Time filter

Source Type

Kern Z.,Institute for Geological and Geochemical Research | Leuenberger M.,University of Bern | Leuenberger M.,Oeschger Center for Climate Change Research
Global and Planetary Change | Year: 2013

A recent study relying purely on statistical analysis of relatively short time series suggested substantial re-thinking of the traditional view about causality explaining the detected rising trend of atmospheric CO2 (atmCO2) concentrations. If these results are well-justified then they should surely compel a fundamental scientific shift in paradigms regarding both atmospheric greenhouse warming mechanism and global carbon cycle. However, the presented work suffers from serious logical deficiencies such as, 1) what could be the sink for fossil fuel CO2 emissions, if neither the atmosphere nor the ocean - as suggested by the authors - plays a role? 2) What is the alternative explanation for ocean acidification if the ocean is a net source of CO2 to the atmosphere? Probably the most provocative point of the commented study is that anthropogenic emissions have little influence on atmCO2 concentrations. The authors have obviously ignored the reconstructed and directly measured carbon isotopic trends of atmCO2 (both δ13C, and radiocarbon dilution) and the declining O2/N2 ratio, although these parameters provide solid evidence that fossil fuel combustion is the major source of atmCO2 increase throughout the Industrial Era. © 2013 Elsevier B.V. Source

Takacs K.,Eotvos Lorand University | Kern Z.,Institute for Geological and Geochemical Research | Kern Z.,University of Bern | Nagy B.,Eotvos Lorand University
Quaternary International | Year: 2013

Anthropogenic effects on rivers, including engineering regulation, hydropower usage, and water pollution, not only change bed morphology and/or water quality but also affect the river ice regime. The length of the ice-affected season and the relative frequency of ice appearance might alter due to anthropogenic activities. Moreover, anthropogenically induced changes may vastly exceed climatic effects. When the prevailing non-natural impact co-varies with the trend of the expected climate trigger (e.g. winter air temperature), conclusions can be biased if the anthropogenic effects were not scrutinized in depth. This paper presents examples when changes in some characteristic feature of the river ice regime are related to human activities. These simple tests could be applied for other rivers, where similar anthropogenic impacts may be suspected to affect the river ice regime. © 2012 Elsevier Ltd and INQUA. Source

Laszlo P.,Eotvos Lorand University | Kern Z.,Institute for Geological and Geochemical Research | Kern Z.,University of Bern | Nagy B.,Eotvos Lorand University
Quaternary International | Year: 2013

Glacial landforms are commonly found throughout the highest belt (above ∼1700 m a.s.l.) of the Romanian Carpathians. This paper presents glacial geomorphological evidence from the Zânoaga Mare, Zânoaga Iezerului and the western part of Buhâescu valley complex situated on the northern slope of the Rodna Mountains, in the Eastern Carpathians, Romania. GIS-based geomorphological mapping reveals five sets of moraines in glacial phases assigned to the Late Pleistocene. The most extensive glacier was in western Buhâescu valley and had a surface area of 5 km2 and a length of 4.2 km and reached down to an altitude of 1086 m. Several methods were tested to determine the former ELAs of the glaciers. Using size-specific AAR, the average ELA for the oldest phase was 1765 m and rose to 1865, 1960, 2001 and 2025 m. The last and youngest phase was characterised only by cirque glaciers. Comparison with previous studies shows that extents were over-estimated. © 2012 Elsevier Ltd and INQUA. Source

Garamszegi B.,Eotvos Lorand University | Kern Z.,Institute for Geological and Geochemical Research
Dendrobiology | Year: 2014

Future of beech (Fagus sylvatica L.) in a changing climate is one of the greatest debates in Europe among the studies dealing with the climate change generated xeric limit shifting. We investigated a submontane beech stand’s growth response to climate change in Northern Hungary during the past 60 years following dendrochronological methods. Tree-ring width data were processed using three alternatives of standardization. To recover the basic climate-growth relationships for beech we analyzed the correlation between the tree-ring width indices and monthly precipitation and temperature data, furthermore two drought indices were employed. Late spring-early summer precipitation was the primary climatic factor governing the beech growth at the study site since the early 1950s, while summer heat played a secondary obstructive role documented by the significant negative correlation. A 30-years running window correlation was used to identify whether the climate-growth connections changed due to the unfavorable climatic trends. The results indicated no evidence of a distinct decline in radial increment, however, a significant increase in climatic impact on growth has been detected including probable changes and shifts in the vegetation period. © 2014 Polska Akademia Nauk. All rights reserved. Source

Kern Z.,University of Bern | Kern Z.,Oeschger Center for Climate Change Research | Kern Z.,Institute for Geological and Geochemical Research | Kohan B.,Eotvos Lorand University | And 2 more authors.
Atmospheric Chemistry and Physics | Year: 2014

Stable oxygen isotope composition of atmospheric precipitation (δ18Op) was scrutinized from 39 stations distributed over Switzerland and its border zone. Monthly amount-weighted δ18Op values averaged over the 1995-2000 period showed the expected strong linear altitude dependence (-0.15 to-0.22‰ per 100 m) only during the summer season (May-September). Steeper gradients (∼-0.56 to-0.60‰ per 100 m) were observed for winter months over a low elevation belt, while hardly any altitudinal difference was seen for high elevation stations. This dichotomous pattern could be explained by the characteristically shallower vertical atmospheric mixing height during winter season and provides empirical evidence for recently simulated effects of stratified atmospheric flow on orographic precipitation isotopic ratios. This helps explain "anomalous" deflected altitudinal water isotope profiles reported from many other high relief regions. Grids and isotope distribution maps of the monthly δ18Op have been calculated over the study region for 1995-1996. The adopted interpolation method took into account both the variable mixing heights and the seasonal difference in the isotopic lapse rate and combined them with residual kriging. The presented data set allows a point estimation of δ18Op with monthly resolution. According to the test calculations executed on subsets, this biannual data set can be extended back to 1992 with maintained fidelity and, with a reduced station subset, even back to 1983 at the expense of faded reliability of the derived δ18Op estimates, mainly in the eastern part of Switzerland. Before 1983, reliable results can only be expected for the Swiss Plateau since important stations representing eastern and south-western Switzerland were not yet in operation. © Author(s) 2014. CC Attribution 3.0 License. Source

Discover hidden collaborations