identified, only the first four modes are analyzed for each season considered (SON, DJF, MAM, and JJA). Because unrotated modes may be physically ambiguous or represent spurious patterns, a varimax orthogonal rotation was applied. This rotation maximizes the variance within localized regions of the domain, thereby enhancing the physical interpretability of the modes. The characteristics and associated climate signals of the four rotated modes are examined in this study. During austral spring (SON), the first mode exhibits a dipole-like structure, with strong positive loadings over most of SAF and weak or negligible loadings over the coastal regions of South Africa and southern Mozambique. This mode appears to be primarily associated with ENSO variability, with a weaker secondary connection to the Indian Ocean Dipole (IOD). The second mode displays a diagonal dipole-like pattern across SAF, resembling a La Niña–type rainfall response. The third mode shows a tripole-like structure, characterized by positive loadings over the core monsoon region of southeastern SAF and negative loadings on either side, and is linked to the Subtropical Indian Ocean Dipole (SIOD). The fourth mode presents a zonal tripole-like pattern, with positive loadings over central-western SAF and negative loadings over northern and southern SAF. All four leading modes are present across the four seasons considered, although their relative contributions and the sign and magnitude of their loadings vary seasonally. The associated SST patterns are consistent with known large-scale circulation anomalies linked to these climate modes. This analysis improves the understanding of the dominant drivers of seasonal rainfall variability over southern Africa and provides a useful framework for interpreting regional climate variability and potential predictability.
How to cite: Silverio, K. and Ambrizzi, T.: Interannual Variability of the Leading Seasonal Rainfall Modes over Southern Africa, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16458, https://doi.org/10.5194/egusphere-egu26-16458, 2026.
Central Western Africa lacks suitable paleoclimate proxy records and Gabon is no exception. Two stalagmites collected in June 2023 from Grotte de Camp Malheur located in the Ngounie Province of SW Gabon were used to reconstruct palaeorainfall records for the region over the past two centuries. Layer counts conducted by eye are matched to ERA5 reanalysis data, in conjunction with uranium-thorium dates, to produce annual palaeorainfall records. XRF analyses conducted on a Geotek Multi Sensor Core Logger (MSCL-S) produced a full geochemistry profile for the two stalagmites ranging from magnesium to uranium. The equatorial location of Gabon makes it a prime location for recording fluctuations and long-term changes in atmospheric circulation patterns, including the Intertropical Convergence Zone. Spectral analysis was used to determine any influences from atmospheric patterns or solar forcing on the stalagmite palaeorainfall record. This study provides a proof-of-concept that Gabonese stalagmites accurately preserve palaeorainfall information, paving the way for future studies extending further back in time.
How to cite: Skillicorn, E., Baldini, L., Egesi, N., Ndongo, A., M’voubou, M., Rogerson, M., Agbebia, M., Retonda-Kondja, S., Kwankam, F., Bisse, S., Okon, E., Odelugo, L., Ait Brahim, Y., Ekoko, E., Akinlabi, E., Shone, R., Taylor, G., Ilesanmi, F., and Baldini, J.: Palaeoclimate Reconstruction of Southwestern Gabon using laminated Stalagmites, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20529, https://doi.org/10.5194/egusphere-egu26-20529, 2026.
Climate models consistently project a decrease in winter rainfall in South Africa’s Southwestern Cape (SWC) in the coming decades. However, the model spread in future precipitation projections remains large, and climate models exhibit substantial biases in simulating regional rainfall. Improving projections requires a better understanding of the physical processes governing precipitation variability and change in the SWC, as well as their representation in climate models. Here, we link large-scale zonal and meridional wind patterns to SWC precipitation and derive dynamical rainfall drivers tailored to the region of interest. Using a multilinear regression framework, we dynamically reconstruct precipitation variability on interannual to multidecadal timescales and show that zonal and meridional wind in specific regions explain approximately 40% of observed historical rainfall variability. We further show that a substantial fraction of the projected precipitation decline in CMIP6 models (around 75%), as well as a large portion of the inter-model spread in future projections, can be attributed to changes in the identified dynamical drivers. Moreover, we show that models with more realistic links between circulation and regional precipitation also exhibit smaller rainfall biases. Finally, we assess the potential and limitations of applying observational constraints to SWC precipitation change and derive observation-informed precipitation projections. These projections indicate end-of-century precipitation declines exceeding the CMIP6 multi-model median, suggesting that future winter rainfall declines in the SWC may be underestimated by unconstrained model projections.
How to cite: Friedel, M., Kretschmer, M., and Hewitson, B.: Drivers of drought in Cape Town: Explaining past and future regional precipitation changes through large-scale dynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6867, https://doi.org/10.5194/egusphere-egu26-6867, 2026.
