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The Kyoto Protocol’s Clean Development Mechanism (CDM) allows developed countries to meet part of their obligational emission reductions by carrying out emission reduction projects in developing countries. China imposed a price floor to the CDM carbon credits produced in China through its price review policy. Scholars have not agreed on the purpose of China’s price review policy. With a theoretical model and a coherent empirical study, the present study shows that the price floor imposed by China’s price review is more likely to protect those domestic project owners against price discrimination, rather than to distort the CDM market. Nevertheless, China’s price review has its own flaws. Although a regression study shows month of approval, types of projects and location of project can explain 55% of price floor designation, the operation of price review remains quite random and unpredictable in individual cases. This would bring extra bureaucratically uncertainty on its way to curb market uncertainty. Its function can be fulfilled by alternative policy tools with better economic efficiency and legal legitimacy, such as mandatory price disclosure and trading forum, which doesn’t have such drawback, but still be able to alleviate possible price discrimination in individual cases.
The Upper Cambrian Lower Qiulitag Group in the Tarim Basin, NW China, is overwhelmingly composed of cyclic dolomites. Based on extensive field investigations and facies analysis from four outcrop sections in the Bachu-Keping area, northwestern Tarim Basin, four main types of facies are recognized: open-marine subtidal, restricted shallow subtidal, intertidal, and supratidal facies, and these are further subdivided into ten lithofacies. In general, these facies are vertically arranged into shallowing-upward, metre-scale cycles. These cycles are commonly composed of a thin basal horizon reflecting abrupt deepening, and a thicker upper succession showing gradual shallowing upwards. Based on the vertical facies arrangements and changes across boundary surfaces, two types of cycle: peritidal and shallow subtidal cycle, are further identified. The peritidal cycles, predominating over the lower-middle Lower Qiulitag Group, commence with shallow subtidal to lower intertidal facies and are capped by inter-supratidal facies. In contrast, the shallow subtidal cycles, dominating the upper Lower Qiulitag Group, are capped by shallow-subtidal facies. Based on vertical lithofacies variations, cycle stacking patterns, and accommodation variations revealed by Fischer plots, six larger-scale third-order depositional sequences (Sq1-Sq6) are recognized. These sequences generally consist of a lower transgressive and an upper regressive systems tract. The transgressive tracts are dominated by thicker-than-average cycles, indicating an overall accommodation increase, whereas the regressive tracts are characterized by thinner-than-average peritidal cycles, indicating an overall accommodation decrease. The sequence boundaries are characterized by transitional zones of stacked thinner-than-average cycles, rather than by a single surface. These sequences can further be grouped into lower-order sequence sets: the lower and upper sequence sets. The lower sequence set, including Sq1-Sq3, is characterized by peritidal facies-dominated sequences and a progressive decrease in accommodation space, indicating a longer-term fall in sea level. In contrast, the upper sequence set (Sq4-Sq6) is characterized by subtidal facies-dominated sequences and a progressive increase in accommodation space, indicating a longer-term rise in sea level.
Increasing interests in hydrocarbon resources at depths have drawn greater attentions to the deeply-buried carbonate reservoirs in the Tarim Basin in China. In this study, the cyclic dolomite rocks of Upper Cambrian Lower Qiulitag Group from four outcrop sections in northwestern Tarim Basin were selected to investigate and evaluate the petrophysical properties in relation to depositional facies and cyclicity. The Lower Qiulitag Group includes ten lithofacies, which were deposited in intermediate to shallow subtidal, restricted shallow subtidal, intertidal, and supratidal environments on a carbonate ramp system. These lithofacies are vertically stacked into repeated shallowing-upward, meter-scale cycles which are further grouped into six third-order depositional sequences (Sq1 to Sq6). There are variable types of pore spaces in the Lower Qiulitag Group dolomite rocks, including interparticle, intraparticle, and fenestral pores of primary origin, inter crystal, and vuggy pores of late diagenetic modification. The porosity in the dolomites is generally facies-selective as that the microbially-originated thrombolites and stromatolites generally yield a relatively high porosity. In contrast, the high-energy ooidal grainstones generally have very low porosity. In this case, the microbialite-based peritidal cycles and peritidal cycle-dominated highstand (or regressive) successions have relatively high volumes of pore spaces, although highly fluctuating (or vertical inhomogeneous). Accordingly, the grainstone-based subtidal cycles and subtidal cycle-dominated transgressive successions generally yield extremely low porosity. This scenario indicates that porosity development and preservation in the thick dolomite successions are primarily controlled by depositional facies which were influenced by sea-level fluctuations of different orders and later diagenetic overprinting.
