Intensified aridity in northern China during the middle Piacenzian warm period

Abstract

Dryland areas are predicted to expand significantly due to global climate change and such expansion would reduce carbon sequestration and enhance warming, forming a positive feedback. However, a contrasting theory is that Earth’s thermal equator will move northward in a warm climate, resulting in precipitation increase and dryland shrinking. A study of past warm periods analogous to future climate can help distinguish between these predictions. The middle Piacenzian warm period during ∼3.3–3Ma is the best pre-Quaternary analog to late 21st century climate, but Pliocene terrestrial paleoclimatic records that can resolve orbital-timescale variations are scarce. Here we present a pedogenic carbonate oxygen isotope record spanning the entire Pliocene from the Chinese Loess Plateau. The record reveals intensified evaporation-induced aridity during the warm phases of the middle Piacenzian period. These records provide the first evidence demonstrating that intensified evaporation in northern China counteracted any precipitation increase associated with thermal equator migration during the warm periods. These results suggest that Asian drylands will likely expand with future warming, requiring a revision of model simulation which predicts increases in humidity.