Toarcian Greenhouse Warming Shifted Climate Belts Poleward With Global Change Implications

Atmospheric convection is predicted to change in response to anthropogenic global warming, leading to a poleward expansion of the Hadley cells and associated arid climate belts. The magnitude of possible latitudinal change in the position of climate belts is, however, poorly understood. Here, we address this issue based on a case study of the early Toarcian (late Early Jurassic) Oceanic Anoxic Event (T-OAE, ∼183 Ma), one of the most significant global change events of the Phanerozoic, characterized by elevated humidity and major disturbances to terrestrial ecosystems on land. We present new leaf-wax n-alkanes δ¹³C data from the high-paleo-latitude Junggar Basin (northwest China) spanning the T-OAE and develop a time–space framework of plant-fractionation change, from low- to high-paleolatitudes across this time interval. We show that significant latitudinal changes in humidity occurred across the T-OAE (∼10°), likely because of a significant northward expansion of the low-latitude arid belts to mid-paleo-latitudes, and by inference a latitudinal expansion of the Hadley cells. This has important implications for the anthropogenic global warming and its effects on climate belts.