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The National Center for Atmospheric Research-Community Climate System Model (NCARCCSM) is used in a coupled atmosphere-ocean-sea-ice simulation of the Last Glacial Maximum (LGM, around 21,000 years ago) climate. In the tropics, the simulation shows a moderate cooling of 3 °C over land and 2 °C in the ocean in zonal average. This cooling is about 1 °C cooler than the CLIMAP sea surface temperatures (SSTs) but consistent with recent estimates of both land and sea surface temperature changes. Subtropical waters are cooled by 2–2.5 °C, also in agreement with recent estimates. The simulated oceanic thermohaline circulation at the LGM is not only shallower but also weaker than the modern with a migration of deep-water formation site in the North Atlantic as suggested by the paleoceanographic evidences. The simulated northward flow of Antarctic Bottom Water (AABW) is enhanced. These deep circulation changes are attributable to the increased surface density flux in the Southern Ocean caused by sea-ice expansion at the LGM. Both the Gulf Stream and the Kuroshio are intensified due to the overall increase of wind stress over the subtropical oceans. The intensified zonal wind stress and southward shift of its maximum in the Southern Ocean effectively enhances the transport of the Antarctic Circumpolar Current (ACC) by more than 50%. Simulated SSTs are lowered by up to 8 °C in the midlatitudes. Simulated conditions in the North Atlantic are warmer and with less sea-ice than indicated by CLIMAP again, in agreement with more recent estimates. The increased meridional SST gradient at the LGM results in an enhanced Hadley Circulation and increased midlatitude storm track precipitation. The increased baroclinic storm activity also intensifies the meridional atmospheric heat transport. A sensitivity experiment shows that about half of the simulated tropical cooling at the LGM originates from reduced atmospheric concentrations of greenhouse gases. [ABSTRACT FROM AUTHOR]

A modelling experiment with changes in vegetation types at the Last Glacial Maximum (21 ka BP) is performed by using an AGCM coupled with a simplified simple biosphere model (AGCM+SSiB). The results show that the decrease in temperature is large in Tibet and Eastern Asia at 21 ka. The amplitudes of the decrease vary with seasons and locations. Annual mean temperature decreases between 13 °C and 2 °C. Summer and annual precipitation in eastern China at 21 ka is only about 50% of that at present; while little more or unchanged precipitation appears in northwest, west and southwest of China. The effective precipitation (P–E) shows much drier conditions in eastern and southeastern China than today. A comparison with geological evidences of lake-status and pollen-based vegetation shows that this simulation is in broad scale agreement with the geological records. The changes by using palaeo-vegetation data to prescribe land surface show improved signals in the 21 ka climate simulations in East Asia. This result encourages us to study the potential causes, feedbacks and mechanisms of palaeoclimate changes using the AGCM+SSiB modelling approach continuously. [ABSTRACT FROM AUTHOR]

A coupled atmosphere–ocean–sea ice–land surface climate system model developed at the Canadian Centre for Climate Modelling and Analysis (CCCma) is used to investigate the response to glacial ice-sheet topography and decreased CO2 representative of the last glacial maximum (LGM, roughly 21,000 years before present). Imposing these glacial boundary conditions leads to a strong and rapid climate adjustment, first in the atmosphere, and then in the ocean. We describe the model and boundary conditions and analyze the initial transient response. In a subsequent paper we analyze the near-equilibrium response. During the transient phase, surface air temperature rapidly decreases with time. The rapid cooling over the Laurentide and Fennoscandian ice sheets introduces a strong inter-hemispheric asymmetry. Sea surface temperature also decreases and after 80 years of integration, ocean surface temperature has decreased by 3 °C and global surface air temperature by 5 °C. The expected overall cooling is contrasted by marked regions of unexpected localized ocean surface warming and the retreat of sea ice in the northern North Atlantic and in the high latitude Southern Ocean. This strong transient behavior, associated with more vigorous oceanic convection at these high latitudes, represents the localization of the initial response in areas remote from the direct forcing change. The strength of the North Atlantic (Southern Ocean) overturning stream function, associated with the formation of North Atlantic Deep Water (Antarctic Bottom Water), increases from 12 to 36 Sv (2 to 26 Sv). There is a marked increase in the Antarctic Circumpolar Current transport as well (from 80 to 140 Sv), even though the wind stress decreases over the Southern Ocean, presumably as a consequence of the enhanced bottom pressure torque due to an increase in the density and the formation of Antarctic Bottom Water. Both precipitation and evaporation decrease on average with time and the change in the hydrological cycle modifies sea surface salinity (SSS). SSS increases in the Arctic Ocean due to a decrease in river runoff while it decreases in the North Atlantic due to an increase in river runoff and an increase in precipitation minus evaporation. The initial (and near equilibrium) climate response to LGM forcing in the fully coupled atmosphere–ocean climate model is quite different from that in the associated atmosphere-mixed layer ocean model due to very strong oceanic feedbacks. This is especially evident where oceanic convection is active. The anomalously warm surface temperature, especially in the Southern Ocean, and the marked increase in the overturning circulation are transient features of the response to imposed LGM boundary conditions which moderate or reverse as the system approaches equilibrium (as described in the companion paper). Other differences with the mixed layer simulation include a considerably colder tropical Pacific and the development of a La Niña-like response both of which are absent in the mixed layer simulations. [ABSTRACT FROM AUTHOR]

