Other affiliations: Oeschger Centre for Climate Change Research
Bio: Daniel Nievergelt is an academic researcher from Swiss Federal Institute for Forest, Snow and Landscape Research. The author has contributed to research in topics: Dendrochronology & Radiocarbon dating. The author has an hindex of 18, co-authored 44 publications receiving 1670 citations. Previous affiliations of Daniel Nievergelt include Oeschger Centre for Climate Change Research.
TL;DR: In this article, a reconstruction of the European Alps for the a.d. 755-2004 period is presented, based on 180 recent and historic larch [Larix decidua mill] density series.
Abstract: Annually resolved summer temperatures for the European Alps are described. The reconstruction covers the a.d. 755–2004 period and is based on 180 recent and historic larch [Larix decidua Mill.] density series. The regional curve standardization method was applied to preserve interannual to multicentennial variations in this high-elevation proxy dataset. Instrumental measurements from high- (low-) elevation grid boxes back to 1818 (1760) reveal strongest growth response to current-year June–September mean temperatures. The reconstruction correlates at 0.7 with high-elevation temperatures back to 1818, with a greater signal in the higher-frequency domain (r = 0.8). Low-elevation instrumental data back to 1760 agree with the reconstruction’s interannual variation, although a decoupling between (warmer) instrumental and (cooler) proxy data before ∼1840 is noted. This offset is larger than during any period of overlap with more recent high-elevation instrumental data, even though the proxy time series...
TL;DR: In this paper, an analysis of maximum latewood density data from northern Scandinavia, along with published dendrochronological records, finds evidence that previous tree-ring-reliant reconstructions of large-scale near-surface air temperature underestimated long-term pre-industrial warmth during Medieval and Roman times.
Abstract: Based on an analysis of maximum latewood density data from northern Scandinavia, along with published dendrochronological records, this study finds evidence that previous tree-ring-reliant reconstructions of large-scale near-surface air temperature underestimated long-term pre-industrial warmth during Medieval and Roman times. Solar insolation changes, resulting from long-term oscillations of orbital configurations1, are an important driver of Holocene climate2,3. The forcing is substantial over the past 2,000 years, up to four times as large as the 1.6 W m−2 net anthropogenic forcing since 1750 (ref. 4), but the trend varies considerably over time, space and with season5. Using numerous high-latitude proxy records, slow orbital changes have recently been shown6 to gradually force boreal summer temperature cooling over the common era. Here, we present new evidence based on maximum latewood density data from northern Scandinavia, indicating that this cooling trend was stronger (−0.31 °C per 1,000 years, ±0.03 °C) than previously reported, and demonstrate that this signature is missing in published tree-ring proxy records. The long-term trend now revealed in maximum latewood density data is in line with coupled general circulation models7,8 indicating albedo-driven feedback mechanisms and substantial summer cooling over the past two millennia in northern boreal and Arctic latitudes. These findings, together with the missing orbital signature in published dendrochronological records, suggest that large-scale near-surface air-temperature reconstructions9,10,11,12,13 relying on tree-ring data may underestimate pre-instrumental temperatures including warmth during Medieval and Roman times.
TL;DR: A microtome designed for the surface preparation of entire increment cores allows cutting plane surfaces on cores up to a length of 40 cm as discussed by the authors, which can be used for a more detailed analysis of variations in the tracheid structure of conifers and vessel sizes of oak.
Abstract: A microtome designed for the surface preparation of entire increment cores allows cutting plane surfaces on cores up to a length of 40 cm. Compared to the common sanding procedure, the wood cells of the annual rings remain open, not filled with swarf, and the cell walls are smooth and hence clearly visible. This article aims at describing the functionality of the microtome and the procedures needed for an accurate surface preparation to achieve a good contrast for subsequent image analysis. Possible applications for a more detailed analysis of variations in the tracheid structure of conifers and vessel sizes of oak are presented, which can be included in time series analyses.
TL;DR: The long-term history of Zeiraphera diniana Gn.
Abstract: The long-term history of Zeiraphera diniana Gn. (the larch budmoth, LBM) outbreaks was reconstructed from tree rings of host subalpine larch in the European Alps. This record was derived from 47513...
TL;DR: In this article, the authors quantify the response of radial conifer stem size to environmental fluctuations via a novel assessment of tree circadian cycles, and show that changes in precipitation, temperature and cloud cover have a substantial effect on typical growing season diurnal cycles; amplitudes were nine times smaller on rainy days (>10mm), and daily amplitudes are approximately 40% larger when the mean daily temperature is 15-20°C than when it is 5-10°C.
