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Temperature Reconstruction (temperature + reconstruction)
Selected AbstractsTemperature reconstructions and comparisons with instrumental data from a tree-ring network for the European AlpsINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 11 2005David Frank Abstract Ring-width and maximum latewood density data from a network of high-elevation sites distributed across the European Alps are used to reconstruct regional temperatures. The network integrates 53 ring-width and 31 density chronologies from stands of four species all located above 1500 m a.s.l. The development and basic climatic response patterns of this network are described elsewhere (Frank and Esper, 2005). The common temperature signal over the study region allowed regional reconstructions to be developed using principal component regression models for average June,August (1600,1988) and April,September (1650,1987) temperatures from ring-width and density records, respectively. Similar climatic histories are derived for both seasons, but with the ring-width and density-based reconstructions seemingly weighted toward carrying more of their variance in the lower and higher frequency domains, respectively. Distinct warm decades are the 1940s, 1860s, 1800s, 1730s, 1660s and the 1610s, and cold decades, the 1910s, 1810s, 1710s, 1700s and the 1690s. Because of the model fitting and the shorter time spans involved, comparisons between the reconstructions with high-elevation instrumental data during the majority of the 1864,1972 calibration period show good agreement. Yet, prior to this period, from which only a few low elevation temperature records are available, a trend divergence between tree-ring and instrumental records is observed. We present evidence that this divergence may be explained by the ring-width data carrying more of an annual rather than warm-season signal in the lower frequency domain. Other factors such as noise, tree-ring standardization, or the more uncertain nature of low-frequency trends in early instrumental records and their homogenization, might help explain this divergence as well. Copyright © 2005 Royal Meteorological Society. [source] Spring,summer temperature reconstruction in western Norway 1734,2003: a data-synthesis approachINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 15 2003P. Ø. Nordli Abstract A series of spring,summer (April,August) temperatures was reconstructed for the period 1734,1923 for western Norway based on multi-proxy data. For the period 1734,1842 the long-term variations were based on terminal moraines in front of two southern Norwegian glaciers, whereas the annual variations were based on grain-harvest data extracted from farmers' diaries. For the period 1843,1867 the spring,summer temperatures were reconstructed solely from diaries overlapping instrumental observations. All the results were incorporated into one series for the period 1734,2003 to form the Vestlandet composite series. The reconstruction method using terminal-moraine sequences was tested against the modern instrumental Bergen series for the periods of moraine formations in front of the glaciers. The agreement with the instrumental series was good, with the mean difference for all periods being only 0.2 °C. Analyses of decadal variations in western Norway revealed three periods of low spring,summer temperatures: around 1740, in the first decade of the 19th century, and in the 1830s. These periods are well known from historic records as periods of starvation, during which the use of bark bread became common. Copyright © 2003 Royal Meteorological Society [source] Millennia-long tree-ring records from Tasmania and New Zealand: a basis for modelling climate variability and forcing, past, present and future,JOURNAL OF QUATERNARY SCIENCE, Issue 7 2006Edward R. Cook Abstract Progress in the development of millennia-long tree-ring chronologies from Australia and New Zealand is reviewed from the perspective of modelling long-term climate variability there. Three tree species have proved successful in this regard: Huon pine (Lagarostrobos franklinii) from Tasmania, silver pine (L. colensoi) from the South Island of New Zealand, and kauri (Agathis australis) from the North Island of New Zealand. Each of these species is very long-lived and produces abundant quantities of well-preserved wood for extending their tree-ring chronologies back several millennia into the past. The growth patterns on these chronologies strongly correlate with both local and regional warm-season temperature changes over significant areas of the Southern Hemisphere (especially Huon and silver pine) and to ENSO variability emanating from the equatorial Pacific region (especially kauri). In addition, there is evidence for significant, band-limited, multi-decadal and centennial timescale variability in the warm-season temperature reconstruction based on Huon pine tree rings that may be related to slowly varying changes in ocean circulation dynamics in the southern Indian Ocean. This suggests the possibility of long-term climate predictability there. Copyright © 2006 John Wiley & Sons, Ltd. [source] Time series modelling of two millennia of northern hemisphere temperatures: long memory or shifting trends?JOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES A (STATISTICS IN SOCIETY), Issue 1 2007Terence C. Mills Summary., The time series properties of the temperature reconstruction of Moberg and co-workers are analysed. It is found that the record appears to exhibit long memory characteristics that can be modelled by an autoregressive fractionally integrated moving average process that is both stationary and mean reverting, so that forecasts will eventually return to a constant underlying level. Recent research has suggested that long memory and shifts in level and trend may be confused with each other, and fitting models with slowly changing trends is found to remove the evidence of long memory. Discriminating between the two models is difficult, however, and the strikingly different forecasts that are implied by the two models point towards some intriguing research questions concerning the stochastic process driving this temperature reconstruction. [source] Interglacial Chironomidae (Diptera) from Thule, Northwest Greenland: matching modern analogues to fossil assemblagesBOREAS, Issue 4 2003KLAUS PETER BRODERSEN An analysis of subfossil insect remains (Diptera, Chironomidae) from an interglacial site at Narsaarsuk near Thule Air Base, NW Greenland, was undertaken to complement our understanding of last interglacial environments in the Arctic by analogue matching to modern chironomid assemblages. The subfossil larval midge head capsules were well preserved and 82% of the chironomid remains were identified as eight different extant chironomid taxa. The assemblage was dominated by the lotic Diamesa (43.8%), a number of lentic taxa (Hydrobaenus, Psectrocladius, Cricotopus/Orthocladius) and a few semi-aquatic taxa (Smittia, Chaetocladius). A single black fly head capsule (Diptera, Simuliidae) was registered. The interglacial sample was compared to subfossil chironomid assemblages from 42 lakes in West Greenland, two glacier lakes (with and without river influence) and a quantitative zoobenthos study from Narsaq Elv. Similarity analysis, analogue matching and multidimensional scaling suggest a lotic, cold, glacier-fed interglacial palaeo-biotope. Quantitative temperature reconstruction was not possible owing to a high dissimilarity to modern lentic chironomid assemblages from West Greenland. However, the simple numerical methods convincingly managed to reflect an interglacial river and stream environment, which can be difficult to document from other palaeoecological data. [source] | ||||||||||