Investigates the glacial-interglacial stability of ocean hydrogen-ion concentration (pH). Inference of the stability from foraminifer dissolution rates; Role of ocean in the global carbon cycle; Absence of changes in the whole ocean pH.

Investigates the reduced nitrogen fixation in the glacial ocean. Explanation of the lower atmospheric carbon dioxide concentrations during the glacial periods; Stimulation of the productivity of marine phytoplankton; Influence of iron on the increase in the rate of marine nitrogen fixation.

To explore processes involved in glacial inception at 116 kaBP, the response of an atmospheric general circulation model (AGCM) to changes in lower boundary conditions is investigated. Two 116 kaBP experiments are conducted to examine the importance of sea surface conditions (sea surface temperature and sea ice distribution): one with the present-day sea surface conditions, and the other with 116 kaBP sea surface conditions. These two different sea surface conditions are obtained from simulations using an earth system climate model of intermediate complexity. Perennial snow cover occurred over the Canadian Archipelago under 116 kaBP orbital and CO2 forcing with present-day "warm" sea surface conditions, and further expanded over northeastern Canada when 116 kaBP "cool" sea surface conditions were applied. The net positive accumulation in northeastern Canada, with little in Alaska, is in good agreement with geological records. Two additional 116 kaBP experiments are conducted to examine the combined importance of sea surface conditions and land surface conditions (vegetation): one with the present-day sea surface and modified land surface conditions, and the other with 116 kaBP sea surface and modified land surface conditions. Modifying vegetation, based on cooling during summer induced by 116 kaBP sea surface conditions, leads to much larger areas of perennial snow cover. Only when 116 kaBP sea surface conditions are applied, is a realistic global net snow accumulation rate obtained. Contrary to the earlier ice age hypothesis, our results suggest that the capturing of glacial inception at 116 kaBP requires the use of "cooler" sea surface conditions than those of the present climate. Also, the large impact of vegetation change on climate suggests that the inclusion of the vegetation feedback is important for model validation, at least, in this particular period of Earth history. [ABSTRACT FROM AUTHOR]

Freezing dilute aqueous solutions of certain oxidizable species such as nitrite and sulfite can promote the rate of autoxidation, instead of retarding it. Experiments show that nitrite and sulfite undergo rapid oxidation to nitrate and sulfate, respectively, in high yield (>90% under certain conditions) when their dilute (100 µM) aqueous solutions are frozen for 10.60 min. at -10 to -40°C. For example, the pseudo-second-order rate constant for nitrite autoxidation, k′, defined in d[NO3-]/dt = 2k′[HNO2]², reaches a maximum value of 117 ± 14 M-1s-1 at -15.5°C. This counterintuitive result is hypothesized to be the result of a freeze-concentration effect that occurs when reactants are concentrated into liquid micropockets ahead of the advancing ice front. Oxidation by hydrogen peroxide is also accelerated upon freezing. Since the yields and rates may be high compared to other competing pathways, this process may be significant where freeze/thaw cycles occur naturally, e.g., in glaciating clouds, snow packs, glaciers, and melt ponds on polar sea ice. [ABSTRACT FROM AUTHOR]

Presents a high-resolution multi-proxy lacustrine record of climate change during the last interglacial period, based on oxygen isotopes in diatom silica, diatom assemblages and pollen-climate transfer functions from the Ribains maar in France. Absence of a cold event interrupting the warm interglacial climate; Confirmation that the last interglacial period in southwestern Europe was a time of climatic stability.

