Theoretical and Empirical Reconstruction of Nigerian Climate Variability Over the Past 500 Years Using Paleoclimate Proxies and Historical Documentary Records

Extending the perspective on Nigerian climate variability beyond the 100 to 150 years of instrumental records requires integration of paleoclimate proxy data and historical documentary sources, yet a systematic multi-proxy climate reconstruction for Nigeria extending beyond the instrumental period does not exist. This study presents an original theoretical and empirical reconstruction of Nigerian climate variability over the past 500 years using a multi-proxy approach combining tree ring width records from West African Sahel species, stable oxygen isotope data from speleothems in Plateau and Kogi state caves, lake sediment grain size proxies from Lake Oguta and Lake Bakolori, and historical documentary records from colonial meteorological archives and pre-colonial Arabic chronicles. The theoretical framework for multi-proxy synthesis adapts Signal Processing and Inverse Theory methods for climate field reconstruction to the sparse and heterogeneous Nigerian proxy network. A composite climate index representing rainfall variability is reconstructed at decadal resolution from 1520 to 2022 CE, calibrated against the NiMet instrumental record for the overlap period. Results reveal previously undocumented multi-decadal drought episodes in the 1640s to 1670s and 1780s to 1810s that exceed the severity of the well-known 1970s to 1980s Sahel drought, with documented societal consequences traceable in pre-colonial historical records. The last three decades of the instrumental record emerge as among the wettest in the 500-year reconstruction for the Guinea Savanna zone. Original theoretical contributions include a Bayesian ensemble reconstruction methodology adapted to low-proxy-density tropical African conditions. Keywords: paleoclimate, proxy reconstruction, Nigeria, multi-proxy, climate history.