Palaeoclimatology

The origin of clothing is a topic that can arouse much argument and attract many different answers (and opinions). In anthropology, a consensus emerged in recent decades that not only do we have no answer, the question of why humans first invented clothes may not be answerable. This book shows that such pessimism is unfounded.

The book comprises two parts; the first part explores the origins of clothing. Evidence from ethnography, thermal physiology and climatology is covered, beginning with our biological nakedness. The key proposition is that although we have no archaeological remains of clothes from the Ice Age, we do have indirect evidence in the form of technologies linked to the manufacture of garments from animal skins – stone scrapers and blades, and bone awls and needles. When all of the evidence from archaeology, climatology, biology and ethnography is taken into account, it would seem that our ancestors first invented clothes to keep warm.

The second section looks at the impact of climate change after the last Ice Age; specifically, the problems posed by warmer and more humid conditions. The Holocene epoch witnessed a revolution in clothing technology: in many parts of the world, people changed from wearing the skins of animals to making garments from woven fabrics. The reason for changing clothes was a physiological need to manage two problems with moisture: first, increased body perspiration in the warmer weather, and second, reduced evaporation of sweat due to higher humidity levels. Porous fabrics solved these moisture issues, creating a new demand for textile fibres. The book presents evidence for production of fibres (as well as food) in early farming contexts, and shows how textiles can help resolve fundamental enigmas about the origin of agriculture.

Winner, 2020 PROSE Award for Best Book, category Archeology & Ancient History

Current chemostratigraphical studies of the Jurassic System primarily involve the use of one sedimentary component (marine organic carbon), one divalent transition metal substituted in carbonate (manganese), and two isotopic tracers: strontium-isotope ratios (87Sr/86Sr) and carbon-isotope ratios (δ13Ccarb and δ13Corg) in carbonate and in organic matter. Other parameters such as Mg/Ca and Sr/Ca ratios in calcite, oxygen-isotope ratios (ä18O) in carbonate, sulphur-isotope ratios (δ34S) in carbonate-hosted sulphate, nitrogen- isotope ratios (δ15Norg) in organic matter, osmium-isotope ratios (187Os/188Os) in black shales and neodymium-isotope ratios (143Nd/144Nd) in various mineral phases are also useful but at present give poor resolution because the database is incomplete or compromised by various factors. Stratigraphical patterns in total organic carbon (TOC) can be of either local or regional significance, depending on the lateral extent of the former nutrient-rich and productive water mass. Divalent manganese follows a similar pattern, being concentrated, most probably as a very early diagenetic phase, only in oxygen-depleted waters that typically underlie zones of elevated organic productivity. Shifts in Mg/Ca and Sr/Ca ratios on the time scale of ammonite subzones seem largely to reflect temperature changes. Strontium-isotope ratios from pristine skeletal calcite provide a global signal; δ13C values from carbonates with minimal diagenetic overprint potentially do the same, although small spatial differences in palaeo-water-mass composition may have been locally significant. Oxygen-isotope determinations on carbonate rocks and fossils generally yield values that are too scattered to be stratigraphically useful, because they reflect palaeotemperature, the evaporation–precipitation balance in sea water and the impact of any diagenesis involving an aqueous phase. Nitrogen-isotope ratios in organic matter reflect the chemistry of ancient water masses as affected by nitrate utilization and denitrification, and the stratigraphical pattern of this parameter is more likely to correlate only on a regional basis. Neodymium- isotope ratios in sea water are also water mass dependent and greatly affected by regional sources and oceanic current systems. Preliminary data on sulphur-isotope ratios in carbonates and osmium-isotope ratios in organic-rich shales, both potentially offering global correlation, indicate that these tracers may be valuable, although the records at present are not sufficiently well established to allow high-resolution regional correlation. In all cases, biostratigraphically well-dated reference sections, against which the relevant geochemical data have been calibrated, are required in the first instance. To date, studies on the stratigraphical distribution of organic carbon have been principally carried out in both northern (Boreal) and southern (Tethyan) Europe; carbon- isotope stratigraphy has been undertaken primarily, but not exclusively, on bulk pelagic sediments from the Alpine–Mediterranean or Tethyan domain; and strontium-isotope stratigraphy has been undertaken largely on calcitic skeletal material (belemnites and oysters) from northern and southern Europe. In many sections, including those containing ammonites, multi-parameter chemostratigraphy can give resolution that exceeds that attainable by classic biostratigraphical means. Strontium-isotope ratios in skeletal calcite are a particularly powerful tool for illustrating changes in sedimentary rate and revealing gaps in the stratigraphical record.