Presents information on a study that sought evidence for intensified deep Pacific Ocean inflow and ventilation during the glacial period. Specific location and features of the Ocean Drilling Program Site 1123; Proxies used to examine the variation in the thermohaline circulation; Implication of the multitaper spectral analysis of the silt mean size record on the spectral peaks of each orbital frequency.

Examines the timing of dust fluxes to the North Atlantic Ocean in relation to the climate records from the Vostok ice core in Antartica around the time of the penultimate deglaciation. Pattern and timing of carbon dioxide variations recorded by the Vostok ice core; Measurement of the magnetic remanence acquired at high applied magnetic fields of the sediments; Methodology.

To study glacial termination and related feedback mechanisms, a continental ice dynamics model is globally and asynchronously coupled to a physical climate (atmosphere-ocean-sea ice) model. The model performs well under present-day, 11 kaBP (thousand years before present) and 21 kaBP perpetual forcing. To address the ice-sheet response under the effects of both perpetual orbital and CO2 forcing, sensitivity experiments are conducted with two different orbital configurations (11 kaBP and 21 kaBP) and two different atmospheric CO2 concentrations (200 ppmv and 280 ppmv). This study reveals that, although both orbital and CO2 forcing have an impact on ice-sheet maintenance and deglacial processes, and although neither acting alone is sufficient to lead to complete deglaciation, orbital forcing seems to be more important. The CO2 forcing has a large impact on climate, not uniformly or zonally over the globe, but concentrated over the continents adjacent to the North Atlantic. The effect of increased CO2 (from 200 ppmv to 280 ppmv) on surface air temperature has its peak there in winter associated with a reduction in sea-ice extent in the northern North Atlantic. These changes are accompanied by an enhancement in the intensity of the meridional overturning and poleward ocean heat transport in the North Atlantic. On the other hand, the effect of orbital forcing (from 21 kaBP to 11 kaBP) has its peak in summer. Since the summer temperature, rather than winter temperature, is found to be dominant for the ice-sheet mass balance, orbital forcing has a larger effect than CO2 forcing in deglaciation. Warm winter sea surface temperature arising from increased CO2 during the deglaciation contributes to ice-sheet nourishment (negative feedback for ice-sheet retreat) through slightly enhanced precipitation. However, the precipitation effect is totally overwhelmed by the temperature effect. Our results suggest that the last deglaciation was initiated through increasing summer insolation with CO2 providing a powerful feedback. [ABSTRACT FROM AUTHOR]

Presents a study to investigate the stability of glacial climate and the abrupt changes in climate known as Dansgaard-Oeschger and Heinrich events. Background; Methods; Results; Conclusion that only one mode of Atlantic Ocean circulation is stable.

Under the framework of the Palaeoclimate Modelling Intercomparison Project (PMIP), 17 climate models, 16 of which are atmospheric general circulation models, have been run to simulate the climate of the Last Glacial Maximum (21 000 years ago) using the same set of boundary conditions. Parallel to these numerical experiments, new, consistent, data bases have been developed on a continental scale. The present work compares the range of the model responses to the large perturbation corresponding to the conditions of the Last Glacial Maximum with consistently derived climate reconstructions from pollen records over Europe and western Siberia. It accounts for the differences in the model results due to the models themselves and directly compares this “error bar” due to the models to the uncertainties in the climate reconstructions from the pollen records. Overall the Last Glacial Maximum climate simulated by the models over western Europe is warmer, especially in winter, and wetter than the one depicted by the reconstructions. This is the region where the reconstructed increase in temperature, precipitation and moisture index from the Last Glacial Maximum to the present conditions is largest. The same disagreement, but of smaller amplitude, is found over Central Europe and the eastern Mediterranean Basin, while models and data are in broad agreement over western Siberia. The numerous modelling results allow a study of the link between the changes in atmospheric circulation and those in temperature, and an interpretation of the discrepancies in precipitation in terms of those in temperature. [ABSTRACT FROM AUTHOR]

Discusses physical evidence of pre-sixteenth century glacial advances in the North Atlantic region. Canada; Greenland; Iceland; Spitsbergen; Scandinavia.