Temporal and spatial stability of the vegetation climate relationship is a basic ecological assumption for pollen-based quantitative inferences of past climate change and for predicting future vegetation. We explore this assumption for the Holocene in eastern continental Asia (China, Mongolia). Boosted regression trees (BRT) between fossil pollen taxa percentages (Abies, Artemisia, Betula, Chenopodiaceae, Cyperaceae, Ephedra, Picea, Pinus, Poaceae and Quercus) and climate model outputs of mean annual precipitation (P-ann) and mean temperature of the warmest month (Mt(wa)) for 9 and 6 ka (ka = thousand years before present) were set up and results compared to those obtained from relating modern pollen to modern climate. Overall, our results reveal only slight temporal differences in the pollen climate relationships. Our analyses suggest that the importance of P-ann compared with Mt(wa) for taxa distribution is higher today than it was at 6 ka and 9 ka. In particular, the relevance of P-ann for Picea and Pinus increases and has become the main determinant. This change in the climate tree pollen relationship parallels a widespread tree pollen decrease in north-central China and the eastern Tibetan Plateau. We assume that this is at least partly related to vegetation climate disequilibrium originating from human impact. Increased atmospheric CO2 concentration may have permitted the expansion of moisture-loving herb taxa (Cyperaceae and Poaceae) during the late Holocene into arid/semi-arid areas. We furthermore find that the pollen climate relationship between north-central China and the eastern Tibetan Plateau is generally similar, but that regional differences are larger than temporal differences. In summary, vegetation climate relationships in China are generally stable in space and time, and pollen-based climate reconstructions can be applied to the Holocene. Regional differences imply the calibration-set should be restricted spatially.
Recent global warming is pronounced in high-latitude regions (e.g. northern Asia), and will cause the vegetation to change. Future vegetation trends (e.g. the "arctic greening") will feed back into atmospheric circulation and the global climate system. Understanding the nature and causes of past vegetation changes is important for predicting the composition and distribution of future vegetation communities. Fossil pollen records from 468 sites in northern and eastern Asia were biomised at selected times between 40 cal ka bp and today. Biomes were also simulated using a climate-driven biome model and results from the two approaches compared in order to help understand the mechanisms behind the observed vegetation changes. The consistent biome results inferred by both approaches reveal that long-term and broad-scale vegetation patterns reflect global- to hemispheric-scale climate changes. Forest biomes increase around the beginning of the late deglaciation, become more widespread during the early and middle Holocene, and decrease in the late Holocene in fringe areas of the Asian Summer Monsoon. At the southern and southwestern margins of the taiga, forest increases in the early Holocene and shows notable species succession, which may have been caused by winter warming at ca. 7 cal ka bp. At the northeastern taiga margin (central Yakutia and northeastern Siberia), shrub expansion during the last deglaciation appears to prevent the permafrost from thawing and hinders the northward expansion of evergreen needle-leaved species until ca. 7 cal ka bp. The vegetation-climate disequilibrium during the early Holocene in the taiga-tundra transition zone suggests that projected climate warming will not cause a northward expansion of evergreen needle-leaved species.
