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Scientists from various fields have long examined the factors contributing to sustainable development in Africa. The paper investigates the topic of sustainable development focusing on a very special part of Africa, the Sahel region, which is an ecoclimatic and biogeographic region of Africa facing many challenges. Consequently, the secondary research to be presented in this paper aims to review some projects and actions taken by various organizations, like the United Nations and the African Union, that stimulate sustainable development in the Sahel region. Accordingly, it focuses on a few of those projects and actions, which, on the one hand, enable sustainable agriculture, the reduction of malnutrition and food insecurity, and water usage combined with latrine construction, and which, on the other hand, enhance natural resource management and increasing resilience to climate change. The paper concludes with some remarks regarding the efficacy of these projects and actions from the viewpoint of sustainability, and finds that even though these projects and actions are of significance, there is still a long road ahead to reach sustainable development in the Sahel region. [ABSTRACT FROM AUTHOR]

Female pastoralists exhibit great strength in the drive to make a dependable livelihood from livestock tending. This is not without challenges that are genderspecific. This paper examines the socio-economic and environmental challenges faced by women pastoralists in the Sahelian Region of Northern Nigeria. Primary data were derived from an interview of 2,290 adult female household members in 6 local government areas in Bauchi and Gombe States in Nigeria. A stepwise regression analysis determined that amongst 23 socio-economic variables, 14 were significant explanatory or predictive variables (p < 0.05) for the socioeconomic status of women, as a measure of their capacity to sustain pastoralism. The results indicate that the length of time or experience in pastoralism had the most predictive power (β = 0.31; p < 0.05), and contributed 13% (R2 = 0.13) in enhancing the socio-economic status of pastoralist women. This was followed by other socio-economic factors such as the level of formal educational attained, participation in household livestock raising, ownership of large livestock, climate change awareness, prevalence of out-of-school children within the household, availability of household transportation means, category of health care facility accessed, involvement in non-agricultural economic sectors, involvement in food crop farming, ownership of small livestock, amount of rest/sleep affordable, membership of community development groups, and age. The paper recommends support for female education in pastoral communities, access to health care in remote areas, and upgrading community development groups to cooperative or self-help groups that can provide affordable loans to assist pastoralist women in thriving better in a supposedly male-dominated profession. [ABSTRACT FROM AUTHOR]

Since the droughts of the 1970s–1980s, populations in the Sahel region have opted for a mass exodus to more humid urban or rural centers. Migrations or exoduses have accelerated in recent decades due to environmental degradation and unfavorable climatic conditions. Insufficient harvests are the main reason for migration for the majority of migrants in the Sahelian areas. Migration is a major adaptation strategy to cope with extreme climatic conditions, thus requiring quantification in the destination area. The aim of this paper is to propose a metapopulation model to approximate reality by identifying the transition from one socioeconomic vulnerability group to another, from a less favorable area to favorable area in terms of natural resources, depending on the strategies, policies, and climate variability. The model was used to analyze the dynamics of socioeconomic vulnerability to study the impact of migration on the dynamics of socioeconomic vulnerability. The developed mathematical model was analyzed. Up to 2050, simulations applied to the Tougou village in northern Burkina Faso show that migration has a positive impact on the socioeconomic vulnerability of the destination area, thereby reducing the vulnerability of the population by 10% when resources are increased by up to 30%. [ABSTRACT FROM AUTHOR]

Climate change, environmental degradation, and descent-based slavery are prevailing issues in Mauritania. The relationship between the three phenomena has rarely elicited investigation, in part due to the perception that chattel slavery is an institution of the past. Despite being the last country in the world to decree its abolition in 1981, Mauritania is alleged to have one of the highest incidences of slavery in the world today. This study explores the nexus between climate change and slavery in Mauritania. The paper seeks to elucidate how the environmental interactions of the Sahel have transformed slavery’s manifestation in this multiethnic northwest African republic for more than a millennium. The author contributes to the rich literature on slavery in Mauritania by arguing that in the twenty-first century, the nexus converges on the issue of development, and that the prevalence of slavery degrades the country’s precarious environment and contributes to its underdevelopment. [ABSTRACT FROM AUTHOR]

The paper begins with popular narratives on climate change and food insecurity in the Sahel, painting a brief history of how pastoralists and their lifestyles have been understood by external scholars dealing with the theme of natural resource commons. This leads into a deeper analysis of multiple understandings of the productive political potential of the common/s as articulated by economists, historians and academics, and an exploration of the implications of these theories for the Sahel. This includes various government policies managing the commons, ranging from open-access to ranch-based systems, and the privatisation or exploitation of the commons by capitalist actors. The paper further explores three design principles, namely, mobility, inclusion and conflict mediation, for better governance in the region, and ends with a note of caution against the green-washed pursuit of growth rates, tempered by a note of hope in the figure of the vigilant and empowered pastoralist. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Security Sciences / Güvenlik Bilimleri Dergisi is the property of Gendarmerie & Coast Guard Academy Institute of Security Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper shares findings from a detailed empirical analysis of seven development projects in Kenya that supported remote pastoral communities facing food insecurity and other difficulties linked to environmental degradation and climate change. The projects sought to address these challenges by trialing various livelihood innovations in partnership with communities. These project activities were assessed using a tailored cost–benefit analysis methodology to identify those offering the best use of scarce funds, thus informing future policy and programing for such areas. This evidence suggests that (a) the difficulties communities face are creating a desperate situation, and (b) some of the innovations trialed hold promise while others are problematic. The evidence presented includes an array of local voices that vividly convey community-level dynamics and prospects. This evidence is set in context using the literatures on human security and its wider impacts, notably migration from the Sahel. This analysis found the circumstances of pastoral communities can significantly impact neighboring regions, with ongoing instability posing a threat while smart interventions that create local opportunities offer more synergistic outcomes. The paper concludes by calling for greater recognition of the options facing such communities and their wider significance as a basis for scaled up support measures. [ABSTRACT FROM AUTHOR]

Projections of future West African monsoon (WAM) precipitation change in response to increasing greenhouse gases are uncertain, and an improved understanding of the drivers of WAM precipitation change is needed to help aid model development and better inform adaptation policies in the region. This paper addresses one of those drivers, the direct radiative effect of increased CO2 (i.e., the impact of increased CO2 in the absence of SST warming and changes in plant physiology). An atmosphere-only model is used to examine both the equilibrium response and the evolution of the change over the days following the instantaneous CO2 increase. In response to the direct radiative effect, WAM precipitation increases due to a weakening of the shallow meridional circulation over North Africa, advecting less dry air into the convective column associated with the monsoon. Changes in the shallow circulation are associated with atmospheric and surface warming patterns over North Africa. A large-scale atmospheric warming pattern, whereby North Africa warms more than the monsoon region, leads to a northward shift in the Saharan heat low. In response to increased precipitation in the Sahel, local soil moisture feedbacks play a key role in determining the low-level circulation change and the location of the intertropical discontinuity. The large-scale warming patterns over North Africa result from differing levels of constraint applied by convective quasi-equilibrium. While this constraint acts strongly in the equatorial WAM region, preventing the region from warming in response to the direct radiative effect, North Africa is not strongly constrained and is therefore able to warm. [ABSTRACT FROM AUTHOR]

How heterogenous is the impact of climate change across space and the type of agricultural production? In this paper, we investigate the relationship between climate change and variability, measured by temperature and rainfall, and agricultural production at the country and agroecological zone levels of the Sahel. We consider a crop production index and five cereals (maize, millet, sorghum, wheat and rice). Based on an original climate database and an agricultural production function estimated for the period 1961–2016, we show that average rainfall and temperature during the growing season indeed have highly heterogeneous effects on agricultural production, depending on the specific needs and stress of each cereal and the agronomic and climatic conditions of each zone. [ABSTRACT FROM AUTHOR]