The climate at the Last Interglacial Maximum (125 000 years before present) is investigated with the atmosphere-ocean general circulation model ECHAM-1/LSG and with the climate system model of intermediate complexity CLIMBER-2. Comparison of the results of the two models reveals broad agreement in most large-scale features, but also some discrepancies. The fast turnaround time of CLIMBER-2 permits one to perform a number of sensitivity experiments to (1) investigate the possible reasons for these differences, in particular the impact of different freshwater fluxes to the ocean, (2) analyze the sensitivity of the results to changes in the definition of the modern reference run concerning CO2 levels (preindustrial versus “present”), and (3) estimate the role of vegetation in the changed climate. Interactive vegetation turns out to be capable of modifying the initial climate signals significantly, leading especially to warmer winters in large parts of the Northern Hemisphere, as indicated by various paleodata. Differences due to changes in the atmospheric CO2 content and due to interactive vegetation are shown to be at least of the same order of magnitude as differences between the two completely different models, demonstrating the importance of careful experimental design. [ABSTRACT FROM AUTHOR]

Deals with a study on the two-step character of the last deglaciation recorded in tropical Maar Lake Huguangyan, China. Indications that the geographical extent and character of climactic oscillations of the last deglaciation are not well known; Materials and methods; Results and reconstruction of paleoclimate; Conclusion of the study.

Presents information on a study which used geological data from Chinese lake status database to reconstruct the Last Glacial Maximum (LGM) climate from China. Overview of the lake status data for the LGM; Methods used in the study; Lake-status based reconstruction of the LGM climate; Paleoclimate simulations on precipitation and precipitation-evaporation.

Since the 1976 publication of the CLIMAP ice age sea surface temperature (SST) reconstruction showing a 1–2 ∘C tropical cooling a substantial debate has arisen as to whether tropical SSTs may instead have been 4–5∘ colder than present. Herein I review the arguments for large SST variations and question a number of key findings, particularly the validity of ice-age coral SST estimates and “down-projecting” tropical snowline changes to the surface. GCM results indicate that an intermediate solution requiring ∼2.5 ∘C warm pool cooling is consistent with most quantitative low elevation surface land data and is small enough to allow the persistence of tropical biota in the ocean during glacial times. The proposal reduces estimated ice-age climate sensitivity (for a doubling of CO2) from a “high-end” sensitivity of about 4.5 ∘C (for a 5–6 ∘C tropical cooling) to a “mid-range” sensitivity of about 3.0 ∘C for a 2.5 ∘C warm-pool decrease. [ABSTRACT FROM AUTHOR]

Investigates the glacial-interglacial linkages between Antarctic air temperature and atmospheric carbon dioxide (CO2) variations. Factors behind low glacial CO2 levels; Association of deep-water ventilation with Antarctic sea-ice coverage and wintertime coverage; Use of ice-core measurements.

The article discusses various studies on the Kråkenes Project, a multidisciplinary investigation of late-glacial and early-Holocene ecosystem changes associated with large-scale rapid environmental changes that occurred between 12,300 and 8,800 14C yr BP in Kråkenes Lake, Norway, published within the issue.

Presents research on rapid changes in the mechanism of ocean convection during the last glacial period. Use of stable isotope and other sedimentological data to reveal specific oceanic reorganizations during these rapid climate-change events; Two mechanisms by which deep water in the Nordic Seas was generated during the latter part of the last glacial period; Implications for climatic changes.

Looks at the climatic implications of the revised sea surface temperature field for the Last Glacial Maximum using an atmospheric general circulation model. Observations of modified seasonal air temperatures by cooler equatorial oceans; Suggestion that study results may help to resolve disagreements between oceanic and continental proxy climate data; Suggestion of a wind-related mechanism for enhancing the export of water vapour from the Atlantic to the Indo-Pacific oceans.

Discusses a study which investigated the loess section of Zhaitang, Beijing, China and identified a weakly developed paleosol at the transition from the last interglacial to the last glacial which represent the warming reversal at the last interglacial-last glacial transition (LILGT). Evidence of the climatic reversal at the LILGT; Correlation of LILGT.