Vegetation change in the Sahel has long been framed through competing narratives on desertification and greening, but existing literature often overlooks sub-annual patterns. Therefore, this research investigates the timing, duration and magnitude of vegetation growth in the West African Sahel, which is important for climate-sensitive livelihood practices such as pastoralism and semi-permanent agriculture. Our research shows that studying the range between the seasonal maximum and minimum vegetation conditions (further defined as ‘seasonal envelope’) is more informative than looking at the annual means: it reveals which part of the seasonal cycle is changing and why that matters functionally. Additionally, linear regression modelling indicates that, while climate variables explain most of the seasonal variability, consistent prediction errors at the driest and hottest extremes point to non-linear vegetation responses.
Existing studies often assess vegetation dynamics using long-term satellite-derived Normalized Difference Vegetation Index (NDVI) records. Following this approach, our study uses combined Landsat and MODIS datasets to examine vegetation dynamics over the last 45 years at 500 x 500m resolution. Rather than focusing on annual-average trends, wet-season peak productivity and dry-season minimum conditions are analysed as seasonal indicators that directly guide land use, resource access, and mobility decision of local inhabitants, including pastoralists and agriculturalists in Ghana, Mali and Nigeria.
Over recent decades, dry-season NDVI minima have remained relatively stable, while wet-season NDVI maxima have flattened or declined across large parts of the study regions. This divergence suggests a contraction of the seasonal NDVI envelope driven primarily by reduced peak productivity rather than declining baseline vegetation conditions, as often suggested in literature. Time-series decomposition of month-to-month NDVI variability, combined with analysis of long-term seasonal means and seasonal peak values reveals functional asymmetries in vegetation response over the last 45 years.
Climate variables explain most of the interannual variability and long-term trends in linear predictive NDVI models, yet systematic modelling errors at seasonal extremes indicate the influence of non-climatic factors. To distinguish where vegetation dynamics are climate-driven or not, the second part of the study moves from historical analysis to NDVI modelling using rainfall, temperature, soil moisture, and lagged NDVI as predictor. A linear regression framework is applied, not to maximise predictive accuracy, but to diagnose where standard climate-NDVI relationships succeed or fail in capturing month-to-month vegetation responses. The largest deviations are found under high near-surface temperatures and prolonged low-precipitation conditions, proving that vegetation responses in very hot, dry circumstances are not fully captured by linear climate-NDVI relationships. These nonlinear responses are particularly noticeable during the dry-season extremes.
These results establish a baseline for interpreting vegetation change that is directly relevant to land-use monitoring, early-warning systems, food security planning, and climate adaptation policy. In semi-arid regions, where livelihoods depend on narrow windows of resource availability, small shifts in wet-season productivity or dry-season duration can result in large socio-ecological consequences.
How to cite: Van Driessche, A., Nivron, O., Hussain, E., So, E., and Shuckburgh, E.: Climate-Driven or Not? Explaining Seasonal NDVI Variability in the Sahel , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15012, https://doi.org/10.5194/egusphere-egu26-15012, 2026.
The Atlantic Meridional Overturning Circulation (AMOC) is widely anticipated to weaken by the end of the 21st century, although there is considerable disparity among state-of-the-art Earth System Models (ESM) from the Coupled Model Intercomparison Project Phase 6 (CMIP6) regarding the magnitude of this weakening. Notably, the weakening of AMOC has been shown to influence future precipitation patterns over different regions, including across West Africa. Uncertainty in projections of Sahel precipitation has persisted across generations of ESM and remains a significant challenge for stakeholders. Towards the end of the 21st century, many climate models predict a dipole pattern, characterized by a drought across western Sahel and an increased rainfall across the central Sahel.
Recent work has shown that models displaying this zonal dipole pattern tend to predict a southward shift in the position of the Atlantic Intertropical Convergence Zone (ITCZ), while those that do not show this dipole tend to predict a northward shift in the Atlantic ITCZ. Furthermore, for the models that do produce this dipole, variability in the longitude where drying transitions to increased precipitation remains difficult to explain. In this study, we seek to elucidate the relationship between changes in AMOC and changes in Sahel precipitation, particularly exploring the potential influence of AMOC on the Atlantic ITCZ and its connection with zonal variability across the Sahel. We use an ensemble of CMIP6 models and statistical analysis to connect the weakening of the AMOC to structural changes in Sahel precipitation across models. Finally, we explore potential mechanisms, including changes to the subtropical high, that may connect these critical climate signals.
How to cite: Audu, E. and Dixon, R.: The Role of the Atlantic Meridional Overturning Circulation in the Projection of Sahel Precipitation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16145, https://doi.org/10.5194/egusphere-egu26-16145, 2026.
