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Abstract: We explore the role of continental drift on the Phanerozoic evolution of the carbon cycle and climate with the GEOCLIM numerical model. GEOCLIM couples a 3D-climate model, a global dynamic vegetation model and a mathematical description of the chemical weathering of the continental surfaces. Twenty-one timeslices covering the whole Phanerozoic are simulated, allowing the calculation of the climate and steady-state atmospheric CO2 for each of these timeslices. We show that continental drift is a first order control parameter of the geological carbon cycle and climate. The salient features are the following: (1) the Paleozoic environment is characterized by a long term CO2 decrease; (2) the Late Permian-Late Triassic period displays very high CO2 levels; (3) atmospheric CO2 is decreasing since the Middle Cretaceous. All these features are driven by the drift of the continents and the subsequent modulation of the water cycle and weathering rates. Furthermore, continental drift imprints the long term evolution of the tropical seawater surface temperatures with periodical oscillations characterized by a frequency of about 120 Myr, in agreement with available data. Finally, we emphasize a discrepancy existing between the climate reconstructions from the most recent apatite δ18O data and the CO2 inferred from proxies. Reconstructed CO2 levels from proxies are often unrealistically low for the distant geological past. [Copyright &y& Elsevier]

Abstract: The Çal Basin formed in the late Miocene as an orogen-top rift hosting terrestrial sedimentation. The initial array of alluvial fans in a half-graben basin was replaced by an axial meandering-river system during the late Tortonian. Palaeomammal taxa indicate a mid-Turolian age of the deposits and a grass-dominated steppe ecosystem. Isotopic data from pedogenic carbonates indicate a warm, semiarid to arid climate. Subhumid to humid climatic conditions prevailed in the Pliocene, with a palustrine environment and savannah-type open ecosystem, recording a regional response to the marine flooding that terminated the Messinian ‘salinity crisis’ in the Mediterranean. Pleistocene saw re-establishment of a fluvial system in the basin with the development of an open steppe ecosystem in warm, semiarid to arid climatic conditions. The sedimentary facies analysis of the basin-fill succession, combined with biostratigraphic data, render the basin a regional reference and help to refine the Neogene tectono-climatic history of SW Anatolia. [Copyright &y& Elsevier]

Abstract: Pollen studies from core SO90-56KA recovered from the Arabian Sea off the Makran Coast (24° 509N, 65° 559E; 695 m depth) show that the end of the Holocene Humid Period, linked to the weakening of Indian monsoon fluxes, took place between 4700 and 4200 BP. Two periods of strong summer monsoon activity are identified between 5400–4200 BP and 2000–1000 BP during which the montane pollen taxa coming from the Himalayas reached the Makran coast due to increased fluvial activity of the Indus River. A contrasting period, dominated by the winter monsoon between 4200 and 2000 BP, is identified based on the presence of pollen taxa from the Baluchistan plateaus. The regional vegetation of the low- and midaltitudes, arid and semiarid, are remarkably stable from 4500 BP to the present. [Copyright &y& Elsevier]

Abstract: Using an Atmospheric Global Circulation Model, we assess the relevance of selected atmospheric mechanisms for climate evolution of Saharan and sub-Saharan regions since the Miocene. First, we test the influence of the East-African Rift System uplift on atmospheric dynamics. Although the uplift played an important role in triggering East-African rainfall, no significant impact over central and western Africa has been detected. We also analyse the feedbacks of a giant lake on the climate of Chad basin. First results infer a negative feedback of the giant lake on the water balance, as convection is weakened by the cold water surface and as water evaporated from the lake does not feed the basin hydrological cycle. Lastly, we suggest that colder than present sea surface temperatures over the Gulf of Guinea reinforce the West-African monsoon, by enhancing the moisture advection engine via stronger thermal contrast between the ocean and the continent. [Copyright &y& Elsevier]