In terms of Earth-Sun geometry, the Milankovitch theory has succesfully explained most of the cyclic palàepclimatic variations during the history of the Earth, especially in the Quaternary. In this paper, the authors suggest that the impact of extraterrestrial bodies on the Earth may be another mechanism to cause palaeoclimatic cycles, global environmental changes and new glacial periods. Based on geological and geochemical records in the boundary layers produced by six huge Cenozoic bolide-impact events (65, 34, 15, 2.4, 1.1, 0.73 Ma B.P.), including those at 34, 15, 1.1 and 0.73 Ma B.P. which are represented by four famous tektite-strewn fields, the process and mechanics of palaeoclimatic cycles and global environmental catastrophes induced by extraterrestrial impact are discussed in detail. Impact-generated dust, soot and aerosol floating in the stratosphere could result in short-term ( < 1 year), rapid drop in temperature immediately after impact. Through self-regulation of the Earth's climate system, the temperature at the surface slowly went up within 100a and maintained stable for a long time at 250K. If there were no other factors leading to the break-down of the newly-established equilibrium, a new glacial period would be initiated. Estimating from the thickness of δ[sup 13]C and δ[sup 18]O anomalies in sediments across the impact boundary layer and deposition rate, the duration of two stages of the palaeoclimate cycle in the form of cold weather—greenhouse effect—normal weather was 10[sup 4] - 10[sup 5]a, respectively. The conclusion deduced from the above model is supported by palaeotemperature change recorded by oxygen isotope in sediments across the impact boundary layer. [ABSTRACT FROM AUTHOR]

Finds that glacial to interglacial climate changes have been related to organic carbon cycling in oceanic surface waters. Development of sedimentary tracers of past marine biological production; Organic biomarker compounds established for tracing the contributions of different planktonic groups to organic carbon in sediments; The four biomarkers, dinosterol, alkenones, brassicasterol and chlorins; Biological production of the Arabian Sea;

Presents evidence for a general relationship between low-latitude monsoonal climate variability and the rapid temperature fluctuations of high northern latitudes that are recorded in the Greenland ice records. How periods of lowered southwest monsoonal intensity are associated with intervals of high-latitude atmospheric cooling and the injection of melt water into the North Atlantic basin; Implications of the evidence.

Presents research which used a global coupled ocean-atmosphere model of intermediate complexity to simulate the equilibrium climate of today and the Last Glacial Maximum, 21,000 years ago. Prediction of atmospheric and oceanic circulations; Avoidance of flux adjustments; Changes in oceanic circulation in glacial cooling.

Uses a series of climate simulations to show that maintaining ocean heat transport at close to present-day values leads to enhanced cooling, particularly in the tropics. The suggestion that near-modern ocean heat transport may have been sustained in all ocean basins during the Last Glacial Maximum; How the climate model simulations were created. INSET: Ocean heat convergence and transport calculations..

Describes the record of ocean oxygenation and circulation from the Santa Barbara basin in the northeast Pacific Ocean which correlates well with the Greenland ice-core records. Instability of the glacial climate in the Northern Hemisphere revealed by interstadials or Daansgard-Oeschger events; Ventilation changes seen in the Gulf of California.

Suggests that the 100,000-year terrestrial glacial climate cycle might be linked to periodic changes in the accretion of cosmic dust to earth. Source and use of helium-3 in oceanic sediments; Variations in the accretion rates; Oscillating period of sediments from the Mid-Atlantic Ridge.

Focuses on climate variation over the last interglacial period recorded in the lake carbonate deposit of eastern Qinghai-Xizang Plateau, with reference to a study conducted. Methodology used to conduct the study; Results of the study.

Presents high-resolution records of foraminiferal assemblages and ice-rafted detritus from North Atlantic cores for the interval 65,000 to 135,000 years ago. Extension of surface-ocean record to Eemian period; Correlation with Greenland Ice Core Project (GRIP) ice-cores.

Changes in velocity and temperature of ice are the internal driving factors accelerating glacial regression under the condition of climatic warming. To evaluate glacial response to climate from the perspective of the internal driving forces of glaciers, we used a two-dimensional force balance and energy balance model to simulate the ice velocity and temperature of the No. 8 glacier (H8) in Tianshan Mountains, China. We analyzed the influence of dynamic characteristics caused by climatic warming on glacial changes. The simulation results of ice velocity showed: when the atmospheric temperature changed by 2 °C, the maximum velocity increased from 9 to 20 ma−1, and the total average ice velocity increased from − 9.2 to − 6.9 °C. Apparently, climatic warming could lead to an increase in ice flux. In addition, to analyze the effect of velocity increment on glacial changes, we set the difference mass balance to simulate the glacier change in the future. And the results showed that climatic warming would increase the glacial area in terminus in a short period of time and weaken the ice reserves at upstream. Under the condition of continuous climatic warming, it would accelerate the loss of glacial area and ice reserves. [ABSTRACT FROM AUTHOR]