Abstract: Climate affects the timing, rate and dynamics of tree growth, over time scales ranging from seconds to centuries. Monitoring how a tree's stem radius varies over these time scales can provide insight into intra-annual stem dynamics and improve our understanding of climate impacts on tree physiology and growth processes. Here, we quantify the response of radial conifer stem size to environmental fluctuations via a novel assessment of tree circadian cycles. We analyze four years of sub-hourly data collected from 56 larch and spruce trees growing along a natural temperature gradient of ∼6 °C in the central Swiss Alps. During the growing season, tree stem diameters were greatest at mid-morning and smallest in the late evening, reflecting the daily cycle of water uptake and loss. Along the gradient, amplitudes calculated from the stem radius cycle were ∼50% smaller at the upper site (∼2200 m a.s.l.) relative to the lower site (∼800 m a.s.l.). We show changes in precipitation, temperature and cloud cover have a substantial effect on typical growing season diurnal cycles; amplitudes were nine times smaller on rainy days (>10 mm), and daily amplitudes are approximately 40% larger when the mean daily temperature is 15–20 °C than when it is 5–10 °C. We find that over the growing season in the sub-alpine forests, spruce show greater daily stem water movement than larch. However, under projected future warming, larch could experience up to 50% greater stem water use, which may severely affect future growth on already dry sites. Our data further indicate that because of the confounding influences of radial growth and short-term water dynamics on stem size, conventional methodology probably overstates the effect of water-linked meteorological variables (i.e. precipitation and relative humidity) on intra-annual tree growth. We suggest future studies use intra-seasonal measurements of cell development and consider whether climatic factors produce reversible changes in stem diameter. These study design elements may help researchers more accurately quantify and attribute changes in forest productivity in response to future warming.
Queen's University Belfast1, University of St Andrews2, Aix-Marseille University3, Historic England4, University of Sheffield5, University of Oxford6, Alfred Wegener Institute for Polar and Marine Research7, University of Minnesota8, Xi'an Jiaotong University9, Nanjing Normal University10, University of Hohenheim11, University of Kiel12, Lawrence Livermore National Laboratory13, University of California, Santa Cruz14, ETH Zurich15, University of Waikato16, Woods Hole Oceanographic Institution17, Heidelberg University18, Cornell University19, Lund University20, University of New South Wales21, University of Arizona22, University of Groningen23, University of Bristol24, University of Glasgow25, University of California, Irvine26, University of Bern27, Aarhus University28, Nagoya University29, Swiss Federal Institute for Forest, Snow and Landscape Research30, National Museum of Japanese History31, University of Bologna32
TL;DR: In this article, the international 14C calibration curves for both the Northern and Southern Hemispheres, as well as for the ocean surface layer, have been updated to include a wealth of new data and extended to 55,000 cal BP.
Abstract: Radiocarbon (14C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric 14C concentration. Although calibration curves are constructed from independently dated archives, they invariably require revision as new data become available and our understanding of the Earth system improves. In this volume the international 14C calibration curves for both the Northern and Southern Hemispheres, as well as for the ocean surface layer, have been updated to include a wealth of new data and extended to 55,000 cal BP. Based on tree rings, IntCal20 now extends as a fully atmospheric record to ca. 13,900 cal BP. For the older part of the timescale, IntCal20 comprises statistically integrated evidence from floating tree-ring chronologies, lacustrine and marine sediments, speleothems, and corals. We utilized improved evaluation of the timescales and location variable 14C offsets from the atmosphere (reservoir age, dead carbon fraction) for each dataset. New statistical methods have refined the structure of the calibration curves while maintaining a robust treatment of uncertainties in the 14C ages, the calendar ages and other corrections. The inclusion of modeled marine reservoir ages derived from a three-dimensional ocean circulation model has allowed us to apply more appropriate reservoir corrections to the marine 14C data rather than the previous use of constant regional offsets from the atmosphere. Here we provide an overview of the new and revised datasets and the associated methods used for the construction of the IntCal20 curve and explore potential regional offsets for tree-ring data. We discuss the main differences with respect to the previous calibration curve, IntCal13, and some of the implications for archaeology and geosciences ranging from the recent past to the time of the extinction of the Neanderthals.
01 Dec 2013
TL;DR: This paper found that the most intensive glacier shrinkage is in the Himalayan region, whereas glacial retreat in the Pamir Plateau region is less apparent, due to changes in atmospheric circulations and precipitation patterns.
Abstract: Glacial melting in the Tibetan Plateau affects the water resources of millions of people. This study finds that—partly owing to changes in atmospheric circulations and precipitation patterns—the most intensive glacier shrinkage is in the Himalayan region, whereas glacial retreat in the Pamir Plateau region is less apparent.
TL;DR: Recon reconstructions of the past 1500 years suggest that recent warming is unprecedented in that time, and regional and global temperature anomalies for the past 11,300 years from 73 globally distributed records are provided.
