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Jurgen Kurths - One of the best experts on this subject based on the ideXlab platform.
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complex network analysis of time series
EPL, 2016Co-Authors: Zhongke Gao, Jurgen Kurths, Michael SmallAbstract:Revealing complicated behaviors from time series constitutes a fundamental problem of continuing interest and it has attracted a great deal of attention from a wide variety of fields on account of its significant importance. The past decade has witnessed a rapid development of complex network studies, which allow to characterize many types of systems in nature and technology that contain a large number of components interacting with each other in a complicated manner. Recently, the complex network theory has been incorporated into the analysis of time series and fruitful achievements have been obtained. Complex network analysis of time series opens up new venues to address interdisciplinary challenges in Climate Dynamics, multiphase flow, brain functions, ECG Dynamics, economics and traffic systems.
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complex networks in Climate Dynamics comparing linear and nonlinear network construction methods
European Physical Journal-special Topics, 2009Co-Authors: Norbert Marwan, Jonathan F Donges, Yong Zou, Jurgen KurthsAbstract:Complex network theory provides a powerful framework to statistically investigate the topology of local and non-local statistical interrelationships, i.e. teleconnections, in the Climate system. Climate networks constructed from the same global climatological data set using the linear Pearson correlation coefficient or the nonlinear mutual information as a measure of dynamical similarity between regions, are compared systematically on local, mesoscopic and global topological scales. A high degree of similarity is observed on the local and mesoscopic topological scales for surface air temperature fields taken from AOGCM and reanalysis data sets. We find larger differences on the global scale, particularly in the betweenness centrality field. The global scale view on Climate networks obtained using mutual information offers promising new perspectives for detecting network structures based on nonlinear physical processes in the Climate system.
Brian M Chase - One of the best experts on this subject based on the ideXlab platform.
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vegetation and Climate Dynamics during the last glacial period in the fynbos afrotemperate forest ecotone southern cape south africa
Quaternary International, 2016Co-Authors: Lynne J Quick, Michael E Meadows, Mark D Bateman, Kelly L Kirsten, Roland Mausbacher, Torsten Haberzettl, Brian M ChaseAbstract:Abstract Despite the southern Cape's great climatic and botanical significance (occupying the transition between the temperate and subtropical circulation systems and forming part of a global biodiversity hotspot), palaeoenvironmental data for this region of southern Africa is limited. This study presents pollen, charcoal and sedimentological data preserved in the Vankervelsvlei wetland, situated in the modern year-round rainfall zone at the ecotone between the Fynbos and Afrotemperate Forest biomes. Combining optically stimulated luminescence and radiocarbon dating techniques, it was possible to establish a chronology for a sediment sequence spanning the last 140,000 years, the longest record yet produced in the region. The data suggest that MIS 5d was relatively warmer (low fynbos pollen percentages and Pentzia-type pollen) than later MIS 5, MIS 4 and most of MIS 3 (∼96–37 ka), which were characterised by decreased temperatures (dominance of ericaceous fynbos). The pollen data indicate a complex response to the change from interglacial to glacial conditions, and suggest an important threshold is crossed in regional ecological Dynamics. We postulate that during MIS 5d increased summer rainfall under warmer conditions may have offset increased potential evapotranspiration, allowing for the development of more extensive forests. During its early stages of development Vankervelsvlei was more open (increased aquatics and coarse sediment), trapping more longer-distance pollen (Podocarpus). As the mire became more closed, local elements dominated; a succession that is reflected in significant changes in the pollen assemblage, as Podocarpus remains only in trace percentages, but pollen of Canthium and Morella, which occupy nearly identical climatic niches as Podocarpus, increase in abundance. It is suggested that drought stress remains limited during the last glacial period as a result of reduced temperatures, compensating for what may have been a more seasonal winter-dominated rainfall regime, and that changes in the pollen record relate to vegetation succession and the development of the wetland rather than to major changes in moisture availability. Due to the virtual absence of palaeodata from the southern Cape covering MIS 5 to MIS 3, the establishment of this record provides an important contribution to the overall palaeoenvironmental history of the region.