The atmospheric circulation patterns in the Southern Hemisphere have had a significant impact on the climate of the Antarctic and there is much evidence that these circulation patterns have changed in the recent past. This change is thought to have contributed to the warming trend observed at the Antarctic Peninsula over the last 50 years—one of the largest trends observed in this period on the planet. The trends associated with the continental Antarctic climate are less clear but are likely to be impacted less directly by atmospheric circulation changes. The circulation changes can be put into the context of longer timescales by considering atmospheric circulation reconstructions that have been performed using data from Antarctic ice cores. In this review paper we look at the main body of work examining: Antarctic climate trends; the understanding and impact of atmospheric circulation of the mid- to high-latitudes of the Southern Hemisphere; and the usefulness and reliability of atmospheric circulation reconstructions from Antarctic ice core data. Finally, beyond several of the more quantitative reconstructions, it is deemed that an assessment of their consistency is not possible due to the variety of circulation characteristics that the various reconstructions consider.

A new temperature reconstruction with decadal resolution, covering the last two millennia, is presented for the extratropical Northern Hemisphere (90–30°N), utilizing many palaeo-temperature proxy records never previously included in any large-scale temperature reconstruction. The amplitude of the reconstructed temperature variability on centennial time-scales exceeds 0.6°C. This reconstruction is the first to show a distinct Roman Warm Period c. ad 1–300, reaching up to the 1961–1990 mean temperature level, followed by the Dark Age Cold Period c. ad 300–800. The Medieval Warm Period is seen c. ad 800–1300 and the Little Ice Age is clearly visible c. ad 1300–1900, followed by a rapid temperature increase in the twentieth century. The highest average temperatures in the reconstruction are encountered in the mid to late tenth century and the lowest in the late seventeenth century. Decadal mean temperatures seem to have reached or exceeded the 1961–1990 mean temperature level during substantial parts of the Roman Warm Period and the Medieval Warm Period. The temperature of the last two decades, however, is possibly higher than during any previous time in the past two millennia, although this is only seen in the instrumental temperature data and not in the multi-proxy reconstruction itself. Our temperature reconstruction agrees well with the reconstructions by Moberg et al. (2005) and Mann et al. (2008) with regard to the amplitude of the variability as well as the timing of warm and cold periods, except for the period c. ad 300–800, despite significant differences in both data coverage and methodology.

This paper presents a thermal model for the prehistoric origins and development of clothing. A distinction is drawn between simple and complex clothing, a distinction which has implications for palaeolithic technological transitions and the emergence of modern human behavior. Physiological principles and paleoenvironmental data are harnessed to identify conditions requiring simple, loosely–draped garments and the more challenging conditions that demanded additional protection in the form of complex garment assemblages. No actual clothing survives from the Pleistocene, yet the archaeological record yields evidence for technological and other correlates of clothing―more evidence than is generally supposed. Major innovations and trends in the distributions and relative frequencies of lithic and other tool forms may reflect the changing need for portable insulation in the context of fluctuating ice age climates. Moreover, the non–thermal repercussions of complex clothing can be connected with archaeological signatures of modern human behavior, notably adornment. Alternative models are less parsimonious in accounting for the geographical and temporal variability of prominent technological and other behavioral patterns that vary in association with environmental changes.