Abstract: During the last million years, interglacial periods were characterized by sea level, Antarctic air temperature and atmospheric CO2 concentrations different from those of today. The relationship between CO2 and climate remained rather constant over these intervals, which confirms that CO2 acts as a positive feedback to insolation forcing. The thermohaline circulation and the Atlantic meridional overturning are sources of another strong positive feedback mechanism. They have been responsible for the partial melting of the West Antarctic Ice Sheet during the last interglaciation and for the amplification of the insolation forcing to trigger the last glacial inception. [Copyright &y& Elsevier]

Abstract: In order to reconstruct the past variations of the Southeast Asian monsoon intensity and estimate the sedimentary system reactivity to climatic changes in Southeast Asia over the last 450kyr, mineralogical and sedimentological analyses have been performed on the terrigenous fraction of the South China Sea sediment. End-member modelling coupled with grain size data discriminates three end-members that determine the nature and intensity of the main sediment transport vectors. Low sea-level stands are characterized by sediment reworking that allows transportation of a coarse end-member (20–40μm) to the deep-basin. By contrast, the other end-members (4–6μm; 9–13μm) are controlled by the shoreline position (sea level) and/or by changes of the rivers capacity transport (monsoon). Finally, aeolian input to the northern margin of the South China Sea can be considered negligible compared to the massive fluvial input and the reworking of the sediments. [Copyright &y& Elsevier]

Abstract: At the end of the Neoproterozoic, the Earth may have experienced important environmental changes, with a transition between two supercontinents (from Rodinia to Gondwana), extensive glaciations with ice caps reaching the Equator and the beginning of metazoan diversification. In such a context, the palaeomagnetic record can be used to constrain both the palaeogeography and the palaeoclimate (palaeolatitudinal distribution of glacial deposits). Here we present an up-to-date geochronological and palaeomagnetic database for the Neoproterozoic glacial deposits, including poles recently obtained on ‘cap carbonates’ from China, Oman, and Amazonia. The database comprises ten poles (from eight different cratons), obtained directly on the glacial deposits or on the overlying ‘cap carbonate’, and two other palaeolatitudes derived from reference poles coeval to well-dated glacial units in the same craton. The occurrence of glacial deposition at low latitudes (<30°) is attested by some good-quality poles, two of them well dated at ∼740 and ∼635Ma. Based on these poles and on reference poles obtained on igneous rocks, tentative palaeogeographic reconstructions for ∼750, ∼620, and ∼580Ma (ages for which the database has limited but still sufficient entries) were performed in order to investigate the tectonic context within which the glacial events were produced. [Copyright &y& Elsevier]

Abstract: This study concerns a core collected in Brejo do Espinho''s lagoon from Cabo Frio littoral (Brazil) submitted to dry influence of local upwelling controlled by north-east trade winds from the South Atlantic and particularly strengthened during El Niño events. Diatoms study supported by sedimentological and isotopic analyses shows dry phases infrequent before 4000 yr, a highly variable climatic phase between 3600 and 2900 yr and from 2400 yr onward a dryness enhancement. To cite this article: B. Laslandes et al., C. R. Geoscience 338 (2006). [Copyright &y& Elsevier]

Abstract: During the last glacial, characterized by a rapid climatic variability, the Greenland ice isotope–temperature relationship is biased due to changes in the hydrological cycle. An alternative palaeothermometry method, based on air isotopes, N and Ar, provides quantitative estimates of rapid temperature increases and suggests a different shape of rapid events compared to water isotope profiles. The temperature over five Dansgaard–Oeschger events (DO) on the NorthGRIP ice core is reconstructed: DO 18, 19, 20, 23 and 24 associated with warming events of 11, 16, 11, 10 and 16 °C, i.e. roughly twice larger than the amplitude suggested by the water isotopes. Together with similar efforts, our measurements permit to show a large variability between the different DO. To cite this article: A. Landais et al., C. R. Geoscience 337 (2005). [Copyright &y& Elsevier]

