Showing papers by "Hubertus Fischer published in 2018"
01 Jan 2018
TL;DR: In this article, the authors present a survey of women's sportswriters in South Africa and Ivory Coast, including: Marco Bindi (Italy), Sally Brown (UK), Ines Camilloni (Argentina), Arona Diedhiou (Ivory Coast/Senegal), Riyanti Djalante (Japan/Indonesia), Kristie L. Ebi (USA), Francois Engelbrecht (South Africa), Joel Guiot (France), Yasuaki Hijioka (Japan), Shagun Mehrotra (USA/India), Ant
Abstract: Lead Authors: Marco Bindi (Italy), Sally Brown (UK), Ines Camilloni (Argentina), Arona Diedhiou (Ivory Coast/Senegal), Riyanti Djalante (Japan/Indonesia), Kristie L. Ebi (USA), Francois Engelbrecht (South Africa), Joel Guiot (France), Yasuaki Hijioka (Japan), Shagun Mehrotra (USA/India), Antony Payne (UK), Sonia I. Seneviratne (Switzerland), Adelle Thomas (Bahamas), Rachel Warren (UK), Guangsheng Zhou (China)
614 citations
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Université Paris-Saclay1, University of Reading2, University of Leeds3, Max Planck Society4, University of Tokyo5, Japan Agency for Marine-Earth Science and Technology6, University of Cologne7, University of Oregon8, University College London9, Université catholique de Louvain10, Complutense University of Madrid11, University of Bern12, University of Bristol13, University of Birmingham14, University of Chile15, Cornell University16, University of Toronto17, University of Tasmania18, VU University Amsterdam19, Goddard Institute for Space Studies20, St. John's University21, Chinese Academy of Sciences22
TL;DR: In this paper, a series of GMD papers on the PMIP4-CMIP6 experiments are presented, with a focus on their novel features compared to the experiments performed in previous phases of PMIP and CMIP.
Abstract: . This paper is the first of a series of four GMD papers on the PMIP4-CMIP6 experiments. Part 2 (Otto-Bliesner et al., 2017) gives details about the two PMIP4-CMIP6 interglacial experiments, Part 3 (Jungclaus et al., 2017) about the last millennium experiment, and Part 4 (Kageyama et al., 2017) about the Last Glacial Maximum experiment. The mid-Pliocene Warm Period experiment is part of the Pliocene Model Intercomparison Project (PlioMIP) – Phase 2, detailed in Haywood et al. (2016). The goal of the Paleoclimate Modelling Intercomparison Project (PMIP) is to understand the response of the climate system to different climate forcings for documented climatic states very different from the present and historical climates. Through comparison with observations of the environmental impact of these climate changes, or with climate reconstructions based on physical, chemical, or biological records, PMIP also addresses the issue of how well state-of-the-art numerical models simulate climate change. Climate models are usually developed using the present and historical climates as references, but climate projections show that future climates will lie well outside these conditions. Palaeoclimates very different from these reference states therefore provide stringent tests for state-of-the-art models and a way to assess whether their sensitivity to forcings is compatible with palaeoclimatic evidence. Simulations of five different periods have been designed to address the objectives of the sixth phase of the Coupled Model Intercomparison Project (CMIP6): the millennium prior to the industrial epoch (CMIP6 name: past1000); the mid-Holocene, 6000 years ago (midHolocene); the Last Glacial Maximum, 21 000 years ago (lgm); the Last Interglacial, 127 000 years ago (lig127k); and the mid-Pliocene Warm Period, 3.2 million years ago (midPliocene-eoi400). These climatic periods are well documented by palaeoclimatic and palaeoenvironmental records, with climate and environmental changes relevant for the study and projection of future climate changes. This paper describes the motivation for the choice of these periods and the design of the numerical experiments and database requests, with a focus on their novel features compared to the experiments performed in previous phases of PMIP and CMIP. It also outlines the analysis plan that takes advantage of the comparisons of the results across periods and across CMIP6 in collaboration with other MIPs.
189 citations
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Oeschger Centre for Climate Change Research1, University of Bern2, University of New South Wales3, Oregon State University4, Australian National University5, University of Cambridge6, Max Planck Society7, British Antarctic Survey8, University of Copenhagen9, University of Bordeaux10, Lamont–Doherty Earth Observatory11, University of Bremen12, University of Toronto13, Durham University14, Leibniz Center for Tropical Marine Ecology15, Alfred Wegener Institute for Polar and Marine Research16, University of Geneva17, Ca' Foscari University of Venice18, Siberian Federal University19, GNS Science20, Queen's University21, University of Lausanne22, Université du Québec à Montréal23, University of Southern California24, University of Nebraska–Lincoln25, University of Bristol26, Adam Mickiewicz University in Poznań27, Yale University28, Université Paris-Saclay29, National Center for Atmospheric Research30, Bjerknes Centre for Climate Research31, École pratique des hautes études32, United States Global Change Research Program33, University of Kiel34, Lund University35, Chinese Academy of Sciences36, Lehigh University37, Northeast Normal University38, Utrecht University39, ETH Zurich40, Peking University41
TL;DR: In this article, an observation-based synthesis of the understanding of past intervals with temperatures within the range of projected future warming suggests that there is a low risk of runaway greenhouse gas feedbacks for global warming of no more than 2 °C.