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late glacial interhemispheric Climate Dynamics revealed in south african hyrax middens
Geology, 2011Co-Authors: Lynne J Quick, Michael E Meadows, Brian M Chase, Louis Scott, David S G Thomas, Paula J ReimerAbstract:Our ability to identify the timing and extent of past major Climate fluctuations is central to understanding changes in the global Climate system. Of the events that have occurred in recent geological time, the Younger Dryas (YD, 13–11.5 ka), an abrupt return to near-glacial conditions during the last glacial–interglacial transition (ca. 18–11.5 ka), is one of the most widely reported. While this event is apparent throughout the Northern Hemisphere ([Peteet, 1995][1]), evidence for its occurrence in the Southern Hemisphere remains equivocal due to a lack of well-dated terrestrial records. Here we report high-resolution stable carbon and nitrogen isotope records obtained from a rock hyrax midden, revealing the first unequivocal terrestrial manifestation of the YD from the southern African subtropics. These results provide key evidence for the relative influence of the YD, and suggest that a subtropical-temperate transition zone existed along the oceanic Subtropical Front (∼41°S) across the Southern Hemisphere, with the Northern Hemisphere exerting a strong influence on all but the higher latitudes of the Southern Hemisphere after the Heinrich Stadial 1 (15 ka). [1]: #ref-22
Raymond T Pierrehumbert - One of the best experts on this subject based on the ideXlab platform.
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the phase curve signature of condensible water rich atmospheres on slowly rotating tidally locked exoplanets
arXiv: Earth and Planetary Astrophysics, 2020Co-Authors: Feng Ding, Raymond T PierrehumbertAbstract:We use an idealized three-dimensional general circulation model to study condensible-rich atmospheres with an ineffective cold trap on slowly rotating tidally locked terrestrial planets. In particular, we show the Climate Dynamics in a thin and temperate atmosphere with condensible water vapor. The similarities between our thin and temperate atmosphere and the warm and thick atmosphere approaching the water vapor runaway greenhouse in previous works are discussed, including the reversal of the thermal emission between the day and night hemispheres. Different from the transit spectroscopy of water vapor that depends on the absolute amount of atmospheric water vapor, the contrast between the dayside and nightside thermal emission provides information regarding the relative ratio of water vapor to the background atmosphere as well as the atmospheric pressure near the substellar tropopause and the emission level on the nightside on potentially habitable worlds.
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Climate Dynamics of a hard snowball earth
Journal of Geophysical Research, 2005Co-Authors: Raymond T PierrehumbertAbstract:[1] The problem of deglaciating a globally ice-covered (“hard snowball”) Earth is examined using a series of general circulation model simulations. The aim is to determine the amount of CO2 that must be accumulated in the atmosphere in order to trigger deglaciation. Prior treatments of this problem have been limited to energy balance models, which are incapable of treating certain crucial physical processes that turn out to strongly affect the conditions under which deglaciation can occur. CO2 concentrations up to .2 bars are considered in the general circulation model simulations, and even at such high CO2 content the model radiation code is found to perform well in comparison with codes explicitly designed for high CO2. In contrast to prevailing expectations, the hard snowball Earth is found to be nearly 30 K short of deglaciation, even at .2 bars. The very cold Climates arise from a combination of the extreme seasonal and diurnal cycle, lapse rate effects, snow cover, and weak cloud effects. Several aspects of the atmospheric Dynamics are examined in detail. The simulations indicate that the standard scenario, wherein snowball termination occurs after a few tenths of a bar of CO2 has built up following cessation of weathering, is problematic. However, the Climate was found to be sensitive to details of a number of parameterized physical processes, notably clouds and heat transfer through the stable boundary layer. It is not out of the question that other parameterization suites might permit deglaciation. The results should not be construed as meaning that the hard snowball state could not have occurred, but only that deglaciation requires the operation of as-yet undiscovered processes that would enhance the Climate sensitivity. A brief survey of some of the possibilities is provided.
Pavel E Tarasov - One of the best experts on this subject based on the ideXlab platform.
