Empirical reconstruction of African Humid Periods across the Quaternary

Abstract. As Earth’s largest desert, the Sahara experienced periodic humid periods in the geological past, known as African Humid Periods (AHP), which have nurtured the earliest human civilizations. Reconstructing the climatic evolution of the Sahara is therefore important not only for understanding the region's own climate history but also for addressing archaeological questions related to human evolution and migration. Traditionally, the paleoclimate of this region has been reconstructed primarily from geological records, but such reconstructions are costly to obtain and are often subject to considerable chronological uncertainty. Numerical simulations can partly compensate for these limitations but also demand substantial computational resources when reconstructing climate variability over long timescales. To address these challenges, we conducted a series of climate sensitivity experiments to quantify the contributions of different climate forcings, including Earth's orbital, atmospheric CO₂, and ice sheets, to AHP formation. Based on these experiments, we developed a physically based, empirical model that reconstructs the pacing of AHP occurrence using a few key metrics: orbital parameters, CO₂ concentration, and global sea level. We validated this framework against geologic AHP reconstructions spanning the past 800 kilo-years (ka), and further applied it to reconstruct AHP throughout the entire Quaternary. This computationally efficient framework offers a new tool for reconstructing the long-term paleoclimatic evolution of the Sahara, with the potential to refine the chronology of North African geological and archaeological records.