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[en] Ice cores from Greenland give testimony of a highly variable climate during the last glacial period. Dramatic climate warmings of 15 to 25 deg. C for the annual average temperature in less than a human lifetime have been documented. Several questions arise: Why is the Holocene so stable? Is climatic instability only a property of glacial periods? What is the mechanism behind the sudden climate changes? Are the increased temperatures in the past century man-made? And what happens in the future? The ice core community tries to attack some of these problems. The NGRIP ice core currently being drilled is analysed in very high detail, allowing for a very precise dating of climate events. It will be possible to study some of the fast changes on a year by year basis and from this we expect to find clues to the sequence of events during rapid changes. New techniques are hoped to allow for detection of annual layers as far back as 100,000 years and thus a much improved time scale over past climate changes. It is also hoped to find ice from the Eemian period. If the Eemian layers confirm the GRIP sequence, the Eemian was actually climatically unstable just as the glacial period. This would mean that the stability of the Holocene is unique. It would also mean, that if human made global warming indeed occurs, we could jeopardize the Holocene stability and create an unstable 'Eemian situation' which ultimately could start an ice age. Currenlty mankind is changing the composition of the atmosphere. Ice cores document significant increases in greenhouse gases, and due to increased emissions of sulfuric and nitric acid from fossil fuel burning, combustion engines and agriculture, modern Greenland snow is 3 - 5 times more acidic than pre-industrial snow (Mayewski et al., 1986). However, the magnitude and abruptness of the temperature changes of the past century do not exceed the magnitude of natural variability. It is from the ice core perspective thus not possible to attribute the warming of the past century solely to the influence of mankind. The climate changes recorded by meteorological observations since 1875 are not unique in climate history. Taking into account that the period around 1875 appears to have been one of the coldest during the Holocene makes it even more difficult. Although the present situation is different from the past, we still need to understand past climatic changes in order to not only assess the effects of human activity but also to make better predictions of possible future natural climatic changes. The ice core community will continue to try to unravel the story of plast climate changes - this is our challenge. (LN)
[en] This book presents the results of physics, biology, environment and chemistry experts discussions concerning the climatic change. What do we know from the passed climates? Can we forecast those of the next ten years? What is the part of the human activities in this evolution? What can we do and what must we do? (A.L.B.)
[en] While the majority of ice core investigations have been undertaken in the polar regions, a few ice cores recovered from carefully selected high altitude/mid-to-low latitude glaciers have also provided valuable records of climate variability in these regions. A regional array of high resolution, multi-parameter ice core records developed from temperate and tropical regions of the globe can be used to document regional climate and environmental change in the latitudes which are home to the vase majority of the Earth's human population. In addition, these records can be directly compared with ice core records available from the polar regions and can therefore expand our understanding of inter-hemispheric dynamics of past climate changes. The main objectives of our paleoclimate research in the Tien Shan mountains of middle Asia combine the development of detailed paleoenvironmental records via the physical and chemical analysis of ice cores with the analysis of modern meteorological and hydrological data. The first step in this research was the collection of ice cores from the accumulation zone of the Inylchek Glacier and the collection of meteorological data from a variety of stations throughout the Tien Shan. The research effort described in this report was part of a collaborative effort with the United State Geological Survey's (USGS) Global Environmental Research Program which began studying radionuclide deposition in mid-latitude glaciers in 1995
[en] Tree ring is a kind of natural archives, on which the isotopic analysis is important to study global climate and environmental change. The authors mainly provide a comprehensive introduction to the fractionation models of carbon, hydrogen and oxygen isotope in plants, their research technique and the extract methods from cellulose. That results show isotopic tracer can record the message of climatic variation and has become a powerful tool for paleoclimate reconstruction and for the modern environment changing research. Especially studying on PAGES. the cellulose isotopic analyses of imbedded old tree ring have become the mainly quantitative means of environmental evolvement. In addition, China is a typical monsoon country, research in tree ring stable isotope seasonal variation can give a lot of important information on that. Up to now, the research techniques and works on tree ring in China are still in its earlier stage, and remain many limitations. It needs further accumulate basic research materials, intensity regional contrast and intercross studies on relative subjects
[en] The results of a simulated CO2 (C) and a global ice volume (V) time series, derived from a simple relaxation model of the glacial-interglacial cycles (García-Olivares and Herrero, 2013), have been analyzed using linear and non-linear techniques to evaluate the ability of the model on simulating the dynamics embedded on the climate system. On a first approximation, we have compared simulated time series with the corresponding paleoclimatic reconstructions, obtaining correlations of 0.88 between proxy-record δ18O (Lisiecki and Raymo, 2005) and simulated V, and 0.79 between reconstructed atmospheric CO2 concentration (Petit et al., 1999; Indermuhle et al., 2000; Monnin et al., 2001; Siegenthaler et al., 2005; Luthi et al., 2008) and simulated C. Spectral analysis using Fourier transform and continuous wavelet transform are useful tools to quantify the performance of a model for reproducing the dynamics embedded in reconstructed time series. The analysis shows that the model reproduces closely the dynamics embedded in the ice volume time series, but the coherence between the simulated and reconstructed CO2 is only sporadic, indicating that both time series do not follow the same dynamical behaviour, although in the deglacial periods the two carbon series become dynamically close. The analysis reinforces the hypothesis that some specific mechanisms included in the model are able to closely reproduce the glacial-interglacial oscillations and thus suggests which specific mechanisms should be more seriously investigated in the climate system. These techniques may be applied to other climatic time series to quantify the performance of a model simulating the dynamics of the climate system.
[es]Las series simuladas de CO2 (C) y de volumen de hielo global (V) derivadas de un modelo de relajación de ciclos glaciares-interglaciares (García-Olivares y Herrero, 2013) han sido analizadas usando técnicas lineales y no-lineales para evaluar la habilidad del modelos en simular la dinámica del sistema climático. En una primera aproximación, hemos comparado las series simuladas con su correspondiente serie experimental, obteniendo correlaciones de 0.88 entre el proxy δ18O (Lisiecki y Raymo, 2005) y la simulación V, y 0.79 entre la concentración de CO2 atmosférico (Petit et al., 1999; Indermuhle et al., 2000; Monnin et al., 2001; Siegenthaler et al., 2005; Luthi et al., 2008) y la correspondiente serie, C. El análisis espectral usando la transformada de Fourier y la transformada continua de wavelet resulta útil para cuantificar el rendimiento de un modelo reproduciendo la dinámica incluida dentro de una serie experimental. El análisis muestra que el modelo reproduce adecuadamente la dinámica de la serie de volumen de hielo, pero la coherencia entre la serie simulada y la experimental de CO2 es únicamente esporádica, indicando que ambas series no tienen el mismo comportamiento dinámico, pese a que en los periodos de desglaciación las dos series de carbono tienen un comportamiento muy similar. El análisis refuerza la hipótesis que ciertos mecanismos específicos incluidos en el modelo son capaces de reproducir adecuadamente las oscilaciones glaciares-interglaciares. Estas técnicas pueden aplicarse a otras series climáticas para cuantificar el rendimiento de un modelo simulando la dinámica interna del sistema climático.