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holocene vegetation and Climate Dynamics of ne china based on the pollen record from sihailongwan maar lake
Quaternary Science Reviews, 2015Co-Authors: Martina Stebich, Kira Rehfeld, Frank Schlutz, Pavel E Tarasov, Jens MingramAbstract:Abstract High-resolution palynological analysis on annually laminated sediments of Sihailongwan Maar Lake (SHL) provides new insights into the Holocene vegetation and Climate Dynamics of NE China. The robust chronology of the presented record is based on varve counting and AMS radiocarbon dates from terrestrial plant macro-remains. In addition to the qualitative interpretation of the pollen data, we provide quantitative reconstructions of vegetation and Climate based on the method of biomization and weighted averaging partial least squares regression (WA-PLS) technique, respectively. Power spectra were computed to investigate the frequency domain distribution of proxy signals and potential natural periodicities. Pollen assemblages, pollen-derived biome scores and Climate variables as well as the cyclicity pattern indicate that NE China experienced significant changes in temperature and moisture conditions during the Holocene. Within the earliest phase of the Holocene, a large-scale reorganization of vegetation occurred, reflecting the reconstructed shift towards higher temperatures and precipitation values and the initial Holocene strengthening and northward expansion of the East Asian summer monsoon (EASM). Afterwards, summer temperatures remain at a high level, whereas the reconstructed precipitation shows an increasing trend until approximately 4000 cal. yr BP. Since 3500 cal. yr BP, temperature and precipitation values decline, indicating moderate cooling and weakening of the EASM. A distinct periodicity of 550–600 years and evidence of a Mid–Holocene transition from a temperature-triggered to a predominantly moisture-triggered Climate regime are derived from the power spectra analysis. The results obtained from SHL are largely consistent with other palaeoenvironmental records from NE China, substantiating the regional nature of the reconstructed vegetation and Climate patterns. However, the reconstructed Climate changes contrast with the moisture evolution recorded in S China and the mid-latitude (semi-)arid regions of N China. Whereas a clear insolation-related trend of monsoon intensity over the Holocene is lacking from the SHL record, variations in the coupled atmosphere-Pacific Ocean system can largely explain the reconstructed changes in NE China.
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holocene environments and Climate in the mongolian altai reconstructed from the hoton nur pollen and diatom records a step towards better understanding Climate Dynamics in central asia
Quaternary Science Reviews, 2009Co-Authors: Natalia Rudaya, Andrei Andreev, Pavel E Tarasov, Nadezhda I Dorofeyuk, Nadia Solovieva, I A Kalugin, Andrei Daryin, Bernhard Diekmann, Frank Riedel, Narantsetseg TserendashAbstract:Abstract This study presents the results of the palynological and diatom analyses of the sediment core recovered in Hoton-Nur Lake (48°37′18″N, 88°20′45″E, 2083 m) in 2004. Quantitative reconstruction of the Holocene vegetation and Climate Dynamics in the semiarid Mongolian Altai suggests that boreal woodland replaced the primarily open landscape of northwestern Mongolia at about 10 kyr BP (1 kyr = 1000 cal yr) in response to a noticeable increase in precipitation from 200–250 mm/yr to 450–550 mm/yr. A decline of the forest vegetation and a return to a predominance of open vegetation types occurred after 5 kyr BP when precipitation sums decreased to 250–300 mm/yr. Prior to 11.5 kyr BP diatom concentrations are relatively low and the lake is dominated by planktonic Cyclotella and small Fragilariaceae, suggesting the existence of a relatively deep and oligotrophic/mesotrophic lake. The great abundance of Staurosirella pinnata from the beginning of the record until 10.7 kyr BP might imply intensified erosion processes in the catchment and this is fully consistent with the presence of scarce and dry vegetation and the generally arid Climate during this period. From about 10.7 kyr BP, more planktonic diatom taxa appeared and increased in abundance, indicating that the lake became more productive as diatom concentration increased. This change correlates well with the development of boreal woodland in the catchment. Decrease in precipitation and changes in the vegetation towards steppe are reflected by the rapid increase in Aulacoseira distans from about 5 kyr BP. The Holocene pollen and diatom records do not indicate soil and vegetation cover disturbances by the anthropogenic activities, implying that the main transformations of the regional vegetation occurred as a result of the natural Climate change. Our reconstruction is in agreement with the paleomonsoon records from China, demonstrating an abrupt strengthening of the summer monsoon at 12 kyr BP and an associated increase in precipitation and in lake levels between 11 and 8 kyr BP, followed by the stepwise attenuation of the monsoon circulation and Climate aridization towards the modern level. The records from the neighboring areas of Kazakhstan and Russia, situated west and north of Hoton-Nur, demonstrate spatially and temporally different Holocene vegetation and Climate histories, indicating that the Altai Mountains as a Climate boundary are of pivotal importance for the Holocene environmental and, possibly, habitation history of Central Asia.