Natural resource conflicts in Mali in the last decade represent an important case to visualise the interconnection between land and climate issues. The country has received significant international attention in recent years both due to the announcement of large-scale land deals and due to its perceived vulnerability to climate stress. At the same time, Malian peasant movements have formed important networks of resistance and have been leading the pilot implementation of village land commissions to recognise and manage community resources, based on a new Agricultural Land Law. This paper explores emerging trends in natural resource politics through the lens of interactions between land and climate policies and discourses. We analyse the growing use of the frame of 'climate security' to associate climate change, conflict and migration in relation to countries such as Mali, by looking into the possibilities that this frame could shift focus and blame towards conflicts between marginalised groups and further close space for bottom-up participation. As an alternative, we explore the relevance of a platform of agrarian climate justice and the possibilities and challenges of enacting some of its principles through the implementation of the village land commissions. [ABSTRACT FROM AUTHOR]

Over the Plio-Pleistocene interval a strong linkage exists between northern African climate changes and the supply of dust over the surrounding oceans and continental runoff towards the Mediterranean Sea. Both these signatures in the sedimentary record are determined by orbital cycles influencing glacial variability on the one hand and northern African monsoon intensity on the other hand. In this paper, we use the intermediate-complexity model CLIMBER-2 to simulate African climate during the Plio-Pleistocene between 3.2 and 2.3 million years ago (Ma) and compare our simulations with existing and new climate reconstructions. The CLIMBER-2 model is externally forced with atmospheric CO 2 concentrations, ice sheet topography, and orbital variations, all of which strongly influence climate during the Pliocene and Pleistocene. Our simulations indicate that the records of northern Africa climate oscillate in phase with climatic precession. For the Earth's obliquity cycle, the time lag between the 41 000-year component in insolation forcing and the climatic response increased after inception of Northern Hemisphere (NH) glaciation around 2.8 Ma. To test the outcome of our simulations, we have put emphasis on the comparison between the simulated runoff of grid boxes encompassing the Sahara desert and the Sahel region and the sedimentary records of marine sediment cores from ODP Site 659 (Atlantic Ocean) and ODP Site 967 (Mediterranean). In this study we will show for the first time an extended Ti/Al record of Site 967 down to 3.2 Ma. This record strongly correlates with runoff in the Sahara and Sahel regions, whereas correlation with the dust record of Site 659 is moderate and slightly improves after NH ice sheet inception. We investigated the transient variability of the individual and combined contributions of the Sahel and Sahara regions and found significant transient behaviour overlapping the inception of NH ice sheets (2.8 Ma) and the Plio-Pleistocene transition (2.6 Ma). Prior to 2.8 Ma, a larger contribution from the Sahara region is required to explain the variability of Mediterranean dust input. After this transition, we found that a more equal contribution of the two regions is required, representing an increased influence of Sahel runoff and wet periods. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of changing weather patterns on human fertility in Chad. There is literature on the effect of mortality inducing extreme weather events and fertility. However, there is less literature on the effects of less extreme changing weather patterns on fertility. We adapt Becker’s model of demand for children to a rural Chadian context and test the model with Chadian data and explore whether any effect is through biological or agricultural mechanisms. Using GIS-coded fertility and weather data, we look for correlations between the birth rate and the number of monthly high temperature days, while partitioning data by climatic zone and staple crop intensity. Running the same models with sorghum yield as the dependent variable, we find a pattern that the same planting season high temperature days that have a negative effect on the birth rate, also have a negative effect on sorghum yields, especially in the Sahel region. This accords with our model and provides tentative evidence of an agricultural mechanism by which heat affects fertility. [ABSTRACT FROM AUTHOR]

• Comprehensive remote sensing survey of the monumental funerary landscapes of SE Mauritania. • Characterisation of three newly documented prehistoric tumulus fields. • A size-based classification system for simple stone tumuli in the Sahara is presented. • First application of Gini coefficients to the study of prehistoric funerary landscapes. • Discussion of socio-economic dynamics in the pre-Islamic Sahara-Sahel ecotone. The archaeological record of southeastern Mauritania has considerable potential to contribute to longstanding anthropological debates in world prehistory, such as early cereal domestication or the emergence and organization of complex societies, although research remains limited. The archaeological study of funerary rites offers invaluable insights into cultural attitudes towards the dead and the socio-economic dynamics of the living. The materiality of remembrance is a political statement, rooted on the ability of different social agents to mobilize labor pools and networks of obligations within a given cultural framework. As such, understanding the spatial distribution and size variability in burial monuments within funerary landscapes provides insights into the social energetics of ancestor memorialization. To that end, this paper first presents a size-based classification system for pre-Islamic conical tumulus cairns in the highlands of southeastern Mauritania, West Africa, that has much wider applicability within prehistoric Saharan archaeology. Through the first application of Gini coefficients to the study of funerary landscapes, the paper then analyses the spatial distribution and degree of monument size variability within large, spatially bounded clusters ("tumulus fields") in Dhar Tichitt in order to contextualize the socio-economic dynamics of labor mobilization at three previously undocumented tumulus fields in the western Tagant Plateau. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Resources & Ecology is the property of Journal of Resources & Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In recent decades, the Sahel has witnessed a paradoxical increase in surface water despite a general precipitation decline. This phenomenon, commonly referred to as "the Sahelian paradox", is not completely understood yet. The role of cropland expansion due to the increasing food demand by a growing population has been often put forward to explain this situation for the cultivated Sahel. However, this hypothesis does not hold in pastoral areas where the same phenomenon is observed. Several other processes, such as the degradation of natural vegetation following the major droughts of the 1970s and the 1980s, the development of crusted topsoils, the intensification of the rainfall regime and the development of the drainage network, have been suggested to account for this situation. In this paper, a modeling approach is proposed to explore, quantify and rank different processes that could be at play in pastoral Sahel. The kinematic runoff and erosion model (KINEROS-2) is applied to the Agoufou watershed (245km2), in the Gourma region in Mali, which underwent a significant increase of surface runoff during the last 60 years. Two periods are simulated, the "past" case (1960-1975) preceding the Sahelian drought and the "present" case (2000-2015). Surface hydrology and land cover characteristics for these two periods are derived by the analysis of aerial photographs, available in 1956, and high-resolution remote sensing images in 2011. The major changes identified are (1) a partial crusting of isolated dunes, (2) an increase of drainage network density, (3) a marked decrease in vegetation with the nonrecovery of tiger bush and vegetation growing on shallow sandy soils, and (4) important changes in soil properties with the apparition of impervious soils instead of shallow sandy soil. The KINEROS-2 model was parameterized to simulate these changes in combination or independently. The results obtained by this model display a significant increase in annual discharge between the "past" and the "present" case (p value<0.001), which is consistent with observations, despite a slight overestimation of the past discharge. Mean annual discharges are estimated at 0.5 ×106m³ (2. mmyr-1) and 3.29×106m³ (13.4mmyr-1) for past and present, respectively. Changes in soil properties and vegetation cover (tiger bush thickets and grassland on shallow sandy soil) are found to be the main factors causing this increase of simulated runoff, with the drainage network development contributing to a lesser extent but with a positive feedback. These results shed a new light on the Sahelian paradox phenomenon in the absence of land use change and call for further tests in other areas and/or with other models. The synergetic processes highlighted here could play a role in other Sahelian watersheds where runoff increase has been also observed. [ABSTRACT FROM AUTHOR]