Abstract: On the 102- to 103-year timescale, internal reorganizations of the climate system result in abrupt climatic changes of great magnitude. Although a large body of data has been obtained, the physical mechanisms responsible for these changes are still poorly understood. Instrumental data are too short to fully record the variability of the climate system. Palaeoclimatic records provide estimates of the past atmospheric composition, temperature, precipitation, vegetation, extension of glaciers, and past ocean circulation. On the 104- to 106-year timescale, the astronomical theory of palaeoclimates accounts for most of the reconstructed variations. To cite this article: J.-C. Duplessy et al., C. R. Geoscience 337 (2005). [Copyright &y& Elsevier]

Abstract: Typical rapid climate events punctuating the last glacial period in Greenland, Europe and Antarctica are compared to two rapid events occurring under warmer conditions: (i) Dansgaard–Oeschger event 25, the first abrupt warming occurring during last glacial inception; (ii) 8.2 ka BP event, the only rapid cooling recorded during the Holocene in Greenland ice cores and in Ammersee, Germany. The rate of warming during previous warmer interglacial periods is estimated from polar ice cores to 1.5 °C per millennium, without abrupt changes. Climate change expected for the 21st century should however be at least 10 times faster. To cite this article: V. Masson-Delmotte et al., C. R. Geoscience 337 (2005). [Copyright &y& Elsevier]

Abstract: Holocene millennial climate variability is smaller than that of the last glaciation, due to the disappearance of large unstable ice sheets. Marine records show that the sea-surface temperature (SST) exhibited small variations, mainly in the high and low latitudes. They may be interpreted as a linear response to the mean annual insolation. Major changes in the hydrological cycle have been evidenced in the Asian and African monsoon area, resulting in enhanced precipitation and large river outflow in the Bay of Bengal and the Gulf of Niger. Enhanced rainfall over the Mediterranean Basin resulted in a weak circulation and sapropel formation below 800-m water depth in the eastern Mediterranean Sea. Finally small changes in the thermohaline circulation and the warm North Atlantic Drift have been detected in the Nordic Seas. The Holocene climatic variability is therefore similar to that of the Quaternary, but with small amplitude, while continents experienced large rainfall variations. To cite this article: J.-C. Duplessy et al., C. R. Geoscience 337 (2005). [Copyright &y& Elsevier]

Isotopic measurements in polar ice core have shown a succession of rapid warming periods during the last glacial period over Greenland. However, this method underestimates the surface temperature variations. A new method based on gas thermal diffusion in the firn manages to quantify surface temperature variations through associated isotopic fractionations. We developed a method to extract air from the ice and to perform isotopic measurements to reduce analytical uncertainties to 0.006 and 0.020‰ for δ15N and δ40Ar. It led to a 16±1.5 °C surface temperature variation during a rapid warming (-70 000 yr). To cite this article: A. Landais et al., C. R. Geoscience 336 (2004). [Copyright &y& Elsevier]

The astronomical theory of palaeoclimates aims to explain the recurrence of the glacial–interglacial cycles that characterizes the Quaternary climate. It is based upon the latitudinal and seasonal distributions of the energy that the Earth receives from the Sun. Their variations in time depend upon three astronomical parameters: the eccentricity of the Earth''s orbit, the inclination of its axis of rotation and the climatic precession. These astronomical variations are in turn amplified by feedback mechanisms in the climate system such as those related to the albedo, the water vapor and other greenhouse gases (CO2 and CH4), the ice sheets and the lithosphere below them. Climate models of different complexity have shown that the long-term variations of the astronomical parameters are the pacemaker of the climatic variations during the Quaternary (and other geological times) at the time scales of tens to hundreds of thousands of years. To cite this article: A. Berger, M.F. Loutre, C. R. Geoscience 336 (2004). [Copyright &y& Elsevier]