Oceanic Anoxic Event 2 (OAE2), spanning the Cenomanian‐Turonian boundary (CTB), represents one of the largest perturbations in the global carbon cycle in the last 100 Myr. The δ13Ccarb, δ13Corg, and δ18O chemostratigraphy of a black shale–bearing CTB succession in the Vocontian Basin of France is described and correlated at high resolution to the European CTB reference section at Eastbourne, England, and to successions in Germany, the equatorial and midlatitude proto‐North Atlantic, and the U.S. Western Interior Seaway (WIS). Δ13C (offset between δ13Ccarb and δ13Corg) is shown to be a good pCO2 proxy that is consistent with pCO2 records obtained using biomarker δ13C data from Atlantic black shales and leaf stomata data from WIS sections. Boreal chalk δ18O records show sea surface temperature (SST) changes that closely follow the Δ13C pCO2 proxy and confirm TEX86 results from deep ocean sites. Rising pCO2 and SST during the Late Cenomanian is attributed to volcanic degassing; pCO2 and SST maxima occurred at the onset of black shale deposition, followed by falling pCO2 and cooling due to carbon sequestration by marine organic productivity and preservation, and increased silicate weathering. A marked pCO2 minimum (∼25% fall) occurred with a SST minimum (Plenus Cold Event) showing >4°C of cooling in ∼40 kyr. Renewed increases in pCO2, SST, and δ13C during latest Cenomanian black shale deposition suggest that a continuing volcanogenic CO2 flux overrode further drawdown effects. Maximum pCO2 and SST followed the end of OAE2, associated with a falling nutrient supply during the Early Turonian eustatic highstand.

The spatial context is critical when assessing present-day climate anomalies, attributing them to potential forcings and making statements regarding their frequency and severity in a long-term perspective. Recent international initiatives have expanded the number of high-quality proxy-records and developed new statistical reconstruction methods. These advances allow more rigorous regional past temperature reconstructions and, in turn, the possibility of evaluating climate models on policy-relevant, spatio-temporal scales. Here we provide a new proxy-based, annually-resolved, spatial reconstruction of the European summer (June–August) temperature fields back to 755 CE based on Bayesian hierarchical modelling (BHM), together with estimates of the European mean temperature variation since 138 BCE based on BHM and composite-plus-scaling (CPS). Our reconstructions compare well with independent instrumental and proxy-based temperature estimates, but suggest a larger amplitude in summer temperature variability than previously reported. Both CPS and BHM reconstructions indicate that the mean 20th century European summer temperature was not significantly different from some earlier centuries, including the 1st, 2nd, 8th and 10th centuries CE. The 1st century (in BHM also the 10th century) may even have been slightly warmer than the 20th century, but the difference is not statistically significant. Comparing each 50 yr period with the 1951–2000 period reveals a similar pattern. Recent summers, however, have been unusually warm in the context of the last two millennia and there are no 30 yr periods in either reconstruction that exceed the mean average European summer temperature of the last 3 decades (1986–2015 CE). A comparison with an ensemble of climate model simulations suggests that the reconstructed European summer temperature variability over the period 850–2000 CE reflects changes in both internal variability and external forcing on multi-decadal time-scales. For pan-European temperatures we find slightly better agreement between the reconstruction and the model simulations with high-end estimates for total solar irradiance. Temperature differences between the medieval period, the recent period and the Little Ice Age are larger in the reconstructions than the simulations. This may indicate inflated variability of the reconstructions, a lack of sensitivity and processes to changes in external forcing on the simulated European climate and/or an underestimation of internal variability on centennial and longer time scales.

This paper illustrates long-term trends in human population and climate from the Late Pleistocene to the Late Holocene (14,000e2500 cal. yr. BP) in order to assess to what degree climate change impacted human societies in the Near East. It draws on a large corpus of archaeo-demographic data, including anthropogenic radiocarbon dates (n ¼ 10,653) and archaeological site survey (n ¼ 22,533), and 16 hydro-climatic records from cave speleothems and lake sediments. Where possible, inferred population dynamics and climatic trends have been made spatially congruent, and their relationships have been statistically tested. Demographic proxies and palaeoclimatic records have been compared for the greater Near East as a whole and for seven major geo-cultural regions (Anatolia, Arabia, Cyprus, Iran, Levant, Mesopotamia, and South Caucasus). This approach allows us to identify regionalised patterns in population and climate trends. The results suggest a clear relationship between population and climate in the Late Pleistocene and Early Holocene (14,000e8326 cal. yr. BP) with population increasing in concomi-tance with wetter climatic conditions. During the Middle Holocene (8326-4200 cal. yr. BP) there is an increased regionalisation of demographic patterns, followed by marked interregional contrasts in the Late Holocene (4200-2500 cal. yr. BP). We identify a decoupling of demographic and climatic trends from the Middle Holocene onwards, and relate this to the existence of more complex societies. These were less vulnerable to gradual climatic shifts due to their logistical infrastructure, social organisation and technological capacity. We also assess the impact of five Rapid Climate Changes (RCC) which occurred during the study period on population levels. Although all five RCC (the so-called 10.2 k, 9.2 k, 8.2 k, 4.2 k, and 3.2 k cal. yr. BP events) are visible to some degree in our palaeoclimatic and demographic proxies, there are marked regional variations in magnitude and duration.