The research aims to explore the complex and interrelated connections of climate change, conflict and migration in the Sahel region. Furthermore, it explores the patterns of human mobility, both internal displacement and cross-border migration, driven by climate-related environmental stressors, food insecurity, and conflict-induced displacement. The Sahel region of Africa stands at the crossroads of intersecting environmental stressors and human mobility, with climate change acting as a catalyst for conflict and migration. Using an interdisciplinary approach, this research synthesizes existing literature and incorporates quantitative analysis, qualitative insights, and geospatial mapping. It highlights case studies to explore the complex relationships between climate change, conflict, and migration in the Sahel. The study identified notable patterns in which environmental stressors, such as droughts, are closely associated with a rise in violence and displacement. The results explain how these stressors increase rivalry for limited resources, therefore intensifying disputes and stimulating migration. To address the challenges the region is facing, implement sustainable resource management and diversified economic opportunities, alongside robust governance to manage conflicts and promote social unity. Enhance community resilience through infrastructure investment and advance research, analytical tools, and multi-level stakeholder engagement for comprehensive problem-solving. [ABSTRACT FROM AUTHOR]

The mid-Pliocene (approximately 3.3–3.0 Ma) was one of the past geological warm periods. Since this past warmer climate was in many respects comparable to near future warming projections, how the regional monsoonal rainfall changed during the mid-Pliocene is an important scientific and socioeconomic concern. Based on phase 2 of the Pliocene Model Intercomparison Project (PlioMIP2), this work examines the simulated changes of Sahel summer rainfall during the mid-Pliocene. The results show the considerable intermodel uncertainty of the simulated mid-Pliocene Sahel rainfall changes in the PlioMIP2 multimodel ensemble, which is due to the uncertainties of both the simulated dynamic and thermodynamic responses to this past warmer climate. In particular, we find that the intermodel spread in the simulated northern North American warming is a major source of the uncertainty of the mid-Pliocene Sahel summer rainfall changes through two processes. One is a direct dynamic process: a stronger warming over northern North America could enhance the meridional temperature gradient between the extratropical and tropical regions, inducing an interhemisphere energy imbalance of the atmosphere. This could lead to a northward shift of the intertropical convergence zone, strengthening the Western African summer monsoon (WASM) circulation and Sahel summer rainfall. Another is an indirect thermodynamic process: the strengthened WASM circulation could further induce anomalous moisture convergence over the Sahel region, increasing local atmospheric moisture at the low-level troposphere, in favor of a wetter Sahel. Our results suggest that an improved warming simulation over northern North America is essential for the hydrological cycle simulation around the Sahel in the mid-Pliocene warmer climate. Significance Statement: The Sahel summer rainfall change in a global warmer climate is a widespread scientific and socioeconomic issue because of its important impacts on regional agriculture, ecosystems, food security, water resources, and even cultural environment. However, the present study identifies a nonnegligible intermodel uncertainty of the simulated Sahel rainfall changes during the mid-Pliocene (one of the most recent geological warm periods in Earth's history) in the Pliocene Model Intercomparison Project phase 2 (PlioMIP2) multimodel ensemble. In particular, such an intermodel uncertainty of the simulated Sahel rainfall changes during the mid-Pliocene is attributed to that of the simulated northern North America warming via both the direct dynamic process and the indirect thermodynamic process. This is quite different from the uncertainty source of near-future projections of Sahel summer rainfall changes. The present results improve our understanding of the underlying physics of the hydrological cycle change around the Sahel region in the mid-Pliocene warmer climate, with implications for the future projections of regional monsoonal rainfall. [ABSTRACT FROM AUTHOR]

The Sahel has been the object of intensive international research since the drought of the early 1970s. A considerable part of the research has focused on environmental change in general and land degradation, land cover change and climate change in particular. Rich and diverse insights from many different scientific disciplines about these three domains have been put forward. One intriguing feature is that an agreement on the overall trends of environmental change does not appear to emerge: questions such as whether the Sahel is greening, cropland is encroaching on rangelands, drought persists remain contested in the scientific literature, and arguments are supported by contrasting empirical evidence. The paper explores the generic reasons behind this situation in a systematic manner. We distinguish between divergences in interpretations emerging from (1) conceptualizations, definitions and choice of indicators, (2) biases, for example, related to selection of study sites, methodological choices, measurement accuracy, perceptions among interlocutors, and selection of temporal and spatial scales of analysis. The analysis of the root causes for different interpretations suggests that differences in findings could often be considered as complementary insights rather than mutually exclusive. This will have implications for the ways in which scientific results can be expected to support regional environmental policies and contribute to knowledge production. [ABSTRACT FROM AUTHOR]

Copyright of International Forestry Review is the property of Commonwealth Forestry Association and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the early twenty-first century, an increasing number of Muslims in the West African state of Mali turned to religious rituals in an effort to stop the desertification of the Sahel and return to the temperate climate of the past. In order better to understand the relationship between Islam and climate change, this paper uses ethnographic research to account for the perspectives and religious interpretations that civilians in southwestern Mali had for West Africa's drying climate. It shows that Muslims in Mali commonly accounted for climate change in terms of social and political conflicts. The ritual practices that Muslims used in their everyday lives to manage peacefully the negative consequences of their increasingly arid environment are particularly striking as an example of how nature serves as an obvious symbol of the quest for an end to forms of suffering related to desertification in Mali. [ABSTRACT FROM AUTHOR]

Stratospheric Aerosol Geoengineering (SAG) is proposed to offset global warming; however, the use of this approach can an impact on the hydrological cycle. We used simulations from Coupled Model Intercomparison Project (CMIP5) and Geoengineering Model Intercomparison Project (G3 simulation) to analyze the impacts of SAG on precipitation (P) and to determine its responsible causes in West Africa and Sahel region. CMIP5 historical data were first validated, the results obtained are consistent with observational data. Under the Representative Concentration Pathway scenario RCP4.5, a slight increase is found in the West Africa Region relative to present‐day climate. The dynamic processes especially, the monsoon shifts are responsible for this precipitation change. Under RCP4.5, during the monsoon period, reductions in P are 0.86%, 0.80% relative to the present‐day climate in the Northern and Southern Sahel, respectively, while precipitation is increased by 1.04% in the West African Region. Under SAG, we find a 3.71% decrease of precipitation in the West African Region while the precipitation decrease is 17.4% and 8.47% respectively in the North Sahel and South Sahel. This decrease in monsoon precipitation is mainly explained by changes in dynamics, which lead to weakened monsoon circulation and a shift in the distribution of monsoon precipitation. This result suggests that SAG deployment to balance all warming can be harmful to rainfall in WAR if the amount of SO2 to be injected into this tropical area is not taken into consideration. Plain Language Summary: Stratospheric Aerosol Geoengineering (SAG) deployment has been proposed to reduce temperature increase in the context of global warming but its impacts on the hydrological cycle and the underlying causes need to be evaluated on the regional scale. While some effects of Stratospheric Aerosol Geoengineering on the water cycle are uncertain, various studies suggest that there could be considerable changes in regional rainfall. Climate simulations (Coupled Model Intercomparison Project: CMIP5 and Geoengineering Model Intercomparison Project: GeoMIP) are used in this work to quantify the impacts on the monsoon rainfall in West Africa. We determine the changes in precipitation and the mechanisms responsible for these changes in West Africa during summer using Stratospheric Aerosol Geoengineering. Under global warming, while a slight decrease of precipitation is noted in the Sahel region, a significant decrease in rainfall is obtained over the West Africa region and the Sahel region under SAG. The main processes responsible for the changes of precipitation under SAG are determined based on the decomposition approach. Results show that changes in precipitation are largely related to changes in dynamic processes (monsoon circulation). Key Points: We determine the changes of West African Summer Monsoon precipitation using stratospheric aerosol geoengineering injections climate modelsIncrease of precipitation is presented under global warming while its decrease is obtained with stratospheric aerosol geoengineering modelsThese changes of West African Summer Monsoon precipitation are mainly driven by the dynamic processes [ABSTRACT FROM AUTHOR]