The origin of Asian monsoons
(2020)
The Cenozoic inception and development of the Asian monsoons remain unclear and have generated much debate, as several hypotheses regarding circulation patterns at work in Asia during the Eocene have been proposed in the few last decades. These include (a) the existence of modern-like monsoons since the early Eocene; (b) that of a weak South Asian monsoon (SAM) and little to no East Asian monsoon (EAM); or (c) a prevalence of the Intertropical Convergence Zone (ITCZ) migrations, also referred to as Indonesian-Australian monsoon (I-AM). As SAM and EAM are supposed to have been triggered or enhanced primarily by Asian palaeogeographic changes, their possible inception in the very dynamic Eocene palaeogeographic context remains an open question, both in the modelling and field-based communities. We investigate here Eocene Asian climate conditions using the IPSL-CM5A2 (Sepulchre et al., 2019) earth system model and revised palaeogeographies. Our Eocene climate simulation yields atmospheric circulation patterns in Asia substantially different from modern conditions. A large high-pressure area is simulated over the Tethys ocean, which generates intense low tropospheric winds blowing southward along the western flank of the proto-Himalayan-Tibetan plateau (HTP) system. This low-level wind system blocks, to latitudes lower than 10 degrees N, the migration of humid and warm air masses coming from the Indian Ocean. This strongly contrasts with the modern SAM, during which equatorial air masses reach a latitude of 20-25 degrees N over India and southeastern China. Another specific feature of our Eocene simulation is the widespread subsidence taking place over northern India in the midtroposphere (around 5000 m), preventing deep convective updraught that would transport water vapour up to the condensation level. Both processes lead to the onset of a broad arid region located over northern India and over the HTP. More humid regions of high seasonality in precipitation encircle this arid area, due to the prevalence of the Intertropical Convergence Zone (ITCZ) migrations (or Indonesian-Australian monsoon, I-AM) rather than monsoons. Although the existence of this central arid region may partly result from the specifics of our simulation (model dependence and palaeogeographic uncertainties) and has yet to be confirmed by proxy records, most of the observational evidence for Eocene monsoons are located in the highly seasonal transition zone between the arid area and the more humid surroundings. We thus suggest that a zonal arid climate prevailed over Asia before the initiation of monsoons that most likely occurred following Eocene palaeogeographic changes. Our results also show that precipitation seasonality should be used with caution to infer the presence of a monsoonal circulation and that the collection of new data in this arid area is of paramount importance to allow the debate to move forward.
The origin of Asian monsoons
(2020)
The Cenozoic inception and development of the Asian monsoons remain unclear and have generated much debate, as several hypotheses regarding circulation patterns at work in Asia during the Eocene have been proposed in the few last decades. These include (a) the existence of modern-like monsoons since the early Eocene; (b) that of a weak South Asian monsoon (SAM) and little to no East Asian monsoon (EAM); or (c) a prevalence of the Intertropical Convergence Zone (ITCZ) migrations, also referred to as Indonesian-Australian monsoon (I-AM). As SAM and EAM are supposed to have been triggered or enhanced primarily by Asian palaeogeographic changes, their possible inception in the very dynamic Eocene palaeogeographic context remains an open question, both in the modelling and field-based communities. We investigate here Eocene Asian climate conditions using the IPSL-CM5A2 (Sepulchre et al., 2019) earth system model and revised palaeogeographies. Our Eocene climate simulation yields atmospheric circulation patterns in Asia substantially different from modern conditions. A large high-pressure area is simulated over the Tethys ocean, which generates intense low tropospheric winds blowing southward along the western flank of the proto-Himalayan-Tibetan plateau (HTP) system. This low-level wind system blocks, to latitudes lower than 10 degrees N, the migration of humid and warm air masses coming from the Indian Ocean. This strongly contrasts with the modern SAM, during which equatorial air masses reach a latitude of 20-25 degrees N over India and southeastern China. Another specific feature of our Eocene simulation is the widespread subsidence taking place over northern India in the midtroposphere (around 5000 m), preventing deep convective updraught that would transport water vapour up to the condensation level. Both processes lead to the onset of a broad arid region located over northern India and over the HTP. More humid regions of high seasonality in precipitation encircle this arid area, due to the prevalence of the Intertropical Convergence Zone (ITCZ) migrations (or Indonesian-Australian monsoon, I-AM) rather than monsoons. Although the existence of this central arid region may partly result from the specifics of our simulation (model dependence and palaeogeographic uncertainties) and has yet to be confirmed by proxy records, most of the observational evidence for Eocene monsoons are located in the highly seasonal transition zone between the arid area and the more humid surroundings. We thus suggest that a zonal arid climate prevailed over Asia before the initiation of monsoons that most likely occurred following Eocene palaeogeographic changes. Our results also show that precipitation seasonality should be used with caution to infer the presence of a monsoonal circulation and that the collection of new data in this arid area is of paramount importance to allow the debate to move forward.
