Reconciling the discrepancy of post-volcanic cooling estimated from tree-ring reconstructions and model simulations over the tibetan plateau

Abstract

Volcanic eruptions are a major factor influencing global climate variability/ usually with a cooling effect. The magnitudes of post-volcanic cooling from historical eruptions estimated by tree-ring reconstructions differ considerably with the current climate model simulations. It remains controversial on what is behind such a discrepancy. This study investigates the role of internal climate variability (i.e., El Nino/Southern Oscillation (ENSO) warm phase) with a regional focus on the Tibetan Plateau (TP), using tree-ring density records and long historical climate simulations from the fifth Coupled Model Intercomparsion Project (CMIP5). We found that El Nino plays an important role behind the inconsistencies between model simulations and reconstructions. Without associated El Nino events, model simulations agree well with tree-ring records. Divergence appears when large tropical eruptions are followed by an El Nino event. Model simulations, on average, tenci to overestimate post-volcanic cooling during those periods as the occurrence of El Nino is random as part of internal climate variability.