The PMIP4 simulated dryland aridity changes during the Last Interglacial

Abstract

The dryland is one of the most important land ecosystems on the planet, and its changes are closely bound up with one-third of the world’s population. Investigating dryland climate change during the Last Interglacial (LIG; ∼127 ka ago) can advance our knowledge of dryland climate behaviors in an orbitally-induced warmer-than-present scenario. Based on the multiple model outputs from the Paleoclimate Modelling Intercomparison Project Phase 4, we suggest that the dryland areas during the LIG are 37% wetter than that during the preindustrial period as measured by the aridity index (AI), and 37% of the preindustrial drylands correspondingly convert to wetter subtypes. Spatially, there are hemispheric differences with drylands wetting and contracting in the Northern Hemisphere but desiccating and expanding in the Southern Hemisphere. Further diagnosis indicates that the altered precipitation is the dominant contributor to more than 72% of the AI changes, and the precipitation change is mainly attributed to the orbitally-induced redistribution of incoming insolation and heat. The secondary factor is the relative humidity change, exaggerating the AI changes in the same direction as the precipitation does. The simulation agrees reasonably with reconstructions for most regions, except Australia and southern Africa. The simulated changes in dryland aridity and the mechanism differ from that in future warming scenarios, so we claim that the LIG as a potential analogue for a warmer future does not fully hold for the dryland climate.