Der zentralasiatische Naturraum, wie er sich uns heute präsentiert, ist das Ergebnis eines Zusammenwirkens vieler verschiedener Faktoren über Jahrmillionen hinweg. Im aktuellen Kontext des Klimawandels zeigt sich jedoch, wie stark sich Stoffflüsse auch kurzfristig ändern und dabei das Gesicht der Landschaft verwandeln können. Die Gobi-Wüste in der Inneren Mongolei (China), als Teil der gleichnamigen Trockenregionen Nordwestchinas, ist aufgrund der Ausgestaltung ihrer landschaftsprägenden Elemente sowie ihrer Landschaftsdynamik, im Zusammenhang mit der Lage zum Tibet-Plateau, in den Fokus der klimageschichtlichen Grundlagenforschung gerückt. Als großes Langzeitarchiv unterschiedlichster fluvialer, lakustriner und äolischer Sedimente stellt sie eine bedeutende Lokalität zur Rekonstruktion von lokalen und regionalen Stoffflüssen dar.. Andererseits ist die Gobi-Wüste zugleich auch eine bedeutende Quelle für den überregionalen Staubtransport, da sie aufgrund der klimatischen Bedingungen insbesondere der Erosion durch Ausblasung preisgegeben wird. Vor diesem Hintergrund erfolgten zwischen 2011 und 2014, im Rahmen des BMBF-Verbundprogramms WTZ Zentralasien – Monsundynamik & Geoökosysteme (Förderkennzeichen 03G0814), mehrere deutsch-chinesische Expeditionen in das Ejina-Becken (Innere Mongolei) und das Qilian Shan-Vorland. Im Zuge dieser Expeditionen wurden für eine Bestimmung potenzieller Sedimentquellen erstmals zahlreiche Oberflächenproben aus dem gesamten Einzugsgebiet des Heihe (schwarzer Fluss) gesammelt. Zudem wurden mit zwei Bohrungen im inneren des Ejina-Beckens, ergänzende Sedimentbohrkerne zum bestehenden Bohrkern D100 (siehe Wünnemann (2005)) abgeteuft, um weit reichende, ergänzende Informationen zur Landschaftsgeschichte und zum überregionalen Sedimenttransfer zu erhalten. Gegenstand und Ziel der vorliegenden Doktorarbeit ist die sedimentologisch-mineralogische Charakterisierung des Untersuchungsgebietes in Bezug auf potenzielle Sedimentquellen und Stoffflüsse des Ejina-Beckens sowie die Rekonstruktion der Ablagerungsgeschichte eines dort erbohrten, 19m langen Sedimentbohrkerns (GN100). Schwerpunkt ist hierbei die Klärung der Sedimentherkunft innerhalb des Bohrkerns sowie die Ausweisung von Herkunftssignalen und möglichen Sedimentquellen bzw. Sedimenttransportpfaden. Die methodische Herangehensweise basiert auf einem Multi-Proxy-Ansatz zur Charakterisierung der klastischen Sedimentfazies anhand von Geländebeobachtungen, lithologisch-granulometrischen und mineralogisch-geochemischen Analysen sowie statistischen Verfahren. Für die mineralogischen Untersuchungen der Sedimente wurde eine neue, rasterelektronenmikroskopische Methode zur automatisierten Partikelanalyse genutzt und den traditionellen Methoden gegenübergestellt. Die synoptische Betrachtung der granulometrischen, geochemischen und mineralogischen Befunde der Oberflächensedimente ergibt für das Untersuchungsgebiet ein logisches Kaskadenmodell mit immer wiederkehrenden Prozessbereichen und ähnlichen Prozesssignalen. Die umfangreichen granulometrischen Analysen deuten dabei auf abnehmende Korngrößen mit zunehmender Entfernung vom Qilian Shan hin und ermöglichen die Identifizierung von vier texturellen Signalen: den fluvialen Sanden, den Dünensanden, den Stillwassersedimenten und Stäuben. Diese Ergebnisse können als Interpretationsgrundlage für die Korngrößenanalysen des Bohrkerns genutzt werden. Somit ist es möglich, die Ablagerungsgeschichte der Bohrkernsedimente zu rekonstruieren und in Verbindung mit eigenen und literaturbasierten Datierungen in einen Gesamtkontext einzuhängen. Für das Untersuchungsgebiet werden somit vier Ablagerungsphasen ausgewiesen, die bis in die Zeit des letzten glazialen Maximums (LGM) zurückreichen. Während dieser Ablagerungsphasen kam es im Zuge unterschiedlicher Aktivitäts- und Stabilitätsphasen zu einer kontinuierlichen Progradation und Überprägung des Schwemmfächers. Eine besonders aktive Phase kann zwischen 8 ka und 4 ka BP festgestellt