The northern margins of Congo basin rainforests are affected by a dry season, from December to March. During this season, dry-air events are observed, characterized by a marked drop in dew point temperature (Td) below 15°C, a threshold currently used to determine the intertropical discontinuity. These episodes, linked to the Harmattan winds, penetrate the forest via the Sangha interval until they reach Libreville or Brazzaville in the most extreme cases, as in 1983. Given that the detection and characterization of these events of dry air have never been addressed in the scientific literature, the question of their impact on forests arises. Therefore, this study explores methodological approaches to detect these dry-air events and provides a first climatology and interannual variability.
Two approaches have been developed to detect dry-air events (over the area 0°-8.5°N/11°-27.5°E): on the one hand, by applying a clustering algorithm (K-Means) to the diurnal cycles of Td and, on the other hand, by setting a threshold on the distribution of daily values. As in-situ observations are sparse in Central Africa, ERA5 reanalyses are used to supplement the GSOD, GHCHh and ISD databases and capture the spatiotemporal variability of dry-air events over 1970-2024.
In the first approach, days are standardized across all the stations and then separated into two clusters by the algorithm. This leads to two distinct diurnal profiles of Td : during dry-air events, the diurnal cycle shows a characteristic negative bell-shaped curve, with lower Td values, whereas on other days Td remains higher and relatively constant throughout the day. In order to take into account the bias in reanalyses, the two clusters for ERA5 are calculated for pixels/days corresponding to stations and based on their classification as dry-air or non-dry-air events in observations. The two classifications (observations and ERA5) result in a relatively similar total number of dry-air days, with a large majority of events detected jointly (Critical Success Index: 0.72).
In the second approach, daily Td values are also aggregated and standardized across all stations. A set of thresholds (0, -0.25, ... -1.5 std) is tested over the Td distribution to refine the detection of dry air events in both observations and reanalyses. Increasing the threshold leads to an inflation in the occurrence of dry-air days, particulary in the observations; however, the large majority of events are detected jointly by the observations and ERA5 (Critical Success Index>0.7 for nearly all the thresholds). Above −0.5 std, the correlation between the interannual variability in observations and ERA5 decreases (≈0.9 below this threshold and <0.81 above).
Both approaches show similar interannual variability in dry air events with years characterized by exceptionally long and extensive episodes, such as 1983, 1989, and 1997. The climatology of dry-air event frequency is characterized by a marked latitudinal gradient, in agreement with the gradient observed in Td. The northern limit of the current forest extent lies between the 25% and 30% isofrequency contours. Beyond one-third of abnormally dry-air days during the dry season, forest gives way to savanna.
How to cite: Magnan, M., Philippon, N., and Moron, V.: Dry air episodes in the northern margins of basin Congo forests: detection and climatology , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18414, https://doi.org/10.5194/egusphere-egu26-18414, 2026.
Weak or delayed onsets to summer rains in southern Africa are becoming a growing risk. For example, the 2024 wet season start was late across countries in the region including South Africa, Zambia, and Malawi. This followed the El-Nino related drought across the region during the 2023/2024 season, illustrating risks of successive planting season challenges. Climate model ensembles project increased risk of early season drying through the coming decades.
In this contribution we explore the link between delayed southern African monsoon onset and decline in tropical-extratropical cloud bands over the more southern subtropical parts of the continent. Such declines are most profound in the regional convection-permitting for Africa (CP4-Africa) model and we interpret this within the context of CMIP model projects.
We conclude with results questioning whether these risks can be forewarned on a season-to-season basis with current S2S forecast systems. At the seasonal forecast lead-time, the answer appears to be no. However, week 2 and possibly week 3 subseasonal forecasts may have dry/wet spell skill which should be exploited in early warning systems, underpinned by more research on Rossby wave predictability.
How to cite: Hart, N., James, R., Zilli, M., Washington, R., Samuel, J., and Morris, F.: The decline in tropical-extratropical cloud bands and the delay of the southern African monsoon., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21332, https://doi.org/10.5194/egusphere-egu26-21332, 2026.
Extreme heat is an increasing concern in West Africa, particularly in the Sahel which is already exposed to high temperatures. There is growing interest from regional climate centres and national meteorological agencies in expanding capabilities to inform heat early warning systems, including enhanced seasonal forecasting.
During the Clima-Social project, part of the Weather and Climate Information Services (WISER) programme funded by the UK’s Foreign, Commonwealth and Development Office, Social Protection and Public Health stakeholders in Burkina Faso expressed interest in seasonal forecasts of extreme heat, which, unlike rainfall, are not yet produced by the National Meteorological Agency (ANAM-BF). To meet this need, the UK Met Office and the Red Cross Red Crescent Climate Centre are supporting ANAM-BF to strengthen its technical capability to deliver robust seasonal heat forecasts and advance its ambition to develop regional expertise in heat forecasting and early warning.