We summarize (1) knowledge about the global pre-industrial cycle of CO2 and CH4, and (2) recent reconstructions of the concentration of CO2 and CH4 in the atmosphere (CO2atm and CH4atm) based on ice cores drilled in Antarctica and Greenland. We discuss critically some difficulties in the interpretation of these reconstructions and suggest studies that should permit to better understand the factors controlling CO2atm and CH4atm variations. To cite this article: O. Marchal, J. Chappellaz, C. R. Geoscience 336 (2004). [Copyright &y& Elsevier]

Quantitative reconstruction of past sea water temperature, salinity and ventilation from marine sediment has provided an original approach to reconstruct the global ocean circulation and its past variations. These reconstructions may be compared to simulations performed either by forcing a 2-D or 3-C Ocean Circulation Model by sea surface temperature, salinity and wind stress or by forcing a fully coupled climate model (atmosphere-ocean-sea ice) by past boundary conditions such as those of the last glacial maximum (insolation, ice sheets, continental albedo and vegetation). This paper describes the main results that have been obtained over the last twenty years and discusses remaining uncertainties. Palaeoceanogaphic reconstructions have shown that the global ocean circulation was deeply different from that of today during the last glaciation and that major changes may develop in less than a few centuries. Comparable changes may occur in response to the human induced climate change of the next centuries. To cite this article: J.-C. Duplessy, C. R. Geoscience 336 (2004). [Copyright &y& Elsevier]

A large travertine outcrop south of Errachidia, southern Morocco, was studied and U/Th dated. The carbonate fraction was provided by groundwaters then, as now, from the eastern High Atlas percolating through the regional Infra-Cenomanian aquifer. There were two main periods of accumulation at ca 262 kyr BP and 20–11.5 kyr BP separated by a long discontinuity with some limited weathering and erosion and correlated in part with a period of erosion at 30–20 kyr BP further to the west. The two travertine-deposition periods suggest increased rainfall and/or cooler thermal conditions in the eastern High Atlas source regions. Massive travertine accumulation ceased at the end of the Upper Pleistocene. To cite this article: L. Boudad et al., C. R. Geoscience 335 (2003). To cite this article: L. Boudad et al., C. R. Geoscience 335 (2003). [Copyright &y& Elsevier]

The evolution of the Earth''s climate over geological time is now relatively well known. Conversely, the causes and feedback mechanisms involved in these climatic changes are still not well determined. At geological timescales, two factors play a prevailing role: plate tectonics and the chemical composition of the atmosphere. Their climatic effects will be examined using palaeoclimatic indicators as well as results of climate models. I focus primarily on the influence of continental drift on warm and cold climatic episodes. The consequences of peculiar land sea distributions (amalgamation/dispersal of continental blocks) are discussed. Plate tectonics also drive sea level changes as well as mountain uplift. Marine transgressions during the Mid-Cretaceous favoured warmth within the interiors of continents, although their effect could be very different according to the season. Mountain uplift is also an important factor, which is able to alter climate at large spatial scales. Experiments relative to climatic sensitivity to the elevation of the Appalachians during the Late Permian are discussed. To affect the whole Earth, the chemical composition of the atmosphere appears to be a more efficient forcing factor. The carbon dioxide driven by the long-term carbon cycle has influenced the global climate. Geochemical modelling simulates more or less accurately the long-term evolution of pCO2, which corresponds roughly to the icehouse/greenhouse climatic oscillations. However, the uncertainties on pCO2 are still important because different parameters involved in the long-term carbon cycle (degassing rate, chemical weathering of silicates, burial of organic matter) are not well constrained throughout the past. The chemical composition of the atmosphere is also altered by the emissions of modern volcanic eruptions leading to weak global cooling. The influence of large flood basalt provinces on climate is not yet known well enough; this volcanism may have released huge amounts of SO2 as well as CO2. At last, the chemical composition of the atmosphere may have been altered by the release of methane in response to the dissociation of gas hydrates. This scenario has been proposed to explain the abrupt warming during the Late Palaeocene. [Copyright &y& Elsevier]