werden, während der es aufgrund zunehmender fluvialer Aktivitäten zu einer deutlich verstärkten Schwemmfächerdynamik gekommen zu sein scheint. In den Abschnitten davor und danach waren es vor allem äolische Prozesse, die zu einer Überprägung des Schwemmfächers geführt haben. Hinsichtlich der mineralogischen Herkunftssignale gibt es eine große Variabilität. Dies spiegelt die enorme Heterogenität der Geologie des Untersuchungsgebietes wider, wodurch die räumlichen Signale nicht sehr stark ausgeprägt sind. Dennoch, können für das Einzugsgebiet drei größere Bereiche deklariert werden, die als Herkunftsgebiet in Frage kommen. Das östliche Qilian Shan Vorland zeichnet sich dabei durch deutlich höhere Chloritgehalte als primäre Quelle für die Sedimente im Ejina-Becken aus. Sie unterscheiden sich insbesondere durch stark divergierende Chloritgehalte in der Tonmineral- und Gesamtmineralfraktion, was das östliche Qilian Shan Vorland als primäre Quelle für die Sedimente im Ejina-Becken auszeichnet. Dies steht in Zusammenhang mit den Grünschiefern, Ophioliten und Serpentiniten in diesem Bereich. Geochemisch deutet vor allem das Cr/Rb-Verhältnis eine große Variabilität innerhalb des Einzugsgebietes an. Auch hier ist es das östliche Vorland, welches aufgrund seines hohen Anteils an mafischen Gesteinen reich an Chromiten und Spinellen ist und sich somit vom restlichen Untersuchungsgebiet abhebt. Die zeitliche aber auch die generelle Variabilität der Sedimentherkunft lässt sich in den Bohrkernsedimenten nicht so deutlich nachzeichnen. Die mineralogisch-sedimentologischen Eigenschaften der erbohrten klastischen Sedimente zeugen zwar von zwischenzeitlichen Änderungen bei der Sedimentherkunft, diese sind jedoch nicht so deutlich ausgeprägt, wie es die Quellsignale in den Oberflächensedimenten vermuten lassen. Ein Grund dafür scheint die starke Vermischung unterschiedlichster Sedimente während des Transportes zu sein. Die Kombination der Korngrößenergebnisse mit den Befunden der Gesamt- und Schwermineralogie deuten darauf hin, dass es zwischenzeitlich eine Phase mit überwiegend äolischen Prozessen gegeben hat, die mit einem Sedimenteintrag aus dem westlichen Bei Shan in Verbindung stehen. Neben der Zunahme ultrastabiler Schwerminerale wie Zirkon und Granat und der Abnahme opaker Schwerminerale, weisen vor allem die heutigen Verhältnisse darauf hin. Der Vergleich der traditionellen Schwermineralanalyse mit der Computer-Controlled-Scanning-Electron-Microscopy (kurz: CCSEM), die eine automatisierte Partikelauswertung der Proben ermöglicht, zeigt den deutlichen Vorteil der modernen Analysemethode. Neben einem zeitlichen Vorteil, den man durch die automatisierte Abarbeitung der vorbereiteten Proben erlangen kann, steht vor allem die deutlich größere statistische Signifikanz des Ergebnisses im Vordergrund. Zudem können mit dieser Methode auch chemische Varietäten einiger Schwerminerale bestimmt werden, die eine noch feinere Klassifizierung und sicherere Aussagen zu einer möglichen Sedimentherkunft ermöglichen. Damit ergeben sich außerdem verbesserte Aussagen zu Zusammensetzungen und Entstehungsprozessen der abgelagerten Sedimente. Die Studie verdeutlicht, dass die Sedimentherkunft innerhalb des Untersuchungsgebietes sowie die ablaufenden Prozesse zum Teil stark von lokalen Gegebenheiten abhängen. Die Heterogenität der Geologie und die Größe des Einzugsgebietes sowie die daraus resultierende Komplexität der Sedimentgenese, machen exakte Zuordnungen zu klar definierten Sedimentquellen sehr schwer. Dennoch zeigen die Ergebnisse, dass die Sedimentzufuhr in das Ejina-Becken in erster Linie durch fluviale klastische Sedimente des Heihe aus dem Qilian Shan erfolgt sein muss. Die Untersuchungsergebnisse zeigen jedoch ebenso die Notwendigkeit einer ergänzenden Bearbeitung angrenzender Untersuchungsgebiete, wie beispielsweise den Gobi-Altai im Norden oder den Beishan im Westen, sowie die Verdichtung der Oberflächenbeprobung zur feineren Auflösung von lokalen Sedimentquellen.