The Objective Seasonal Outlook Package (OSOP) is an open-source toolkit developed by the Met Office to support objective seasonal forecasting. The toolkit contains a set of Python and shell scripts that can be edited and tailored to the user's needs. OSOP generates hindcasts to evaluate model skill and probabilistic forecasts using data from Global Producing Centres, ensuring transparency and reproducibility. Using OSOP, we customised parameters to generate locally relevant, tailored seasonal forecasts from global datasets. Outputs were designed to meet ANAM-BF’s operational requirements, including specific thresholds relevant for Social Protection intervention and a sub-domain focused on Burkina Faso and surrounding regions.
The process involved technical co-development, stakeholder engagement, and prototype creation, addressing challenges in communicating forecasts. Discussions highlighted the limitations of tercile-based approaches in the context of a warming climate and the need for alternative (e.g., deciles) categories to better reflect extreme heat seasons. OSOP was tested with ANAM-BF forecasters, providing insights into practical implementation and capacity-building needs, while identifying opportunities for future development. For instance, local weather station data are currently used to bias correct simulations as well as assessing hindcast skill.
Our work demonstrates the value of co-producing new climate service capabilities that adopt an open-source access approach. This ensures stakeholders can continue to access and adapt global forecast data without relying on privately-operated systems, encouraging independent application and autonomy of services. The project offers a scalable model for seasonal heat forecasting across West Africa and beyond, with the potential for uptake by other meteorological services to supporting early action and resilience in the face of climate change.
How to cite: Harley-Nyang, D., Daron, J., Poan, E., Guigma, K., Savadogo, I., Dean, E., and Savage, N.: Building capacity for seasonal heat forecasting in West Africa: A case study with Burkina Faso’s Meteorological Agency (ANAM-BF) using the Objective Seasonal Outlook Package (OSOP) , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21592, https://doi.org/10.5194/egusphere-egu26-21592, 2026.
Posters virtual: Fri, 8 May, 14:00–18:00 | vPoster spot 4
EGU26-7064 | Posters virtual | VPS7
Late Pleistocene to Holocene Multi-proxy Paleoenvironmental and Paleoclimatic Reconstruction of the Makgadikgadi Basin, Central Kalahari, BotswanaFri, 08 May, 14:09–14:12 (CEST) vPoster spot 4
The Makgadikgadi Basin (MKB), in the central Kalahari Basin of northeastern Botswana, currently consists of a wide complex playa lake system, a relic of the Paleolake Makgadikgadi. Reconstructing the Quaternary depositional, environmental, and climatic history of the lacustrine-playa system has great significance for revealing the basin's evolution. However, its sedimentary record remains largely unexplored due to methodological challenges. In this study, four sediment cores, up to 1.6 m deep, were collected along a generally E-W transect from the western to central parts of the Ntwetwe pan, MKB. Our multi-proxy record, including sedimentology, chronology, ostracod-based biostratigraphy, and clumped (∆47) isotope geochemistry from these cores, reveals three complex hydroclimatic sequences that refine the environmental and climatic evolution of the MKB for the past 29 cal ka BP. The computed Bayesian age depth model and preliminary clumped isotope analysis on ostracod valves suggest the late Pleistocene (~29-19.5 cal ka BP) hypersaline-saline phase occurred under relatively low temperature conditions (∆47-T = ~18.5-21°C), aligning with global glacial cooling and supporting interpretations of severe aridity in the Kalahari during the Last Glacial Maximum. The shift to a freshwater ostracod assemblage by ~5.2 cal ka BP partly corresponds to the termination of the African Humid Period (AHP), with a mean temperature (∆47-T) of ~16.8°C. However, our record reveals significant complexity during the Late Holocene. The dominance of brackish water assemblage from ~4-1.6 cal ka BP suggests a prolonged transitional phase toward aridity, consistent with the broad trend of ITCZ retreat. Most notably, the late Holocene (~1.6-1 cal ka BP) assemblage, indicating a mix of brackish and freshwater taxa alongside extreme and warmer temperatures (∆47-T = ~28.5°C). This implies a period of complex hydrological variability, potentially driven by increased summer rainfall variability or episodic flood inflow. Consequently, the Late Pleistocene and Middle Holocene data align with regional patterns, while the Late Holocene sequence particularly highlights the current extreme climate in the region, suggesting ostracod growth under extreme ephemeral playa lake conditions.
How to cite: Kahsay, T., Asrat, A., Sinha, N., Marchegiano, M., and Franchi, F.: Late Pleistocene to Holocene Multi-proxy Paleoenvironmental and Paleoclimatic Reconstruction of the Makgadikgadi Basin, Central Kalahari, Botswana, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7064, https://doi.org/10.5194/egusphere-egu26-7064, 2026.