Abstract: Over the past 3.5 million years, there have been several intervals when climate conditions were warmer than during the pre-industrial Holocene. Although past intervals of warming were forced differently than future anthropogenic change, such periods can provide insights into potential future climate impacts and ecosystem feedbacks, especially over centennial-to-millennial timescales that are often not covered by climate model simulations. Our observation-based synthesis of the understanding of past intervals with temperatures within the range of projected future warming suggests that there is a low risk of runaway greenhouse gas feedbacks for global warming of no more than 2 °C. However, substantial regional environmental impacts can occur. A global average warming of 1–2 °C with strong polar amplification has, in the past, been accompanied by significant shifts in climate zones and the spatial distribution of land and ocean ecosystems. Sustained warming at this level has also led to substantial reductions of the Greenland and Antarctic ice sheets, with sea-level increases of at least several metres on millennial timescales. Comparison of palaeo observations with climate model results suggests that, due to the lack of certain feedback processes, model-based climate projections may underestimate long-term warming in response to future radiative forcing by as much as a factor of two, and thus may also underestimate centennial-to-millennial-scale sea-level rise.
160 citations
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Oeschger Centre for Climate Change Research1, British Antarctic Survey2, Australian National University3, University of Copenhagen4, Alfred Wegener Institute for Polar and Marine Research5, National Institute of Polar Research6, Colorado State University7, Geological Survey of Canada8, University of Ottawa9, Chinese Academy of Sciences10, University of Grenoble11, Ca' Foscari University of Venice12, Inha University13, Stockholm University14, Lund University15, Nevada System of Higher Education16, University of Cambridge17
TL;DR: High-resolution aerosol records from the Greenland NEEM ice core are used to reconstruct the environmental alterations in aerosol source regions accompanying changes in climate, finding strongly reduced terrestrial biogenic emissions during glacial times reflecting net loss of vegetated area in North America.
Abstract: The Northern Hemisphere experienced dramatic changes during the last glacial, featuring vast ice sheets and abrupt climate events, while high northern latitudes during the last interglacial (Eemian) were warmer than today. Here we use high-resolution aerosol records from the Greenland NEEM ice core to reconstruct the environmental alterations in aerosol source regions accompanying these changes. Separating source and transport effects, we find strongly reduced terrestrial biogenic emissions during glacial times reflecting net loss of vegetated area in North America. Rapid climate changes during the glacial have little effect on terrestrial biogenic aerosol emissions. A strong increase in terrestrial dust emissions during the coldest intervals indicates higher aridity and dust storm activity in East Asian deserts. Glacial sea salt aerosol emissions in the North Atlantic region increase only moderately (50%), likely due to sea ice expansion. Lower aerosol concentrations in Eemian ice compared to the Holocene are mainly due to shortened atmospheric residence time, while emissions changed little.
85 citations
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TL;DR: In this paper, the authors use cosmogenic radionuclides (10Be, 36Cl, 14C ) to link Greenland ice-core records to U∕Th -dated speleothems, quantify offsets between the two timescales, and improve their absolute dating back to 45'000 years ago.
Abstract: . During the last glacial period Northern Hemisphere climate was characterized
by extreme and abrupt climate changes, so-called Dansgaard–Oeschger (DO)
events. Most clearly observed as temperature changes in Greenland ice-core
records, their climatic imprint was geographically widespread. However, the
temporal relation between DO events in Greenland and other regions is
uncertain due to the chronological uncertainties of each archive, limiting
our ability to test hypotheses of synchronous change. In contrast, the
assumption of direct synchrony of climate changes forms the basis of many
timescales. Here, we use cosmogenic radionuclides ( 10Be ,
36Cl , 14C ) to link Greenland ice-core records to
U∕Th -dated speleothems, quantify offsets between the two timescales, and
improve their absolute dating back to 45 000 years ago. This approach allows
us to test the assumption that DO events occurred synchronously between
Greenland ice-core and tropical speleothem records with unprecedented
precision. We find that the onset of DO events occurs within synchronization
uncertainties in all investigated records. Importantly, we demonstrate that
local discrepancies remain in the temporal development of rapid climate
change for specific events and speleothems. These may either be related to
the location of proxy records relative to the shifting atmospheric fronts or
to underestimated U∕Th dating uncertainties. Our study thus highlights
the potential for misleading interpretations of the Earth system when
applying the common practice of climate wiggle matching.