Region ohne Richtung
(2023)
Welche Auswirkungen wird die aufziehende Großmächtekonkurrenz also auf die regionale Sicherheitsordnung haben? Der Beitrag nähert sich dieser Frage über die regionalen Bedingungsfaktoren, die den Rahmen für jegliche Ingerenz extraregionaler Mächte bilden: Die regionalen Sicherheitskomplexe in Lateinamerika und der Karibik, einschließlich der Regionalorganisationen und Regionalmächte, sowie der Einflusssphären und Anreizsysteme der Großmächte. Am Ende wagt der Beitrag einen Ausblick auf die Entwicklung der lateinamerikanischen Sicherheitspolitik im Angesicht der Geopolitik der Großmächte. Die hier vorgestellte Kernthese wagt ein strukturelles und deshalb wenig alarmistisches Argument: Die Großmächtekonkurrenz wird die bestehende Fragmentierung der regionalen Sicherheitsordnung weiter vertiefen, doch wird die Region gleichzeitig nicht substanziell an Agency gegenüber den Großmächten verlieren. Der Schlüssel hierzu ist die außenpolitische Maxime der „gebundenen Äquidistanz“, die Dependenzen diversifiziert und damit nicht als Widerspruch, sondern als Positivsummenspiel versteht.
Sediments of Lake Donggi Cona on the northeastern Tibetan Plateau were studied to infer changes in the lacustrine depositional environment, related to climatic and non-climatic changes during the last 19 kyr. The lake today fills a 30x8 km big and 95 m deep tectonic basin, associated with the Kunlun Fault. The study was conducted on a sediment-core transect through the lake basin, in order to gain a complete picture of spatio-temporal environmental change. The recovered sediments are partly finely laminated and are composed of calcareous muds with variable amounts of carbonate micrite, organic matter, detrital silt and clay. On the basis of sedimentological, geochemical, and mineralogical data up to five lithological units (LU) can be distinguished that document distinct stages in the development of the lake system.
The onset of the lowermost LU with lacustrine muds above basal sands indicates that lake level was at least 39 m below the present level and started to rise after 19 ka, possibly in response to regional deglaciation. At this time, the lacustrine environment was characterized by detrital sediment influx and the deposition of siliciclastic sediment. In two sediment cores, upward grain-size coarsening documents a lake-level fall after 13 cal ka BP, possibly associated with the late-glacial Younger Dryas stadial. From 11.5 to 4.3 cal ka BP, grain-size fining in sediment cores from the profundal coring sites and the onset of lacustrine deposition at a litoral core site (2 m water depth) in a recent marginal bay of Donggi Cona document lake-level rise during the early to mid-Holocene to at least modern level. In addition, high biological productivity and pronounced precipitation of carbonate micrites are consistent with warm and moist climate conditions related to an enhanced influence of summer monsoon. At 4.3 cal ka BP the lake system shifted from an aragonite- to a calcite-dominated system, indicating a change towards a fully open hydrological lake system. The younger clay-rich sediments are moreover non-laminated and lack any diagenetic sulphides, pointing to fully ventilated conditions, and the prevailing absence of lake stratification. This turning point in lake history could imply either a threshold response to insolation-forced climate cooling or a response to a non-climatic trigger, such as an erosional event or a tectonic pulse that induced a strong earthquake, which is difficult to decide from our data base.