This paper presents an updated, extensive review of glacier fluctuations during the past 1000 years in the extratropical Andes of South America between ca. 17° and 55°S. Given the variety of environmental conditions and evidence available for glacier fluctuations across this wide latitudinal range, regional accounts are given for the Desert Andes (∼ 17°–31°S), the Andes of central Chile and Argentina (31°–36°S), and the North (36°–45°S) and South (45°–55°S) Patagonian Andes. The techniques, dating limitations, and interpretations of the glacier records along this transect are also discussed. Information on glacier fluctuations in the Desert Andes is limited to the 20th century. Documentation on past glacier variations is more abundant in the Central Chilean-Argentinean Andes, but the number of chronologies dealing with glacier fluctuations prior to the 1900s is also limited. Most records indicate that glaciers were generally more extensive prior to the 20th century, with dates of maximum expansion ranging from the 16th to the 19th centuries. The number and extent of glaciers increase significantly in the Patagonian region, where the evidence available for dating glacier variations during the past centuries is more abundant and the dating control for glacier events is generally better than in the northern parts of the study area. For some Patagonian glaciers, maximum Little Ice Age (LIA) or post-LIA advances have been precisely dated by dendro-geomorphological determinations or in situ measurements. However, for most sites, the evidence available is still preliminary and there is considerable variability in the extent and timing of events related to the maximum LIA expansion identified in most areas between the 16th and 19th centuries. Evidence is starting to appear at a growing number of sites for glacier advances during the first half of the past millennium. These events were generally less extensive than the LIA maximum pulses. Despite the occurrence of several post-LIA readvances over the past 100–110 years, most areas in the Andes of extratropical South America have experienced a general pattern of glacier recession and significant ice mass losses. The differences in the glacier histories observed at local and regional scales probably reflect the inherent limitations associated with the glacier records and/or the dating techniques used in each case together with the varying dominance of precipitation, temperature and other climatic and non-climatic factors on glacier mass balance and glacier dynamics. These differences indicate that the late Holocene glacier history of southern South America is more complex than commonly assumed. The evidence discussed in this study highlights not only the immense potential for glaciological studies of this region but also a significant need for an increased number of detailed, well-dated records of glacier fluctuations.

Understanding the ecohydrological responses of peatlands to climate change is particularly challenging over the late Holocene owing to the confounding influence of anthropogenic activity. To address this, a core spanning the last ∼2400 years from a raised bog in northern England was analysed using a comprehensive suite of proxy methods in an attempt to elucidate the drivers of change. A testate amoebae-based transfer function was used to quantitatively reconstruct changes in water table depth, supported by humification analysis and a plant macrofossil-derived hydroclimatic index. Pollen and plant macrofossil data were used to examine regional and local vegetation change, and human impacts were inferred from charcoal and geochemistry. Chronological control was achieved through a Bayesian age-depth model based on AMS radiocarbon dates and spheroidal carbonaceous particles, from which peat and carbon accumulation rates were calculated. Phases of both increased and decreased bog surface wetness (inferred effective precipitation) are present, with dry phases at c. AD 320–830, AD 920–1190 and AD 1850–present, and a marked period of increased effective precipitation at c. AD 1460–1850. Coherence with other records from across Northern Europe suggests that these episodes are primarily driven by allogenic climatic change. Periods of high bog surface wetness correspond to the Wolf, Spörer and Maunder sunspot activity minima, suggesting solar forcing was a significant driver of climate change over the last ∼1000 years. Following the intensification of agriculture and industry over the last two centuries, the combined climatic and anthropogenic forcing effects become increasingly difficult to separate due to increases in atmospheric deposition of anthropogenically derived pollutants, fertilising compounds, and additions of wind-blown soil dust. We illustrate the need for multiproxy approaches based on high-resolution palaeoecology and geochemistry to examine the recent trajectories of peatlands.