Attempts to place Palaeolithic finds within a precise climatic framework are complicated by both uncertainty over the radiocarbon calibration beyond about 21,500 14C years bp and the absence of a master calendar chronology for climate events from reference archives such as Greenland ice cores or speleothems. Here we present an alternative approach, in which 14C dates of interest are mapped directly onto the palaeoclimate record of the Cariaco Basin by means of its 14C series, circumventing calendar age model and correlation uncertainties, and placing dated events in the millennial-scale climate context of the last glacial period. This is applied to different sets of dates from levels with Mousterian artefacts, presumably produced by late Neanderthals, from Gorham’s Cave in Gibraltar: first, generally accepted estimates of about 32,000 14C years bp for the uppermost Mousterian levels; second, a possible extended Middle Palaeolithic occupation until about 28,000 14C years bp; and third, more contentious evidence for persistence until about 24,000 14C years bp. This study shows that the three sets translate to different scenarios on the role of climate in Neanderthal extinction. The first two correspond to intervals of general climatic instability between stadials and interstadials that characterized most of the Middle Pleniglacial and are not coeval with Heinrich Events. In contrast, if accepted, the youngest date indicates that late Neanderthals may have persisted up to the onset of a major environmental shift, which included an expansion in global ice volume and an increased latitudinal temperature gradient. More generally, our radiocarbon climatostratigraphic approach can be applied to any ‘snapshot’ date from discontinuous records in a variety of deposits and can become a powerful tool in evaluating the climatic signature of critical intervals in Late Pleistocene human evolution. [ABSTRACT FROM AUTHOR]

The controls that affect the structure and timing of terminations are still poorly understood. We studied a tufa deposit from the Iberian Peninsula that covers Termination II (T-II) and whose chronology was synchronized to speleothem records. We used the same chronology to synchronize ocean sediments from the North Atlantic to correlate major climate events in a common timescale. We identify two stages within T-II. The first stage started with the increase of boreal summer integrated solar insolation, and during this stage three millennial climate oscillations were recorded. These oscillations resulted from complex ocean–atmosphere interactions in the Nordic seas, caused by the progressive decay of Northern Hemisphere ice-sheets. The second stage commenced after a glacial outburst that caused the collapse of the Thermohaline Circulation, a massive Heinrich event, and the onset of the Bipolar Seesaw Mechanism (BSM) that eventually permitted the completion of T-II. The pace of the millennial oscillations during the first stage of T-II controlled the onset of the second stage, when the termination became a non-reversible and global phenomenon that accelerated the deglaciation. During the last the two terminations, the BSM was triggered by different detailed climate interactions, which suggests the occurrence of different modes of terminations. [ABSTRACT FROM AUTHOR]

The article presents the principle of geocentric axial dipole model, and analysed the paleo-magnetization of salt bedded rocks from 2.5 billion years of the world. The data indicates that the evaporites have been deposited predominantly between latitudes 10 degrees and 35 degrees, supporting uniformitarianism. The author disagrees with the principle of working from the known to the unknown, however, considers the work is commandable and well documented.

Discusses a study by Richard Bintanja and colleagues who used a novel and elegant method to investigate further the ratio of oxygen isotopes contained in benthic foraminifera to explore past ice-volume variations. Challenge of disentangling the different contributions to the signal in benthic foraminifera, the fossilized remains of single-celled organisms that lived on or close to the ocean floor; Variation of the ratio of the oxygen isotopes [sup 18]O and [sup 18]O in the shells of benthic foraminifera with the depth of the sediments in which they are buried; Choosing the benthic isotope record that should be used to drive the model.

Presents research using oxygen-isotope compositions and species assemblages of planktonic foraminifera of a shallow-water sea-floor sediment sample to estimate the sea surface temperature (SST) in the subtropical North Pacific during the last glacial age. Contrary estimates of the CLIMAP project; Implications for the proper understanding of global climate sensitivity to SST fluctuations.

Presents a study on the role of orbitally induced changes in tundra area in the onset of glaciation. Simulation of incipient glaciation using three-dimensional general circulation models; Effects of climate feedback from high-latitude tundra expansion.

Presents models of thermohaline circulation in the abrupt warming after the deposition of ice-rafted debris called Heinrich events. Evidence of climatic oscillations during the last glacial period; Description and implications of Heinrich events; Qualitative features of climate circulations.