This study analyzes the potential response of the seasonal cycle of heatwaves (HWDI) and dry (CDD) and wet (CWD) spell indices over West Africa for the near- (2031–2060) and the far-future periods (2071–2100) under RCP4.5 and RCP8.5 scenarios using Coordinated Regional Climate Downscaling Experiment (CORDEX) simulations. Despite the fact that some relative biases (an underestimation of 30% for CDD, an overestimation of about 60% for CWD, and an overestimation of about 50% for HWDI) exist, during the historical period (1976–2005) in general, the CORDEX simulations and their ensemble mean outperform the seasonal variability in the above-mentioned indices over three defined subregions of West Africa (i.e., the Gulf of Guinea and Western and Eastern Sahel). They show high correlation coefficients (0.9 in general) and less RMSE. They project an increase (about 10 and 20 days) in heatwave days for both the near- and far-future periods over the whole West African region under both RCP scenarios. In addition, projections indicate that the Sahel regions will experience a decrease (about 5 days) in wet spell days from March to November, while in the Gulf of Guinea, a decrease (about 3 days) is projected throughout the year, except in the CCCLM simulation, which indicates an increase (about 5 days) during the retreat phase of the monsoon (October to December). Our results also highlight an increase (about 80%) in dry spells over the Sahel regions that are more pronounced during the March–November period, while over the Gulf of Guinea, an increase (about 40%) is projected over the entire year. Moreover, the months of increasing dry spells and decreasing wet spells coincide, suggesting that countries in these regions could be simultaneously exposed to dry seasons associated with a high risk of drought and heatwaves under future climate conditions. [ABSTRACT FROM AUTHOR]

In the Sahel region, seasonal predictions are crucial to alleviate the impacts of climate variability on populations' livelihoods. Agricultural planning (e.g., decisions about sowing date, fertilizer application date, and choice of crop or cultivar) is based on empirical predictive indices whose accuracy to date has not been scientifically proven. This paper attempts to statistically test whether the pattern of rainfall distribution over the May-July period contributes to predicting the real onset date and the nature (wet or dry) of the rainy season, as farmers believe. To that end, we considered historical records of daily rainfall from 51 stations spanning the period 1920-2008 and the different agro-climatic zones in Burkina Faso. We performed (1) principal component analysis to identify climatic zones, based on the patterns of intra-seasonal rainfall, (2) and linear discriminant analysis to find the best rainfall-based variables to distinguish between real and false onset dates of the rainy season, and between wet and dry seasons in each climatic zone. A total of nine climatic zones were identified in each of which, based on rainfall records from May to July, we derived linear discriminant functions to correctly predict the nature of a potential onset date of the rainy season (real or false) and that of the rainy season (dry or wet) in at least three cases out of five. These functions should contribute to alleviating the negative impacts of climate variability in the different climatic zones of Burkina Faso. [ABSTRACT FROM AUTHOR]

Agrometeorological services, as part of weather and climate services, are expected to play a key role in supporting sub-Saharan agriculture facing climate change and variability. In the Sahel, smallholder farmers relying on rainfed crop production systems are particularly vulnerable to climate change and variability because of low resilience and coping capacity. The provision of agrometeorological services is growing across Africa, but they often remain inaccessible for the majority of smallholder farmers or are not very relevant to support on-the-ground decision-making. Our work aims to demonstrate the hypothesis that agrometeorological services can effectively improve agricultural productivity and sustainability provided that appropriate mechanisms are put in place to ensure access, uptake and action. The paper illustrates the case study of Burkina Faso, where the National Meteorological Service, with the support of the World Meteorological Organization, engaged in the provision of accessible, reliable and relevant agrometeorological services for farmers. The study demonstrates that farmers, even in remote rural areas, are willing to profit from weather and climate services for strategic and tactical decisions in agricultural management because of relevant economic benefit. These benefits can be summarized as a 40% reduction in production costs and a 41% increase in income. Results also highlight environmental positive impacts such as the reduction by 50% in the use of fertilizers. Nevertheless, the study concludes that in order to scale-up weather and climate services in West Africa, a new business model released from the development projects approach should be explored. [ABSTRACT FROM AUTHOR]

Future changes in Sahel precipitation are uncertain because of large differences among projections from various models. In order to explore this uncertainty, we use a storyline approach which seeks to identify alternative plausible evolutions of Sahel precipitation and their driving factors. By analyzing projections from the CMIP6 climate models, we show that changes in North Atlantic and in Euro‐Mediterranean temperatures explain up to 60% of the central Sahel precipitation change uncertainty. We then construct several storylines of Sahel precipitation change based on future plausible changes in North Atlantic and Euro‐Mediterranean temperatures. In one storyline, an amplified warming of both the North Atlantic and the Euro‐Mediterranean areas promotes a northward shift of the West African monsoon, increasing precipitation over the central Sahel, while, in the opposite storyline, a moderate warming in both regions is associated with a small change in precipitation over the central Sahel and a decrease in precipitation over the western Sahel, at the end of the 21st century. These results indicate that Sahel precipitation uncertainty will not be substantially reduced unless the uncertainty in the future warming of the North Atlantic and the Euro‐Mediterranean areas is constrained. Plain Language Summary: Variations in the strength of the West African Monsoon (WAM) circulation have societal impacts on around 80 million people from Senegal to Chad. However, future projections of the WAM precipitation are uncertain for the end of the 21st century because of strong differences from one climate model to another. We show here that sources of uncertainty in Sahel precipitation depend on changes in North Atlantic and Euro‐Mediterranean temperature, relative to changes in global mean surface air temperature. We show that differences in how climate models simulate the future warming over the North Atlantic and Euro‐Mediterranean area explain a large proportion of the uncertainty in precipitation change over the central Sahel. We provide a method that could be helpful at selecting models for impact studies, based on their sensitivity to climate change over the North Atlantic ocean and Mediterranean Sea. Key Points: Future changes in Sahel precipitation are uncertainChanges in North Atlantic and Euro‐Mediterranean temperatures explain up to 60% of the Sahel precipitation change uncertaintyUncertainty in changes in Sahel precipitation is associated with uncertainty in the future northward shift of the Saharan heat low [ABSTRACT FROM AUTHOR]

Persistent precipitation deficits are among the most impactful consequences of global warming. Here we focus on changes in the annual number of dry days (NDD) and in the annual maximum length of dry spells due to a quadrupling of atmospheric CO2. We use atmosphere‐only simulations to decompose the projected changes into additive contributions. A fast adjustment leads to a global increase in NDD despite notable regional exceptions (e.g., South Asia and Sahel). The effect of the uniform component of the surface ocean warming is model‐dependent but shapes the regional distribution of the NDD response in each model. Finally, the ocean warming pattern also contributes to large uncertainties, likely through contrasting changes in large‐scale circulation. Our results thus highlight the complexity of the NDD response, with policy‐relevant practical implications for mitigation and adaptation strategies. Plain Language Summary: Global warming is expected to intensify the global water cycle, including the intensity and frequency of precipitation extremes. Yet, the response of the dry side of the daily precipitation distribution to increased atmospheric CO2 has received so far less attention. Here we show that this response remains highly model‐dependent across the latest generation of global climate models. Furthermore, we use atmosphere‐only simulations to isolate different drivers of the precipitation response. A fast radiative and vegetation adjustment to increased CO2 leads to an overall increase in the mean annual number of dry days (NDD) despite some regional exceptions. The effect of the ocean surface warming is highly model‐dependent, only partly due to the diversity of the simulated patterns of sea surface temperature anomalies. The regional response of NDD and of the maximum length of dry spells thus does not simply scale with global warming across the different models. Key Points: AGCM simulations are used to split the dry day response to increased CO2 into fast adjustment versus slower uniform and patterned SST effectsNone of the three components consistently dominates the global land response of dry days across the selected CMIP6 modelsThe uniform SST warming dominates the regional anomalies, which however do not scale with global warming across the multi‐model ensemble [ABSTRACT FROM AUTHOR]