This paper provides a brief overview of the most common dating techniques applied in palaeoclimate and palaeoenvironmental studies including four radiometric and isotopic dating methods (radiocarbon, 230Th disequilibrium, luminescence, cosmogenic nuclides) and two incremental methods based on layer counting (ice layer, varves). For each method, concise background information about the fundamental principles and methodological approaches is provided. We concentrate on the time interval of focus for the INTIMATE (Integrating Ice core, MArine and TErrestrial records) community (60e8 ka). This dating guide addresses palaeoclimatologists who aim at interpretation of their often regional and local proxy time series in a wider spatial context and, therefore, have to rely on correlation with proxy records
obtained from different archives from various regions. For this reason, we especially emphasise scientific approaches for harmonising chronologies for sophisticated and robust proxy data integration. In this respect, up-to-date age modelling techniques are presented as well as tools for linking records by age equivalence including tephrochronology, cosmogenic 10Be and palaeomagnetic variations. Finally, to avoid inadequate documentation of chronologies and assure reliable correlation of proxy time series, this paper provides recommendations for minimum standards of uncertainty and age datum reporting.

ABSTRACT:
This study is the first systematic comparison of the effect of acid treatment methods on the reliability of organic carbon [C] and nitrogen [N], and carbon isotope (δ13C) values on a range of terrestrial and aquatic, modern and geological environmental materials. We investigated the 3 most common methods; (i) acidification followed by sequential deionised water rinses (“rinse method”); (ii) acidification in silver capsules (“capsule method”); and (iii) acidification by exposure to an acid vapour (“fumigation method”). We also investigated the effect of sample size and capsule type (silver and tin) on C/N ratio and δ13C values. We find (i) %C, %N, C/N and δ13C showed significant within and between method variability; (ii) disproportionate and non-linear offsets of %C, %N and C/N values after acidification within and between methods and within and between sample materials; (iii) that alterations in %C did not necessarily manifest themselves in shifts in δ13C, and vice-versa; (iv) small (~ 90 μg C) sample sizes showed consistent overestimations and inaccuracies after acidification; (v) The effect of capsule type was not significant on most samples, but did show a notable effect on our aquatic materials, generally increasing %C and %N, and producing depleted δ13C values. These findings raise cause for concern on the interpretative nature of C/N ratios and their support for carbon isotope values. The comparability between laboratories (different preparation methods) and environmental settings (amount, type and nature of OM) are also likely to be problematic. We conclude that the response of C and N concentrations in organic matter to acid treatment in environmental materials is neither negligible nor systematic.

Keywords: δ13C; C/N ratio; Method comparison; Rinse method; Capsule method; Fumigation method; environmental reconstruction

Oxygen isotopes of biogenic apatite have been widely used to reassess anomalous temperatures inferred
from oxygen isotope ratios of ancient biogenic calcite, more prone to diagenetic alteration. However, recent
studies have highlighted that oxygen isotope ratios of biogenic apatite differ dependent on used analytical
techniques. This questions the applicability of the phosphate–water fractionation equations established over
25 years ago using earlier analytical techniques to more recently acquired data. In this work we present a
new phosphate–water oxygen isotope fractionation equation based on oxygen isotopes determined on fish
raised in aquariums at controlled temperature and with monitored water oxygen isotope composition. The
new equation reveals a similar slope, but an offset of about +2‰ to the earlier published equations. This
work has major implications for paleoclimatic reconstructions using oxygen isotopes of biogenic apatite
since calculated temperatures have been underestimated by about 4 to 8 °C depending on applied techniques
and standardization of the analyses.

The magnitude and timing of a major rapid negative carbon-isotope excursion recorded in marine and terrestrial matter through the Early Toarcian (Early Jurassic) and Early Aptian (Early Cretaceous) oceanic anoxic events (OAEs) have been proposed to be the result of large methane gas-hydrate dissociation events. Here, we develop and evaluate a global carbon-isotope mass-balance approach for determining the responses of each component of the exogenic carbon cycle (terrestrial biosphere, atmosphere and ocean). The approach includes a dynamic response of the terrestrial carbon cycle to methane-related CO2 increases and climatic warming. Our analyses support the idea that both the Early Toarcian and Early Aptian isotopic curves were indicative of large episodic methane releases (~5000 and ~3000 Gt respectively) promoting warm ‘greenhouse’ conditions in the Mesozoic. These events are calculated to have increased the atmospheric CO2 concentration by ~900 and ~600 ppmv respectively and land surface temperatures by 2.5° to 3.0°C. However, we show that much of the methane released from oceanic sediments is rapidly sequestered by terrestrial and marine components in the global carbon cycle, and this effect strongly attenuated the potential for ancient methane gas-hydrate dissociation events to act as major amplifiers in global warming. An increase in oceanic carbon sequestration is consistent with the deposition of globally distributed black shales during these OAEs. Our analyses point to the urgent need for high-resolution marine and terrestrial carbon-isotope records to better characterize the nature of the Toarcian and Aptian events and improve our interpretation of their consequences for the global carbon cycle.