Mountain massif Munku-Sardyk presents the highest mountain range and adjacent Stanovoy ridge highlands of the Eastern Sayan. There is situated modern glaciation site which was the most studied in the course of last 160 years. This periglacial area experienced different periods of cooling and warming in the Holocene and retained traces of the Sartan glaciation of Subboreal (3000-5000 years ago), the Little Ice Age, the evidences of Holocene optimum and general warming last time. The authors examined the variability of activity of modern glaciation and variation of natural conditions of the periglacial zone on climate and on dendrochronological data. Results of larch and Siberian stone pine growth data were revealed at the higher border of forest communities. Analysis of the growth of the “fossil” tree in the Holocene optimum showed that the absolute magnitude of its increment was two times higher than for up-to-date long-lived trees. Identified periods of the Peretolchin glacier retreat in 1900-1965 and 1983-2000 years took place with increased growth of trees and the rate of sedimentation in proglacial lake, and vice versa glacier advance on in 1965-1980 years was accompanied by slowing of tree increments and reduction in sedimentation rate. Since 2000, there has been growth of trees instability associated with a decrease in average monthly summer temperatures. [ABSTRACT FROM AUTHOR]

The article focuses on palaeoclimatology. Topics discussed include evidence for a Neoproterozoic Snowball Earth in the sedimentary record which has been controversial; a weathered horizon preserved in sedimentary rocks from Svalbard; and how it may provide a rare signature of prolonged global glaciation.

The article reports on Antarctic ice-core data offering insights into interhemispheric climatic changes during the last glacial period in the Northern Hemisphere. The authors discuss warming trends known as Dansgaard–Oeschger (DO) events, explore the presence of hemispheric climate coupling, and examine the Atlantic meridional overturning circulation (AMOC).

The article discusses a research study by E. Bohm and colleagues on the link between ocean paleocirculation and climate change. Topics noted include the multimode modes concept of ocean circulation during the last glacial cycle, production of deep water in the North Atlantic, ratio of protactinium to thorium isotopes, and stability of oceanic heat transport.

The article presents a research that investigates the impact of the declining Atlantic circulation overturning, during the previous deglacial warming, on the Northern Hemisphere. Researchers analyzed the composition of hydrogen isotopes of the lipids of lake sediments to determine the vegetation shift in 1844, after the first decline of temperatures in the Younger Dryas. They suggested that the changes in temperature are associated to the amount and source of moisture that reached the region.

The article focuses on the use of models of emissions, climate, and vegetation to show how the increase in methane volume could have originated from natural causes. It states that from the combined use of methane-concentration and isotopic data, it indicates that the main cause of the glacial-interglacial increase is the strength of wetland methane sources. It mentions that the model experiments enable the authors to define which regions contributed to the global pattern of methane emissions.

The article focuses on a study of M. R. Kaplan and colleagues who incorporated stringent field investigations and modern geochronology to investigate the late-glacial climate change in the Southern Alps of New Zealand. It notes that during the late-glacial time, both the Northern and Southern Hemispheres went to phases of cooler climate that disrupted the normal warming of the earth. It asserts that the study is a valuable chronological test that is crucial for understanding climate variability.

The article discusses the assessment of sea level throughout the last integracial which is nearly 125,000 years ago as presented by R. E. Kopp and colleagues. It notes that the consolidation of data and modelling with the use of a probabilistic approach shows that sea level during the last interglacial was much higher than in the twenty-first century. It mentions that the increase level of global sea developed from both the increase of warming water or thermosteric change and the addition of new water from melting ice on land or eustatic change.

The article focuses on the study conducted by L. C. Sime and colleagues describing the ways on how they have used climate- model simulations to re-examine the temperature history that has been recorded by the isotopic composition of three long ice cores from Antarctica. The researchers conclude that the previous estimates of the southern-polar warmth during the Eemian and other interglacials have been underestimates. Sime along with his colleagues suggest that temperatures that have peaked at about 6 kelvin higher than at present, about double the usually accepted figure.

The article discusses two research papers concerning the generating of data to allow human knowledge of climatic conditions in past epochs to serve as a model for future sea-level rise resulting from global warming. The papers focus on the early to middle Pliocene Period to reconstruct Antarctica's glacial history. Observational evidence was obtained from a sediment core taken from beneath the Ross Ice Shelf, providing the authors with insight about cycles dictating summer sea ice and tectonic forces.