The spatial extent of the Sahara (the largest nonpolar desert) has significant impacts on the livelihood of people residing in its surrounding areas. Despite the fact that climate change would foreseeably impact the location and size of the desert, its future responses (i.e., advance or retreat) are rarely explored in previous studies. Here, through the development of an ensemble Bayesian discriminant analysis approach, we use 10 of the latest high-resolution GCM (global climate model) simulations to document robust annual and seasonal responses of the Sahara Desert to twenty-first-century climate change, with the consideration of modeling uncertainties. We find northward shifts of the Sahara/Sahel and eastern expansion of the nondesert zone under both SSP2-4.5 and SSP5-8.5 scenarios, the former more pronounced in the wet season and the latter in the dry season. Countries located near the Mediterranean may thus experience higher risks of drought, while the projected retreat of the Saharan southern boundary will be beneficial to the local water availability of proximal countries. [ABSTRACT FROM AUTHOR]

Accurate estimation of vegetation Net Primary Productivity (NPP) has important theoretical and practical significance for ecological environment governance, carbon cycle research, and the rational development and utilization of natural resources. In this study, the spatial characteristics, temporal changes, and driving factors of NPP in the Conventional Lake Chad Basin (CLCB) were based on MODIS data by constructing a Carnegie Ames Stanford Approach (CASA) model and using a combination of Residual trends (RESTREND) and correlation analysis. The results showed that from 2001 to 2020, the NPP of the CLCB decreased annually (1.14 g C/m2), mainly because of overgrazing, deforestation, and large-scale irrigation. We conducted a driving factor analysis and found that the main influencing factor of the NPP of the CLCB is high-intensity human activities, including farmland reclamation and animal husbandry. Although the impact of climate change on NPP is not obvious in the short term, climate change may help recover NPP in the long term. The continued reduction in NPP has greatly increased the difficulty of regreening the Sahel; the increase in population density and rapid urbanization have led are major contributing factors to this. Our findings have important implications for the continued implementation of stringent revegetation policies. However, owing to limited data and methods, only the overall change trend of NPP was obtained, and comprehensive follow-up studies are needed. [ABSTRACT FROM AUTHOR]

During abrupt climate changes of the last glacial period paleorecords show large amplitude changes in the dust cycle. We use Earth System model simulations to evaluate processes operating across these events. Idealized Heinrich stadial‐like simulations show a southwards migration of tropical rainfall that dries the Sahel and reduces wet deposition causing a widespread enhancement of tropical dust loading. However, several discrepancies with marine core dust deposition reconstructions are evident. Simulations with a more limited freshwater forcing (0.4 Sv instead of 1.0 Sv) and weaker cooling over the North Atlantic (less than 3°C) show a switch in sign of the stadial dust deposition anomaly in several regions, improving agreement with paleorecords. The simulated dust cycle therefore displays in places a non‐linear response to abrupt change. The global‐mean stadial dust radiative forcing in the more realistic simulations is around −0.2 to −0.6 W m−2 and so could represent an amplifying feedback during these events. Plain Language Summary: Mineral dust in the atmosphere is mostly sourced from arid regions like the Sahara desert. The amount and geographical spread of this dust in the atmosphere is sensitive to environmental conditions such as drought. Paleoclimate records show that rapid cooling events centered on the North Atlantic during the last ice‐age also saw large increases in the rate of dust deposited over the ocean. Earth System models are a computational tool that can be used to understand the links between climate and the dust cycle. Using a series of such simulations we found that abrupt cooling events in the North Atlantic can lead to a massive increase in dust over the equatorial (tropical) regions. However, the model's response is in many places non‐linear, meaning that the change in dust is very sensitive to the magnitude of the climate changes occurring. This non‐linearity is mostly due to interactions between changes in the water cycle and the dust. We show that a less severe cooling produces a more realistic dust response when evaluated against paleo‐dust records. Since dust scatters incoming sunlight, increased atmospheric dust during these events may have amplified and even extended the cold phases. Key Points: Freshwater hosing forcing increases tropical dust loading in Earth System model simulations of the last glacial maximumSimulated response is non‐linear with forcing in some regions, particularly North AfricaWeaker events improve agreement with data and emitted dust produces a self‐amplifying feedback [ABSTRACT FROM AUTHOR]

Here we present hydrological and vegetation paleo-data extracted from 28 sites in West Africa from 5 ∘ S to 19 ∘ N and the past1000/PMIP4 IPSL-CM6A-LR climate model simulations covering the 850–1850 CE period to document the environmental and climatic changes that occurred during the Little Ice Age (LIA). The comparison between paleo-data and model simulations shows a clear contrast between the area spanning the Sahel and the savannah in the north, characterized by widespread drought, and the equatorial sites in the south, where humid conditions prevailed. Particular attention was paid to the Sahel, whose climatic evolution was characterized by a progressive drying trend between 1250 and 1850 CE. Three major features are highlighted: (1) the detection of two early warning signals around 1170 and 1240 CE preceding the onset of the LIA drying trend; (2) a tipping point at 1800–1850 CE characterized by a rainfall drop and an environmental degradation in the Sahel; and (3) a succession of drying events punctuating the LIA, the major one of which was dated to around 1600 CE. The climatic long-term evolution of the Sahel is associated with a gradual southward displacement of the Inter-Tropical Convergence Zone induced by the radiative cooling impacts of major volcanic eruptions that have punctuated the last millennium. [ABSTRACT FROM AUTHOR]

The overall performance of the simulated seasonal precipitation response to local terrestrial forcings, namely vegetation abundance and soil moisture, in the Sahel among the Coupled Model Intercomparison Project Phase Five (CMIP5) Earth System Models (ESMs) is systematically investigated and compared with its observational counterpart using a multivariate statistical method. The observed seasonal precipitation response is evaluated against a large ensemble of observational, reanalysis, and satellite data sets to provide quantification of uncertainties. The behaviour of models with and without a Dynamic Global Vegetation Model (DGVM) component is also explored, along with the mechanisms responsible for terrestrial feedback on rainfall. In general, the CMIP5 models can reasonably capture the seasonal evolution of Sahel precipitation and soil moisture, albeit with wet biases during the pre‐monsoon period and dry biases during the peak monsoon period. The non‐DGVM ESMs simulate comparable leaf area indices (LAIs) with observations, while DGVM‐enabled ESMs simulate too much year‐round LAI. The variance of precipitation that is attributed to oceanic forcings in CMIP5 is comparable with observations; however, the variance of precipitation that is attributed to terrestrial forcings is smaller in CMIP5 models than observed, especially for non‐DGVM ESMs. CMIP5 models, especially those without DGVMs, undervalue precipitation's observed response strength to soil moisture anomalies. In both observations and CMIP5 models, none of the atmospheric variables show significant responses to direct vegetation forcing, except for the response in transpiration. Although vegetation has minimal direct effect on the atmospheric state, it can affect the atmosphere by modifying soil moisture and transpiration rate indirectly, which helps explain the more realistic simulation of rainfall in DGVM‐enabled ESMs than non‐DGVM ESMs. Coupling of an ESM to a DGVM is critical in generating reasonable land–atmosphere feedback and examining future ecological and climatic changes over the Sahel. [ABSTRACT FROM AUTHOR]

This study investigates the spectacular geomorphological features of Jurassic (Younger) Granites in NE Nigeria by using field observations and some structural (i.e. joints) analyses. The study area is in the Sahel region of the Subsaharan of Africa as a transition zone between the Sahara Desert and Equatorial region, where many studies have focused on the loess deposits, ergs, climate change, and Saharan Desert boundary changes. Morphological features of rocks in the study area have not been widely discussed in the literature. However, inselbergs, ruwares, and pillar structures are the major landforms in this vast plain with an arid environment. Boulders, blocks, mushrooms, and corestones, tafoni, shelter caves, flared slopes, polygonal cracks, and weathering pits are minor features. Weathering products consisting of white-colored, granular quartz-bearing grus and red clayey laterite surround the granite masses. Subsurface weathering has favored the formation of major geomorphological features; however, subsequent superficial weathering leading to hydration and stripping occurred mostly under the humid climatic conditions with seasonal variation of dry and humid climatic conditions. Local paleoenvironmental – paleoclimatic conditions would have prevented excess weathering and erosion in the study area. [ABSTRACT FROM AUTHOR]

