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Central Asia is positioned at a crossroads linking several zones important to hominin dispersal during the Middle Pleistocene. However, the scarcity of stratified and dated archaeological material and paleoclimate records makes it difficult to understand dispersal and occupation dynamics during this time period, especially in arid zones. Here we compile and analyze paleoclimatic and archaeological data from Pleistocene Central Asia, including examination of a new layer-counted speleothem-based multiproxy record of hydrological changes in southern Uzbekistan at the end of MIS 11. Our findings indicate that Lower Palaeolithic sites in the steppe, semi-arid, and desert zones of Central Asia may have served as key areas for the dispersal of hominins into Eurasia during the Middle Pleistocene. In agreement with previous studies, we find that bifaces occur across these zones at higher latitudes and in lower altitudes relative to the other Paleolithic assemblages. We argue that arid Central Asia would have been intermittently habitable during the Middle Pleistocene when long warm interglacial phases coincided with periods when the Caspian Sea was experiencing consistently high water levels, resulting in greater moisture availability and more temperate conditions in otherwise arid regions. During periodic intervals in the Middle Pleistocene, the local environment of arid Central Asia was likely a favorable habitat for paleolithic hominins and was frequented by Lower Paleolithic toolmakers producing bifaces. Introduction Climate of arid Central Asia The timing of the earliest occupation of Central Asia Features of the lower paleolithic of Central Asia Taxonomy of early paleolithic toolmakers Materials and methods - Geographic distribution and elevation of Paleolithic assemblages - A speleothem-based proxy record of hydrological changes Results - Geographic distribution of assemblages - Speleothem age model–combining U/Th dating and layer counting - Speleothem greyscale values - Stable isotopes - Laser ablation Mg/Ca element data Discussion - Climatic factors - Hominin habitat preference - Archaeological site preservation in arid Central Asia Conclusion

Raw data and methodology

Characterising the temporal uncertainty in palaeoclimate records is crucial for analysing past climate change, for correlating climate events between records, for assessing climate periodicities, identifying potential triggers, and to evaluate climate model simulations. The first global compilation of speleothem isotope records by the SISAL (Speleothem Isotope Synthesis and Analysis) Working Group showed that age-model uncertainties are not systematically reported in the published literature and these are only available for a limited number of records (ca. 15 %, n = 107/691). To improve the usefulness of the SISAL database, we have (i) improved the database’s spatio-temporal coverage and (ii) created new chronologies using seven different approaches for age-depth modelling. We have applied these alternative chronologies to the records from the first version of the SISAL database (SISALv1) and to new records compiled since the release of SISALv1. This paper documents the necessary changes in the structure of the SISAL database to accommodate the inclusion of the new age-models and their uncertainties as well as the expansion of the database to include new records and the quality-control measures applied. This paper also documents the age-depth model approaches used to calculate the new chronologies. The updated version of the SISAL database (SISALv2) contains isotopic data from 691 speleothem records from 294 cave sites and new age-depth models, including age-depth temporal uncertainties for 512 speleothems. SISALv2 is available at https://doi.org/10.17864/1947.242 (Comas-Bru et al., 2020).

Irregularly sampled time series usually require data preprocessing before a desired time-series analysis can be applied. We propose an approach for distance measuring of pairs of data points which is directly applicable to irregularly sampled time series. In order to apply recurrence plot analysis to irregularly sampled time series, we use this approach and detect regime transitions in prototypical models and for an application from palaeoclimatatology. This approach might be useful for any method that is based on distance measuring, e.g., correlation sum or Lyapunov exponent estimation.

© 2015 Elsevier B.V. Detailed monitoring of subterranean microclimatic and hydrological conditions can delineate factors influencing speleothem based climate proxy data and helps in their interpretation. Multi annual monitoring of water stable isotopes air temperature relative humidity drip rates and PCO2 in surface soil and cave air gives detailed insight into dripwater isotopes temperature and ventilation dynamics in Mawmluh Cave NE India. Water isotopes vary seasonally in response to monsoonal rainfall. Most negative values are observed during late Indian Summer Monsoon (ISM) with a less than one month lag between ISM rainfall and drip response. Two dry season and two less well distinguishable wet season dynamic ventilation regimes are identified in Mawmluh Cave. Cave air temperatures higher than surface air result in chimney ventilation during dry season nights. Dry season days show reduced ventilation due to cool cave air relative to surface air and cold air lake development. Both high water flow and cooler than surface cave air temperatures result in air inflow during wet season nights. Wet season daytime ventilation is governed by river flow but is prone to stagnation and development of cold air lakes. CO2 monitoring indicates that PCO2 levels vary at diurnal to annual scale. Mawmluh Cave seems to act as CO2 sink during part of the dry season. While very likely additional data is needed to establish whether wet season cave air CO2 levels rise above atmospheric values. Drip behavior is highly nonlinear related to effective recharge dynamics and further complicated by human influence on the epikarst aquifer.

