Reliable climate change scenarios are critical for West Africa, whose economy relies mostly on agriculture and, in this regard, multimodel ensembles are believed to provide the most robust climate change information. Toward this end, we analyze and intercompare the performance of a set of four regional climate models (RCMs) driven by two global climate models (GCMs) (for a total of 4 different GCM-RCM pairs) in simulating present day and future climate over West Africa. The results show that the individual RCM members as well as their ensemble employing the same driving fields exhibit different biases and show mixed results in terms of outperforming the GCM simulation of seasonal temperature and precipitation, indicating a substantial sensitivity of RCMs to regional and local processes. These biases are reduced and GCM simulations improved upon by averaging all four RCM simulations, suggesting that multi-model RCM ensembles based on different driving GCMs help to compensate systematic errors from both the nested and the driving models. This confirms the importance of the multi-model approach for improving robustness of climate change projections. Illustrative examples of such ensemble reveal that the western Sahel undergoes substantial drying in future climate projections mostly due to a decrease in peak monsoon rainfall.

The reaction of Er3+ with polycarboxylate ligands in a gel medium frequently leads to coordination polymers that cannot be obtained via hydrothermal methods. A new Er3+ 1,2,4,5-benzenetetracarboxylate based coordination polymer, namely, Er4(C10H2O8)3(H2O)12·12H2O, has been synthesized and its crystal structure is reported herein. It crystallizes in the space group P1̄ (no. 2) with a = 10.4005(2) Å, b = 10.6486(2) Å, c = 13.6321(3) Å, α = 105.3070(7)°, β = 93.8348(8)°, γ = 108.9345(12)°, and Z = 2. To investigate the influence of the gel medium on the observed polymorphism, the Ni2+/1,3,5-benzenetricarboxylate system was studied, and polymorphism was also observed in this case. The crystal structure of a new Ni2+-containing coordination compound, namely, the Ni3(C9H3O6)2(H2O)14·4H2O, has been synthesized and its crystal structure is also reported. It crystallizes in the space group P1̄ (no. 2) with a = 6.6892(9) Å, b = 10.7615(15) Å, c = 12.3163(16) Å, α = 98.907(16)°, β = 102.171(16)°, γ = 108.074(16)°, and Z = 2. Its thermal behavior has also been studied and an hydration/dehydration cycle similar to the one already observed in the Er3+/1,3,5-benzenetricarboxylate is described. The availability for potential industrial applications of all the reported phases is discussed.

In this study, we investigate changes in temperature and precipitation extremes over West and Central Africa (hereafter, WAF domain) as a function of global mean temperature with a focus on the implications of global warming of 1.5 • C and 2 • C according the Paris Agreement. We applied a scaling approach to capture changes in climate extremes with increase in global mean temperature in several subregions within the WAF domain: Western Sahel, Central Sahel, Eastern Sahel, Guinea Coast and Central Africa including Congo Basin.While there are several uncertainties and large ensemble spread in the projections of temperature and precipitation indices, most models show high-impact changes in climate extremes at subregional scale. At these smaller scales, temperature increases within the WAF domain are projected to be higher than the global mean temperature increase (at 1.5 • C and at 2 • C) and heat waves are expected to be more frequent and of longer duration. The most intense warming is observed over the drier regions of the Sahel, in the central Sahel and particularly in the eastern Sahel, where the precipitation and the soil moisture anomalies have the highest probability of projected increase at a global warming of 1.5 • C. Over the wetter regions of the Guinea Coast and Central Africa, models project a weak change in total precipitation and a decrease of the length of wet spells, while these two regions have the highest increase of heavy rainfall in the WAF domain at a global warming of 1.5 • C. Western Sahel is projected by 80% of the models to experience the strongest drying with a significant increase in the length of dry spells and a decrease in the standardized precipitation evapotranspiration index. This study suggests that the 'dry gets drier, wet gets wetter' paradigm is not valid within the WAF domain.