Abstract: Surface temperature reconstructions of the past 1500 years suggest that recent warming is unprecedented in that time. Here we provide a broader perspective by reconstructing regional and global temperature anomalies for the past 11,300 years from 73 globally distributed records. Early Holocene (10,000 to 5000 years ago) warmth is followed by ~0.7°C cooling through the middle to late Holocene (<5000 years ago), culminating in the coolest temperatures of the Holocene during the Little Ice Age, about 200 years ago. This cooling is largely associated with ~2°C change in the North Atlantic. Current global temperatures of the past decade have not yet exceeded peak interglacial values but are warmer than during ~75% of the Holocene temperature history. Intergovernmental Panel on Climate Change model projections for 2100 exceed the full distribution of Holocene temperature under all plausible greenhouse gas emission scenarios.
Oeschger Centre for Climate Change Research1, Swiss Federal Institute for Forest, Snow and Landscape Research2, University of Freiburg3, University of Innsbruck4, Harvard University5, University of Arizona6, École Polytechnique Fédérale de Lausanne7, United States Department of State8, Deutsches Archäologisches Institut9, University of Giessen10, University of Mainz11
TL;DR: Reconstruction of tree ring–based reconstructions of central European summer precipitation and temperature variability over the past 2500 years may provide a basis for counteracting the recent political and fiscal reluctance to mitigate projected climate change.
Abstract: Climate variations influenced the agricultural productivity, health risk, and conflict level of preindustrial societies. Discrimination between environmental and anthropogenic impacts on past civilizations, however, remains difficult because of the paucity of high-resolution paleoclimatic evidence. We present tree ring-based reconstructions of central European summer precipitation and temperature variability over the past 2500 years. Recent warming is unprecedented, but modern hydroclimatic variations may have at times been exceeded in magnitude and duration. Wet and warm summers occurred during periods of Roman and medieval prosperity. Increased climate variability from ~250 to 600 C.E. coincided with the demise of the western Roman Empire and the turmoil of the Migration Period. Such historical data may provide a basis for counteracting the recent political and fiscal reluctance to mitigate projected climate change.
Federal Urdu University1, Columbia University2, Woods Hole Oceanographic Institution3, Addis Ababa University4, Indian Institute of Tropical Meteorology5, University of Trieste6, Swiss Federal Institute for Forest, Snow and Landscape Research7, University of Bergen8, University of Montpellier9, Austral University of Chile10, University of Chile11, University of Tasmania12, Australian Antarctic Division13, National Oceanic and Atmospheric Administration14, University of Mainz15, Xishuangbanna Tropical Botanical Garden16, Nepal Academy of Science and Technology17, Chinese Academy of Sciences18, University of Melbourne19, Complutense University of Madrid20, Université catholique de Louvain21, University of the Witwatersrand22, Hydrologic Research Center23, University of Bern24, University of Helsinki25, Northern Arizona University26, Fukushima University27, Stockholm University28, Université Paris-Saclay29, National Institute of Water and Atmospheric Research30, University of Giessen31, Swansea University32, Desert Research Institute33, National Scientific and Technical Research Council34, British Antarctic Survey35, Nagoya University36, University of Brighton37, Florida State University38, Alfred Wegener Institute for Polar and Marine Research39, University of Exeter40, University of New South Wales41, Centro de Estudios Científicos42, University of Florence43, University of Texas at Austin44, Russian Academy of Sciences45, University of Washington46, National Centre for Antarctic and Ocean Research47, University of Arizona48, Ghent University49, University of Ottawa50, University of Copenhagen51, University of Colorado Boulder52, Shinshu University53
TL;DR: The authors reconstructed past temperatures for seven continental-scale regions during the past one to two millennia and found that the most coherent feature in nearly all of the regional temperature reconstructions is a long-term cooling trend, which ended late in the nineteenth century.
Abstract: Past global climate changes had strong regional expression To elucidate their spatio-temporal pattern, we reconstructed past temperatures for seven continental-scale regions during the past one to two millennia The most coherent feature in nearly all of the regional temperature reconstructions is a long-term cooling trend, which ended late in the nineteenth century At multi-decadal to centennial scales, temperature variability shows distinctly different regional patterns, with more similarity within each hemisphere than between them There were no globally synchronous multi-decadal warm or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age, but all reconstructions show generally cold conditions between ad 1580 and 1880, punctuated in some regions by warm decades during the eighteenth century The transition to these colder conditions occurred earlier in the Arctic, Europe and Asia than in North America or the Southern Hemisphere regions Recent warming reversed the long-term cooling; during the period ad 1971–2000, the area-weighted average reconstructed temperature was higher than any other time in nearly 1,400 years