The present study utilizes three high-resolution simulations from the Regional Climate Model version 4 (RegCM4) to examine the late 21st century changes (2080–2099) in the West African Monsoon (WAM) features. A set of three Earth System Models are utilized to provide initial and lateral boundary conditions to the RegCM4 experiments. Our analysis focuses on seasonal mean changes in WAM large-scale dynamical features, along with their connections with the summer monsoon precipitation. In the historical period, the simulation ensemble means mimic reasonably well the intensity and spatial distribution of the WAM rainfall as well as the WAM circulation patterns at different scales. The future projection of the WAM climate exhibits warming over the whole West Africa leading to precipitation reduction over the Sahel region, and a slight increase over some areas of the Guinea Coast. The position of the African Easterly Jet (AEJ) is shifted southward and the African Easterly Waves (AEWs) activities are reduced, which affect in turn the WAM rainbelt characteristics in terms of position and strength. Overall the changes in simulated AEJ and AEWs contribute substantially to reduce the seasonal summer mean precipitation in West Africa by the late 21st century, with prevailing negative changes in the Savanna-Sahel region. To further explore the robustness of the relationships revealed in this paper, future studies using different high-resolution regional climate models with large ensemble are recommended. [ABSTRACT FROM AUTHOR]

Policy makers search for strategies to promote resilience and mitigate the effects of future climatic shocks. In this paper, we assess whether small regular cash transfers strengthen poor households' ability to mitigate the welfare effects of drought shocks. We analyze mechanisms through which cash transfers contribute to resilience, including savings, asset accumulation as well as income smoothing in agriculture and off-farm activities. We combine household survey data collected as part of a randomized control trial in rural Niger with satellite data used to identify exogenous rainfall shocks. The results show that cash transfers increase household consumption by about 10 percent on average. Importantly, this increase is mostly concentrated among households affected by drought shocks, for whom welfare impacts are larger than transfer amounts due to households' enhanced ability to protect earnings in agriculture and off-farm businesses when shocks occur. The results suggest that multi-year cash transfer programs can foster poor households' resilience by facilitating savings and income smoothing. [ABSTRACT FROM AUTHOR]

Africa's central Sahel region has experienced prolonged drought conditions in the past, while rainfall has recovered more recently. Global climate models project anything from no change to a strong wetting trend under unabated climate change; and they have difficulty reproducing the complex historical record. Here we show that when a period of dominant aerosol forcing is excluded, a consistent wetting response to greenhouse‐gas induced warming emerges in observed rainfall. Using the observed response coefficient estimate as a constraint, we find that Coupled Model Intercomparison Project Phase 6 climate models with a realistic past rainfall response show a smaller spread, and higher median, of projected future rainfall change, compared to the full ensemble. In particular, very small or negative rainfall trends are absent from the constrained ensemble. Our results provide further evidence for a robust Sahel rainfall increase in response to greenhouse‐gas forcing, consistent with recent observations, and including the possibility of a very strong increase. Plain Language Summary: Rainfall is a critical resource for a large population in the African Sahel region, but rainfall levels have strongly varied in the past. It is unclear what will happen in the next decades, because some climate models suggest little to no change in average rainfall, while other models project a strong increase due to climate change. Our study aims to narrow down this uncertainty. In the past, both greenhouse gases and aerosols influenced Sahel rainfall, to different degrees during different periods; and models may not capture both mechanisms equally well. However, future rainfall changes will likely be driven mainly by greenhouse gas levels. We identify models that closely match the rainfall change that was observed in a recent period with dominant greenhouse gas forcing. These models also tend to project stronger rainfall increases than other models. Indeed, their multi‐model mean projection is an increase by almost 50% by 2040; while none of them projects stable rainfall levels or even a reduction. Thus, it appears more likely now that rainfall in the Sahel will increase substantially over the next few decades. Key Points: We identify the response of Sahel rainfall to greenhouse gas‐induced global warming in the historical recordMany global climate models of the latest generation (Coupled Model Intercomparison Project Phase 6) do not reproduce the observed rainfall responseObservational constraint reduces model spread and implies stronger rainfall increase under further warming than in full ensemble [ABSTRACT FROM AUTHOR]

This study assesses changes in extremes precipitation and temperature in West Africa under a high greenhouse gas scenario, that is, a representative concentration pathway 8.5, and under a scenario of stratospheric aerosol geoengineering (SAG) deployment using the NCAR Community Earth System Model version 1. We use results from the Geoengineering Large Ensemble simulations (GLENS), where SAG is deployed to keep global surface temperatures at present day values. This impact study evaluates changes in some of the extreme climate indices recommended by the Expert Team Monitoring on Climate Change Detection and Indices. The results indicate that SAG would effectively keep surface temperatures at present day‐conditions across a range of indices compared to the control (CRTL) period, including Cold days, Cold nights and Cold Spell Duration Indicator which show no significant increase compared to the CRTL period. Regarding the extremes precipitation, GLENS shows mostly a statistically significant increase in annual precipitation and statistically significant decrease in the number of heavy and very heavy precipitation events relative to the CRTL period in some regions of Gulf of Guinea. In the Sahel, we notice a mix of statistically significant increase and decrease in Max 1‐day and Max 5‐days precipitation amount relative to the CRTL period at the end of the 21st century when large amounts of SAG has been applied. The changes in extreme precipitation indices are linked to changes in Atlantic Multidecadal Oscillation, NINO3.4 and Indian Ocean Dipole and these changes in extreme precipitation are driven by change in near surface specific humidty and atmospheric circulation. Key Points: We explore changes in extremes precipitation and temperature under a scenario of stratospheric aerosol geoengineering deploymentUse of stratospheric aerosol geoengineering in the future could lead to a climate that is close to present day in West AfricaChanges in extreme precipitation indices are linked to changes in sea surface temperature [ABSTRACT FROM AUTHOR]

Migration is often considered a form of climate change adaptation by which individuals, households, and communities seek to reduce the risks associated with climate change. In this study, we examine first-time seasonal migration out of a village in North-Western Burkina Faso to neighbouring countries, triggered by more irregular rainfall patterns. Through a set of 52 qualitative interviews, we analyse the perceptions of migrants themselves as well as the sending community regarding migration consequences. Men migrated in the off-season, whereas women stayed behind. Most migrant men and wives of migrants perceive migration to have negative consequences for their socio-economic situation and their health. Despite this, a lack of options and deteriorating environmental conditions might force the men to move again. We interpreted the range of narratives provided by women and men against the background of the scientific literature on migration as climate change adaptation. While migration could be beneficial, this study challenges the notion of migration as an effective adaptation strategy for people in climate-vulnerable settings, who lack other options. [ABSTRACT FROM AUTHOR]

The Sahel is a dust source region where dust emission could be drastically modified in the future due to climatic and land use changes. Based on observations of meteorological parameters and dust concentration for about 1,000 rain events, we investigated the processes leading to dust emission during the rainy season when Mesoscale Convective Systems (MCSs) regularly cross the Sahel. We show that the highest wind speed is strongly linked to the MCS cold pool intensity, which is characterized by a drop in surface temperature. This is observed during the premonsoon period (∼May to June) when the midtroposphere is still sufficiently dry to allow intense evaporation of raindrops. Because this coincides with the time of the year that the surface is the least protected by the vegetative residue, the premonsoon wind speed leads to the highest observed dust concentration in our record. Most of the highest wind speed occur before or just at the beginning of a rainy event allowing a large part of the dust raised to be transported ahead the rain limiting dust removal by wet scavenging. Finally, we show that the number of 5‐min dust concentration higher than 5,000 μg m−3 is almost only occurring during the rainy season. These results suggest that until the dust models fail to correctly resolve MCS, it will be difficulty to obtain reliable estimates of dust emission from the Sahel for the present or future scenarios. Key Points: During the Sahelian rainy season, the intensity of the strongest wind speed is linked to the intensity of the cold poolsMost of the strongest wind speed occur just before or just after a rain event starts leading to efficient and intense dust emissionThe highest dust concentration is recorded during May‐June when the wind speed is the strongest and the vegetation cover is the lowest [ABSTRACT FROM AUTHOR]