Highlights

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New model of ostracod distribution patterns in lacustrine turbidite layers

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Micropalaeontological tool for identifying turbidite layers in large lakes

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Documentation of event layers in cores from a remote region on the Tibetan Plateau

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Ostracod data from a large brackish high altitude lake

Here we present a multiproxy record (δ 13 C, δ 18 O, major and minor element composition, mineralogy, and low-resolution biogenic silica content) from a lacustrine succession in the Sulmona Basin, central Italy. Based on previous tephrochronological constraints and a new 40 Ar/ 39 Ar dating of a tephra matching the widespread X-6 teph-ra, the record spans the ca. 129–92 ka period and documents at sub-orbital scale the climatic and environmental changes over the Last Interglacial and its transition to the Last Glacial period. The δ 18 O composition is interpreted as a proxy for the amount and seasonality of local precipitation, whereas variations in elemental and mineralog-ical composition are inferred to reflect climatic-driven changes in clastic sediment input. The observed variations are consistent among the different proxies, and indicate that periods of reduced precipitation were marked by enhanced catchment erosion, probably due to a reduction in vegetation cover. The first part of the Last Intergla-cial shows the most negative δ 18 O values. Comparison with pollen records from the Mediterranean suggests a greater seasonality of the precipitation at this time. At millennial-to-centennial time scales, comparison of the Sulmona record with speleothem δ 18 O records from central Italy highlights a highly coherent pattern of hydrological evolution, with enhanced variability and similar events of reduced precipitation consistently recorded by each isotope record. The observed intra-interglacial variability can potentially be linked, within the uncertainties associated with each age model, to similar variations observed in sea-surface temperature records from the Mediterranean and the North Atlantic, suggesting a link between Mediterranean hydrology and North Atlantic temperature and circulation patterns that persists during periods of low ice volume.

Cyanobacteria are among the most ancient of evolutionary lineages, oxygenic photosynthesizers that may have originated before 3.0 Ga, as evidenced by free oxygen levels. Throughout the Precambrian, cyanobacteria were one of the most important drivers of biological innovations, strongly impacting early Earth's environments. At the end of the Archean Eon, they were responsible for the rapid oxygenation of Earth's atmosphere during an episode referred to as the Great Oxidation Event (GOE). However, little is known about the origin and diversity of early cyanobacterial taxa, due to: (1) the scarceness of Precambrian fossil deposits; (2) limited characteristics for the identification of taxa; and (3) the poor preservation of ancient microfossils. Previous studies based on 16S rRNA have suggested that the origin of multicellularity within cyanobacteria might have been associated with the GOE. However, single-gene analyses have limitations, particularly for deep branches. We reconstructed the evolutionary history of cyanobacteria using genome scale data and re-evaluated the Precambrian fossil record to get more precise calibrations for a relaxed clock analysis. For the phylogenomic reconstructions, we identified 756 conserved gene sequences in 65 cyanobacterial taxa, of which eight genomes have been sequenced in this study. Character state reconstructions based on maximum likelihood and Bayesian phylogenetic inference confirm previous findings, of an ancient multicellular cyanobacterial lineage ancestral to the majority of modern cyanobacteria. Relaxed clock analyses provide firm support for an origin of cyanobacteria in the Archean and a transition to multicellularity before the GOE. It is likely that multicellularity had a greater impact on cyanobacterial fitness and thus abundance, than previously assumed. Multicellularity, as a major evolutionary innovation, forming a novel unit for selection to act upon, may have served to overcome evolutionary constraints and enabled diversification of the variety of morphotypes seen in cyanobacteria today.