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vegetation and Climate Dynamics during the holocene and eemian interglacials derived from lake baikal pollen records
Palaeogeography Palaeoclimatology Palaeoecology, 2007Co-Authors: Pavel E Tarasov, E V Bezrukova, Eugene B Karabanov, Takeshi Nakagawa, Mayke Wagner, N V Kulagina, P P Letunova, A A Abzaeva, Wojciech GranoszewskiAbstract:Abstract The last interglacial (LI) and Holocene changes in annual precipitation ( P ann ), the mean temperature of the warmest ( T w ) and coldest ( T c ) month and the moisture index ( α ) were reconstructed from continuous pollen records from Lake Baikal. The Holocene core (52°31′N, 106°09′E) presented in this study was recovered from a depth of 355 m in the 25-km wide underwater Buguldeika saddle separating the southern sub-basin of Lake Baikal from its central sub-basin. The biome reconstruction shows that tundra and steppe biomes have highest scores during ca. 15,000–13,300 cal. years B.P. and that taiga becomes a dominant vegetation type after ca. 13,300 cal. years B.P. Our quantitative reconstruction indicates an onset of relatively warm and wet conditions soon after ca. 10,000 cal. years B.P. The warmest and wettest Climate with T w ∼ 16 °C, P ann ∼ 480 mm and α ∼ 0.9–1 has been reconstructed for ca. 9000–7000 cal. years B.P. In the Lake Baikal region this interval is characterized by the appearance and spread of hunter communities (Kitoi culture). Consistently a hiatus in the regional archaeological record (4900–4200 years B.C. or 6850–6150 cal. years B.P.) coincides with the interval of a major Climate deterioration which followed the ‘climatic optimum’. An attempt to find a relationship between the archaeological record and a spread of steppe and meadow communities in the Lake Baikal region demonstrates that despite a long habitation of the area the human impact on vegetation was local rather than regional and likely did not affect the pollen record from Lake Baikal. The reconstructed peaks in the steppe biome scores during the last 9000 years are consistent with short (one to five hundred year) episodes of weak Pacific (summer) monsoon supporting our interpretation that the Holocene vegetation changes around Lake Baikal are associated with large-scale circulation processes controlling regional water balance rather than with human activities. Thus, our study proves the suitability of Lake Baikal pollen data for the reconstruction of natural vegetation and Climate Dynamics through the whole period from the onset of the LI to the present. Comparison of the recent and the last interglacial suggests that the Holocene ‘climatic optimum’ was less pronounced (e.g. lower summer and winter temperatures and annual precipitation sums) than that of the LI. On the other hand, pollen records demonstrate that the Holocene ‘forest phase’ already lasts some thousand years longer than that of the LI. The interglacial vegetation Dynamics derived from the Lake Baikal pollen records can be satisfactorily explained by reconstructed changes in summer and winter temperatures and in available moisture. The interglacial vegetation around Lake Baikal is dominated by the boreal forests, which are associated with a generally warm and wet Climate. The high sea level associated with decreased ice volume appears to have had a greater impact on the Siberian environments during the last and the recent interglacial than the direct effect of lower-than-present winter insolation. Reconstructed changes in the winter temperature correlate well with changes in the sea level and global ice volume, while the summer temperatures derived from the Lake Baikal pollen records track changes in the summer insolation.
Francesca Pongiglione - One of the best experts on this subject based on the ideXlab platform.
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the influence of causal knowledge on the willingness to change attitude towards Climate change results from an empirical study
International Journal of Science Education, 2017Co-Authors: Giulia Tasquier, Francesca PongiglioneAbstract:ABSTRACTClimate change is one of the significant global challenges currently facing humanity. Even though its seriousness seems to be common knowledge among the public, the reaction of individuals to it has been slow and uncertain. Many studies assert that simply knowing about Climate change is not enough to generate people’s behavioural response. They claim, indeed, that in some cases scientific literacy can even obstruct behavioural response instead. However, recent surveys show a rather poor understanding of Climate Dynamics and argue that lack of knowledge about causal relationships within Climate Dynamics can hinder behavioural response, since the individual is not able to understand his/her role as causal agent and therefore doesn’t know how to take proper action. This study starts from the hypothesis that scientific knowledge focused on clarifying Climate Dynamics can make people understand not only Dynamics themselves, but also their interactive relationship with the environment. Teaching material...
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the influence of causal knowledge on the willingness to change attitude towards Climate change results from an empirical study
International Journal of Science Education, 2017Co-Authors: Giulia Tasquier, Francesca PongiglioneAbstract:ABSTRACTClimate change is one of the significant global challenges currently facing humanity. Even though its seriousness seems to be common knowledge among the public, the reaction of individuals to it has been slow and uncertain. Many studies assert that simply knowing about Climate change is not enough to generate people’s behavioural response. They claim, indeed, that in some cases scientific literacy can even obstruct behavioural response instead. However, recent surveys show a rather poor understanding of Climate Dynamics and argue that lack of knowledge about causal relationships within Climate Dynamics can hinder behavioural response, since the individual is not able to understand his/her role as causal agent and therefore doesn’t know how to take proper action. This study starts from the hypothesis that scientific knowledge focused on clarifying Climate Dynamics can make people understand not only Dynamics themselves, but also their interactive relationship with the environment. Teaching material...