In this study, the performance of sixteen Coupled Model Intercomparison Project Phase 6 (CMIP6) models in simulating extreme precipitation indices over West Africa has been evaluated. Nine extreme precipitation indices defined by the Expert Team on Climate Change Detection and Indices (ETCCDI) have been used. The performance of CMIP6 models and their ensemble mean was examined by comparing the model results to that of Global Precipitation Climatology Project One-Degree Daily Dataset (GPCP) and Tropical Rainfall Measuring Mission Multi-satellite Precipitation Analysis 3B42 (TRMM) gridded observations during the present-day period 1997–2014 with focus on the summer months (i.e., June–July–August, JJA). Our results show that CMIP6 models reasonably reproduce the spatial patterns of the extreme precipitation indices over the entire region, although their performance is quite different between Sahel and Guinea coast subregions. The gridded observations exhibit significant differences in their estimates of the indices evaluated, and the CMIP6 models are generally closer to GPCP than to TRMM. The models broadly exhibit too many consecutive wet days (CWD) resulting in widespread overestimation over entire West Africa. Also, the heavy (R10 mm) and very heavy (R20 mm) precipitation days are considerably overestimated especially over the mountain regions. Overall, the ensemble mean outperforms any individual model at capturing mean distributions of the extreme precipitation indices, particularly in comparison to the two gridded observations. [ABSTRACT FROM AUTHOR]

This study analyses the long‐term (1950–2100) observed and projected changes in springtime (March–May) heat waves (HWs) in West Africa under climate change. To that end, 28 climate models participating to the fifth Coupled Model Intercomparison Project (CMIP5) are considered, after a statistical post‐correction of their biases. A multi‐scale approach is proposed, covering the Sahel, Senegal, and three thermally‐coherent zones within Senegal. HWs are defined as a sequence of at least three consecutive days above a moving 95th percentile of current temperature distributions. Climate change over Senegal translates into a general shift of the whole statistical distribution towards higher temperature values, with a general stability in the shape of the distribution. Ongoing mean warming could reach +5°C in 2100 under RCP8.5 scenario, implying that coastal Senegal could experience then a mean climate comparable to the hinterland parts today. HWs have increased in intensity, frequency and duration across Sahel and Senegal over the past years, such intensification being higher on recent decades. Future HWs over all regions present intrinsic properties that radically differ from those observed so far. The severity and length of HWs displayed stationary conditions until the late 1990s, but started increasing since then. Projected changes show marked and rapid increase in these variables, the amplitude of which is primarily RCP‐dependent, and secondarily region‐dependent. For both metrics, the largest changes occur over hinterland Senegal and Sahel. There, under RCP8.5 and after the 2070s, the whole spring season could be considered as a permanent HW lasting 3 months. Along the coast, by contrast, average temperatures are both weaker and more variable, causing more frequent threshold crossings and limiting the duration of HWs. The multi‐scale approach used here highlights contrast within Senegal, which constitutes important information for public policy decision‐makers and its inhabitants in terms of adaptation to climate change. [ABSTRACT FROM AUTHOR]

The northwest African country of Mauritania is a vast, desert territory, which was historically been dominated by pastoral nomads. Since independence in 1960, the country has witnessed a dramatic sedentarization of its nomadic population, as well as settlements in and movements to urban centers. This vast sedentarization movement coupled with internal and interregional migration has resulted in the growth of Mauritania's urban population from less than 10 percent of the total population in 1965 to nearly 90 percent in 2013. Factors that have caused this rapid urbanization, include the droughts that spanned the late 1960s through to the early 1980s, and the turbulent transformation of Mauritania's political economy. The aim of this study is to determine and examine internal migration flows to analyze the relationship between long-term rainfall changes and dynamic spatial demographic shifts in terms of movements toward urban centers. In this regard, we propose an assessment approach that integrates official statistics from the decennial census and rainfall data, with available socioeconomic variables, to characterize interregional migration flows. Our result confirms that rates of interregional migration remain elevated and are expected to increase. In 2013, 702,575 individuals were documented as having participated in interregional migration, comprising 17.5 percent of the total population. In comparison, there were 477,814 individuals, which migrated inter-regionally in 2000, and 208,039 in 1988. These results demonstrate distinct interactions between climate variability and interregional migration in Mauritania throughout the past four decades. [ABSTRACT FROM AUTHOR]

The summertime Sahara and Sahel are the world's largest source of airborne mineral dust. Cold-pool outflows from moist convection ('haboobs') are a dominant source of summertime uplift but are essentially missing in global models, raising major questions on the reliability of climate projections of dust and dust impacts. Here we use convection-permitting simulations of pan-African climate change, which explicitly capture haboobs, to investigate whether this key limitation of global models affects projections. We show that explicit convection is key to capturing the observed summertime maximum of dust-generating winds, which is missed with parameterised convection. Despite this, future climate changes in dust-generating winds are more sensitive to the effects of explicit convection on the wider meteorology than they are to the haboobs themselves, with model differences in the change in dust-generating winds reaching 60% of current values. The results therefore show the importance of improving convection in climate models for dust projections. [ABSTRACT FROM AUTHOR]

Drought is a natural hazard that has affected agriculture which is the main livelihood of the people in the Sahel region of Nigeria (SRN) in the last few decades. Continental and regional drought monitoring is very essential for the development of an early warning system especially in the context of global warming. The severity of drought was simulated to evaluate climate change impacts on drought conditions in the SRN using the standardized precipitation evapotranspiration index (SPEI), the standardized precipitation index (SPI), the original and self-calibrated Palmer drought severity indices (PDSI and scPDSI). The difference between the Hargreaves (Har) and Penman-Monteith (PM) potential evapotranspiration (PET) models used for the computation of the SPEI were also studied. The Mann-Kendall test was used to analyze the trends and significance of the climatic data. The time series of four drought indices were compared at six synoptic stations within the SRN. The influences of climate change on drought conditions were examined with a hypothetical gradual precipitation changes (+ 10%) and 2 °C increase in temperature. The findings showed that there was a significant correlation between Har and PM models, and between the SPEIs estimated from the two PET models. However, a major drought episode (1982–1983) indicated by SPEI-PM was not captured under SPEI-Har. Considering climate change conditions, the severity and intensity of drought increases as the twenty-first century progresses under both the scPDSI and SPEI mainly due to more demand for moisture based on a temperature rise of 2 °C. Either a slight (10%) increase or decrease in the monthly accumulation of rainfall depth will not have a significant impact on drought, if there is a slight increase in temperature as it is being currently observed in the SRN. Thus, it is pertinent for stakeholders to critically consider establishing policies that can ameliorate this phenomenon as the twenty-first century progresses. [ABSTRACT FROM AUTHOR]

