Reconstructing mean annual air temperatures during central Arabian humid periods over the past 8 million years

Archaeological studies in the Arabian Desert revealed past periods of wetter conditions that sustained palaeolithic human populations. Speleothem-based paleoclimate reconstructions of the Arabian Peninsula confirm short-lasting humid periods during interglacial phases in the Pleistocene, with the oldest humid phases recorded extending back to the Late Miocene. However, quantifying the amount of precipitation during humid periods has remained challenging due to the absence of key climatological information. Particularly mean annual air temperature (MAAT) is a key component of potential evapotranspiration (PET) estimates and hence the overall regional water balance. In this study, we have taken an existing Late Miocene to Late Pleistocene speleothem record to which we applied multiple newly developed paleothermometers. The data indicates that in the Late Miocene and Pliocene, wet episodes in central Arabia were up to ~4 °C warmer than current MAATs. The transition from Pliocene to Late Pleistocene central Arabian humid periods is marked by a cooling trend towards modern MAATs of ~25 °C. Based on PET estimates, past rainfall must have been much higher to exceed the modern precipitation minus PET balance. Refinement of this method will permit a more quantitative estimation of minimum precipitation amounts for the humid periods in central Arabia.