East Asian summer monsoon (EASM) rainfall impacts the world's most populous regions. Accurate EASM rainfall prediction necessitates robust paleoclimate reconstructions from proxy data and quantitative linkage to modern climatic conditions. Many precisely dated oxygen isotope records from Chinese stalagmites have been interpreted as directly reflecting past EASM rainfall amount variability, but recent research suggests that such records instead integrate multiple hydroclimatic processes. Using a Lagrangian precipitation moisture source diagnostic, we demonstrate that EASM rainfall is primarily derived from the Indian Ocean. Conversely, Pacific Ocean moisture export peaks during winter, and the moisture uptake area does not differ significantly between summer and winter and is thus a minor contributor to monsoonal precipitation. Our results are substantiated by an accurate reproduction of summer and winter spatial rainfall distributions across China. We also correlate modern EASM rainfall oxygen isotope ratios with instrumental rainfall amount and our moisture source data. This analysis reveals that the strength of the source effect is geographically variable, and differences in atmospheric moisture transport may significantly impact the isotopic signature of EASM rainfall at the Hulu, Dongge, and Wanxiang Cave sites. These results improve our ability to isolate the rainfall amount signal in paleomonsoon reconstructions and indicate that precipitation across central and eastern China will directly respond to variability in Indian Ocean moisture supply.

RATIONALE Carbonate clumped isotope thermometry is a powerful new technique increasingly used in many fields in earth science. Recently it has been shown that clumped isotope measurements can be performed with a Kiel carbonate preparation device and micro volume analyses allowing measurements of small (1.5 2 mg) carbonate samples. However common data correction schemes rely on measurements of gases prepared offline potentially leading to unrecognized biases in the results. METHODS We propose a new correction scheme for the Kiel device method including: (1) A pressure sensitive baseline correction (PBL) of the raw beam signals; (2) Transfer of data to the absolute reference frame; (3) Correction for acid fractionation; (4) Correction for average standard offsets; (5) When necessary correction for ?47 scale compression based on offsets among standards with different ordering state. The long term performance of the new scheme was tested with a large set of standard measurements (N = 432) obtained over the course of 15 months. RESULTS The PBL correction reliably removes composition dependent artifacts which are commonly corrected for with gas measurements and offsets observed in micro volume measurements when ion beams are imbalanced. We show that the shape of the PBL can vary strongly and needs to be properly characterized. Combined PBL and standard correction resulted in long term stability with standard deviations in ?47 of 0.012 0.016 ‰ for the five standards over the whole period close to the average error of 0.011 ‰ observed for individual measurements consisting of 10 replicate analyses. CONCLUSIONS Our correction scheme eliminates the need for routine gas measurements allowing for equal treatment of samples and standards with the Kiel device setup. While the PBL and standard data obtained over 15 months reveal variable mass spectrometer behavior they provide a robust means of correction yielding reproducible results from small carbonate samples in the long term. Copyright © 2014 John Wiley Sons Ltd.

Approximately half of the world's population lives in the tropics, and future changes in the hydrological cycle will impact not just the freshwater supplies but also energy production in areas dependent upon hydroelectric power. It is vital that we understand the mechanisms/processes that affect tropical precipitation and the eventual surface hydrological response to better assess projected future regional precipitation trends and variability. Paleo-climate proxies are well suited for this purpose as they provide long time series that pre-date and complement the present, often short instrumental observations. Here we present paleo-precipitation data from a speleothem located in Mesoamerica that reveal large multi-decadal declines in regional precipitation, whose onset coincides with clusters of large volcanic eruptions during the nineteenth and twentieth centuries. This reconstruction provides new independent evidence of long-lasting volcanic effects on climate and elucidates key aspects of the causal chain of physical processes determining the tropical climate response to global radiative forcing.