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Abstract The regional climate as it is now and in the future will put pressure on investments in sub-Saharan Africa in water resource management, fisheries, and other crop and livestock production systems. Changes in oceanic characteristics across the Atlantic Ocean will result in remarkable vulnerability of coastal ecology, littorals, and mangroves in the middle of the twenty-first century and beyond. In line with the countries' objectives of creating a green economy that allows reduced greenhouse gas emissions, improved resource efficiency, and prevention of biodiversity loss, we identify the most pressing needs for adaptation and the best adaptation choices that are also clean and affordable. According to empirical data from the field and customized model simulation designs, the cost of these adaptation measures will likely decrease and benefit sustainable green growth in agriculture, water resource management, and coastal ecosystems, as hydroclimatic hazards such as pluviometric and thermal extremes become more common in West Africa. Most of these adaptation options are local and need to be scaled up and operationalized for sustainable development. Governmental sovereign wealth funds, investments from the private sector, and funding from global climate funds can be used to operationalize these adaptation measures. Effective legislation, knowledge transfer, and pertinent collaborations are necessary for their success.

Climate services favor adopting strategies to increase agricultural productivity, enhance sustainable development, and adapt to unavoidable climate variability and change. However, for climates services to be effective, they must be accessible and suitable to user needs. This study investigated the effects of customized climate services (CCS) on land and labor productivity. Portraying the case of CCS delivered in the districts of Bolgatanga (Northern Ghana), Dano and Ouahigouya (western and northern Burkina Faso) in West Africa, it used: i) historical panel data of daily rainfall, yields, agricultural input, and output prices; ii) cost statements of farm operations and iii) other survey data from beneficiaries of on-farm demonstrations (pilot sites). Different results were found across farmers on the demonstrator sites, with Dano and Bolgatanga recording the best land and labor productivity. Strong and positive effects were observed in Dano, where land productivity increased by 200% and labor productivity doubled despite consecutive pluviometric extremes such as heavy rain events and prolonged dry spells in the 2017 and 2018 cropping seasons. Further investigation showed that CCS was particularly favorable to land and labor productivity of farmers who were committed to the advisory given by the CCS providers. Therefore, as perishable goods, the success of CCS applications would require thorough co-production, delivery, and monitoring for their effectiveness in improving land and labor productivity for agriculture in semi-arid regions of West Africa.

In the field of climate services, characterization of rainfall extremes is useful to identify and quantify rain rates that can trigger floods, on-farm water stagnation, excess run-off causing arable soil depletion and other natural hazards. Delving through multiple sources of observational uncertainties, we define extreme rain events (EREs) using the 99th percentile thresholds of daily accumulated rainfall, extracted from historical data records (1960–2016) of manual and tipping bucket gauges. The results of the analysis show that the average amplitude of these threshold values has been increasing in the recent years. Meanwhile, the three categories of heavy rains exhibit an intra-seasonal timing that follows different phases of the West African monsoon. Category 1 & 2 occur mostly in the northern Sahel, between weeks 27 and 35 of the year with an accumulated daily amount varying in the 37–65 mm range and less than or equal to 85 mm/day respectively. In category 3, rain rates are greater than 85 mm/day, observed between 28th and 38th week-of-the-year predominantly in the southern and western of the Sahelsub-region. For each category of ERE, high risk areas are mapped using the relative probability of occurrence at local scale. This classification can be exploited for forecasts verification, climate model evaluations and operational early warning services against high impact rainfall events. Keywords: Observations uncertainty, Thresholds, Extreme rain event, Sahel, West Africa

Surface observations provide ground evidence of climate change to support the scientific guidance paving the way to better adaptation and mitigation actions. The West African Science Service Centre on Climate Change and Adapted Land Use (WASCAL) has designed a multi-stakeholder initiative to rescue the deteriorated near-surface weather, climate and hydrological equipment of West African countries. The main goal for this multi-stakeholder framework was to monitor the climate and collect long term and high-quality records of essential climate variables in support of research, education, capacity building, and climate services provision. Proactive and inclusive partnership initiatives were developed to jointly (re)design and (re)implement near surface observatiories with the national meteorological and hydrological services or agencies (NMHS/As) in West Africa. The co-production scheme used by this framework succeeded in evaluating the existing observations networks, to modernizing sensors and field equipment, and densifying the sites in order to improve the quality of data collection, transmission, archiving, processing and sharing policies. After more than four years of community-of-practice, the existing regional basic hydroclimatic was increased/upgraded by 45% with automatic weather observing systems while fifty automatic water level, ten water quality sensors, three mesoscale research catchments, and several pilot sites to benefit countries’ services provision, research infrastructure, education, and capacity building. Country-specific data sharing policies were harmonized and signed to support data services delivery. This practice paper exposes the concepts, outcomes, challenges, lessons learned and the ways forward in setting-up the framework and keeping it on working to leverage the co-production of data & information services for better-informed decision-making in the field of sustainable development in West Africa.