Decadal climate prediction has been one of the most popular topics in recent climate change studies. It is closely linked to our daily life, deeply affecting the wellbeing of people and global economic growth. Among those climate variables, precipitation is essential for industrial and agricultural productions but it's also hard to precisely predict. In this study, we provide observational evidence for the relationship of mean precipitation in the Northern Hemisphere (NH), NH tropics and Sahel with the five Atlantic Meridional Overturning Circulation (AMOC) indicators on the multidecadal time scale. We conclude that precipitation in those three regions exhibits a consistent multidecadal variability from 1901 to 2015. The correlations between NH precipitation and AMOC indicators are strong and significant. The NAO-based AMOC indicator leads the precipitation by 8 years and the correlation coefficient reaches 0.9 higher than other oceanic indicators. It is the NAO that forces the AMOC transporting heat to the North Atlantic and induces sea surface temperature (SST) dipole which eventually affects the multidecadal precipitation change in NH. As the AMOC_NAO indicator leads the precipitation, we employ it as a predictor and construct a linear model to make a future prediction based on historical data. It indicates that the precipitation will decrease in the following few years, and then will rise again. [ABSTRACT FROM AUTHOR]

The main focus of this study is the zonal contrast of the Sahel precipitation shown in the CMIP5 climate projections: precipitation decreases over the western Sahel (i.e., Senegal and western Mali) and increases over the central Sahel (i.e., eastern Mali, Burkina Faso and Niger). This zonal contrast in future precipitation change is a robust model response to climate change but suffers from a lack of an explanation. To this aim, we study the impact of current and future climate change on Sahel precipitation by using the Large Ensemble of the Community Earth System Model version 1 (CESM1). In CESM1, global warming leads to a strengthening of the zonal contrast, as shown by the difference between the 2060–2099 period (under a high emission scenario) and the 1960–1999 period (under the historical forcing). The zonal contrast is associated with dynamic shifts in the atmospheric circulation. We show that, in absence of a forced response, that is, when only accounting for internal climate variability, the zonal contrast is associated with the Pacific and the tropical Atlantic oceans variability. However, future patterns in sea surface temperature (SST) anomalies are not necessary to explaining the projected strengthening of the zonal contrast. The mechanisms underlying the simulated changes are elucidated by analysing a set of CMIP5 idealised simulations. We show the increase in precipitation over the central Sahel to be mostly associated with the surface warming over northern Africa, which favour the displacement of the monsoon cell northwards. Over the western Sahel, the decrease in Sahel precipitation is associated with a southward shift of the monsoon circulation, and is mostly due to the warming of the SST. These two mechanisms allow explaining the zonal contrast in precipitation change. [ABSTRACT FROM AUTHOR]

Spring migration phenology is shifting towards earlier dates as a response to climate change in many bird species. However, the patterns of change might not be the same for all species, populations, sex and age classes. In particular, patterns of change could differ between species with different ecology. We analyzed 18 years of standardized bird capture data at a spring stopover site on the island of Ponza, Italy, to determine species-specific rates of phenological change for 30 species following the crossing of the Mediterranean Sea. The advancement of spring passage was more pronounced in species wintering in Northern Africa (i.e. short-distance migrants) and in the Sahel zone. Only males from species wintering further South in the forests of central Africa advanced their passage, with no effect on the overall peak date of passage of the species. The migration window on Ponza broadened in many species, suggesting that early migrants within a species are advancing their migration more than late migrants. These data suggest that the cues available to the birds to adjust departure might be changing at different rates depending on wintering location and habitat, or that early migrants of different species might be responding differently to changing conditions along the route. However, more data on departure time from the wintering areas are required to understand the mechanisms underlying such phenological changes. [ABSTRACT FROM AUTHOR]

The impact of climate change on Sahel precipitation suffers from large uncertainties and is strongly model-dependent. In this study, we analyse sources of inter-model spread in Sahel precipitation change by decomposing precipitation into its dynamic and thermodynamic terms, using a large set of climate model simulations. Results highlight that model uncertainty is mostly related to the response of the atmospheric circulation to climate change (dynamic changes), while thermodynamic changes are less uncertain among climate models. Uncertainties arise mainly because the models simulate different shifts in atmospheric circulation over West Africa in a warmer climate. We linked the changes in atmospheric circulation to the changes in Sea Surface Temperature, emphasising that the Northern hemispheric temperature gradient is primary to explain uncertainties in Sahel precipitation change. Sources of Sahel precipitation uncertainties are shown to be the same in the new generation of climate models (CMIP6) as in the previous generation of models (CMIP5). [ABSTRACT FROM AUTHOR]

We analyze projected changes in climate extremes (extreme temperatures and heavy precipitation) in the multimodel ensembles of the fifth and sixth Coupled Model Intercomparison Projects (CMIP5 and CMIP6). The results reveal close similarity between both ensembles in the regional climate sensitivity of the projected multimodel mean changes in climate extremes, that is, their projected changes as a function of global warming. This stands in contrast to widely reported divergences in global (transient and equilibrium) climate sensitivity in the two multimodel ensembles. Some exceptions include higher warming in the South America monsoon region, lower warming in Southern Asia and Central Africa, and higher increases in heavy precipitation in Western Africa and the Sahel region in the CMIP6 ensemble. The multimodel spread in regional climate sensitivity is found to be large in both ensembles. In particular, it contributes more to intermodel spread in projected regional climate extremes compared with the intermodel spread in global climate sensitivity in CMIP6. Our results highlight the need to consider regional climate sensitivity as a distinct feature of Earth system models and a key determinant of projected regional impacts, which is largely independent of the models' response in global climate sensitivity. Plain Language Summary: Many articles analyze and compare global climate sensitivity in climate models, that is, how their global warming differs at a given level of CO2 concentrations. However, global warming is only one quantity affecting impacts. To assess human‐ and ecosystem‐relevant impacts, it is essential to evaluate the regional climate sensitivity of climate models, that is, how their regional climate features differ at a given level of global warming. We analyze here regional climate sensitivity in the new multimodel ensemble that will underlie the conclusions of the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). This ensemble of model projections is called the "Sixth Coupled Model Intercomparison Project" or CMIP6. We find that differences in regional climate sensitivity between models in CMIP6 often contribute more to the uncertainty of regional extremes projections than the uncertainty in global mean warming between models. Overall, the regional climate sensitivity features in the CMIP6 models' projections ensemble are very similar to those of the prior ensemble (CMIP5), although the model ensembles have been highlighted to differ in their global climate sensitivity over the 21st century. Key Points: Changes in climate extremes as a function of global warming are quasilinear and determine a "regional climate sensitivity" in CMIP5 and CMIP6The regional climate sensitivity of climate extremes is found to be very similar in CMIP5 and CMIP6, unlike global climate sensitivityModel spread in regional climate sensitivity in CMIP6 contributes more to uncertainty of projected extremes than global climate sensitivity [ABSTRACT FROM AUTHOR]

Extreme rainfall is expected to increase under climate change, carrying potential socioeconomic risks. However, the magnitude of increase is uncertain. Over recent decades, extreme storms over the West African Sahel have increased in frequency, with increased vertical wind shear shown to be a cause. Drier midlevels, stronger cold pools, and increased storm organization have also been observed. Global models do not capture the potential effects of lower- to midtropospheric wind shear or cold pools on storm organization since they parameterize convection. Here we use the first convection-permitting simulations of African climate change to understand how changes in thermodynamics and storm dynamics affect future extreme Sahelian rainfall. The model, which simulates warming associated with representative concentration pathway 8.5 (RCP8.5) until the end of the twenty-first century, projects a 28% increase of the extreme rain rate of MCSs. The Sahel moisture change on average follows Clausius–Clapeyron scaling, but has regional heterogeneity. Rain rates scale with the product of time-of-storm total column water (TCW) and in-storm vertical velocity. Additionally, prestorm wind shear and convective available potential energy both modulate in-storm vertical velocity. Although wind shear affects cloud-top temperatures within our model, it has no direct correlation with precipitation rates. In our model, projected future increase in TCW is the primary explanation for increased rain rates. Finally, although colder cold pools are modeled in the future climate, we see no significant change in near-surface winds, highlighting avenues for future research on convection-permitting modeling of storm dynamics. [ABSTRACT FROM AUTHOR]