The RegCM3 has been integrated for the period of 1960–2002 using initial and lateral boundary conditions from the NCEP re‐analyses at 6‐hour intervals. Greenhouse gas concentrations remain fixed and the land‐use/soil properties are not altered. The RegCM3 accurately portrays a trend from wetter conditions in the 1960s to very dry conditions in the 1980s. The dry 1980s temperatures in the Sahel are approximately 3°K warmer than the wet 1960s, caused by a reduction in precipitation and clouds leading to an increase in the net absorbed solar radiation at the surface. This anomalous warming maintains the steepest meridional temperature gradient and therefore the African Easterly Jet in lower latitudes. The initiation of dry conditions starts in June and persists through July and August in the model simulations. The initiation of dry conditions appears to be related to a weaker Tropical Easterly Jet which may be linked to warmer Indian Ocean temperatures over the past several decades.

The accurate assessment of the potential impacts of climate change on societies and ecosystems requires regional and local‐scale climate change information. This assessment is critical for the development of local, national, and international policies to mitigate and adapt to the threat of climate change. Characterizing uncertainties in regional climate change projections (RCCPs) is therefore crucial for making informed decisions based on quantitative risk analysis. However, information about fine‐scale climate change and associated uncertainties is lacking due to the absence of a coordinating framework to improve the characterization of such uncertainties. Here we propose the inception of such a framework.

Purpose The purpose of this study is to examine the relative importance of climate normals (average long-term temperature and precipitation) in explaining net farm revenue per hectare (NRh) for supplementary irrigated and rainfed cocoa farms in Nigeria. Design/methodology/approach NRh was estimated for 280 cocoa farmers sampled across seven Nigerian states. It was regressed on climate, household socio-economic characteristics and other control variables by using a Ricardian analytical framework. Marginal calculations were used to isolate the effects of climate change (CC) on cocoa farm revenues under supplementary irrigated and rainfed conditions. Future impacts of CC were simulated using Six CORDEX regional climate model (RCM) ensemble between 2036-2065 and 2071-2100. Findings Results indicate high sensitivity of NRh to Nigerian climate normals depending on whether farms use supplementary irrigation. Average annual temperature increases and precipitation decreases are associated with NRh losses for rainfed farms and gains for supplementary irrigated cocoa farms. Projections of future CC impacts suggest a wide range of NRh outcomes on supplementary irrigated and rainfed farm revenues, demonstrating the importance of irrigation as an effective adaptation strategy in Nigeria. Originality/value This paper uses novel data sets for simulating future CC impacts on land values in Nigeria. CORDEX data constitute the most comprehensive RCMs projections available for Africa.