62 citations
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National Institute for Environmental Studies1, Max Planck Society2, Utrecht University3, University of California, Irvine4, Norco College5, Tohoku University6, National Institute of Polar Research7, Pennsylvania State University8, University of Bern9, Institute of Arctic and Alpine Research10, National Institute of Water and Atmospheric Research11, University of Copenhagen12, Royal Holloway, University of London13, Portland State University14, Heidelberg University15
TL;DR: In this paper, the authors report results from a worldwide interlaboratory comparison of samples among laboratories that measure (or measured) stable carbon and hydrogen isotope ratios of atmospheric CH4 (δ13C-CH4 and δD-Ch4).
Abstract: . We report results from a worldwide interlaboratory comparison of samples among laboratories that measure (or measured) stable carbon and hydrogen isotope ratios of atmospheric CH4 (δ13C-CH4 and δD-CH4). The offsets among the laboratories are larger than the measurement reproducibility of individual laboratories. To disentangle plausible measurement offsets, we evaluated and critically assessed a large number of intercomparison results, some of which have been documented previously in the literature. The results indicate significant offsets of δ13C-CH4 and δD-CH4 measurements among data sets reported from different laboratories; the differences among laboratories at modern atmospheric CH4 level spread over ranges of 0.5 ‰ for δ13C-CH4 and 13 ‰ for δD-CH4. The intercomparison results summarized in this study may be of help in future attempts to harmonize δ13C-CH4 and δD-CH4 data sets from different laboratories in order to jointly incorporate them into modelling studies. However, establishing a merged data set, which includes δ13C-CH4 and δD-CH4 data from multiple laboratories with desirable compatibility, is still challenging due to differences among laboratories in instrument settings, correction methods, traceability to reference materials and long-term data management. Further efforts are needed to identify causes of the interlaboratory measurement offsets and to decrease those to move towards the best use of available δ13C-CH4 and δD-CH4 data sets.
28 citations
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TL;DR: In this article, the authors present new methane concentration and stable hydrogen and carbon isotope data measured on ice core samples from both Greenland and Antarctica over the first half of the Holocene.
Abstract: . Atmospheric methane concentration shows a well-known decrease over the first
half of the Holocene following the Northern Hemisphere summer insolation
before it started to increase again to preindustrial values. There is a
debate about what caused this change in the methane concentration evolution, in
particular, whether an early anthropogenic influence or natural emissions led
to the reversal of the atmospheric CH4 concentration evolution. Here, we
present new methane concentration and stable hydrogen and carbon isotope data
measured on ice core samples from both Greenland and Antarctica over the
Holocene. With the help of a two-box model and the full suite of CH4
parameters, the new data allow us to quantify the total methane emissions in
the Northern Hemisphere and Southern Hemisphere separately as well as their stable isotopic
signatures, while interpretation of isotopic records of only one hemisphere
may lead to erroneous conclusions. For the first half of the Holocene our
results indicate an asynchronous decrease in Northern Hemisphere and Southern Hemisphere
CH4 emissions by more than
30 Tg CH4 yr −1 in total,
accompanied by a drop in the northern carbon isotopic source signature of
about −3 ‰. This cannot be explained by a change in
the source mix alone but requires shifts in the isotopic signature of the
sources themselves caused by changes in the precursor material for the
methane production. In the second half of the Holocene, global CH4
emissions increased by about 30 Tg CH4 yr −1 , while
preindustrial isotopic emission signatures remained more or less constant.
However, our results show that this early increase in methane emissions took
place in the Southern Hemisphere, while Northern Hemisphere emissions started
to increase only about 2000 years ago. Accordingly, natural emissions in the
southern tropics appear to be the main cause of the CH4 increase
starting 5000 years before present, not supporting an early anthropogenic influence on the
global methane budget by East Asian land use changes.
25 citations
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TL;DR: The first high-resolution Pb and Sr isotopic evidence for a significant Saharan dust influence in Greenland during the last glacial period, back to ~31 kyr ago, is reported, finding that during Greenland Stadials 3–5.1, the primary dust provenance was East Asia, as previously proposed.
Abstract: Dust concentrations in Greenland ice show pronounced glacial/interglacial variations with almost two orders of magnitude increase during the Last Glacial Maximum. Greenland glacial dust was previously sourced to two East Asian deserts: the Taklimakan and Gobi deserts. Here we report the first high-resolution Pb and Sr isotopic evidence for a significant Saharan dust influence in Greenland during the last glacial period, back to ~31 kyr ago, from the Greenland NEEM ice core. We find that during Greenland Stadials 3–5.1 (~31 to 23 kyr ago), the primary dust provenance was East Asia, as previously proposed. Subsequently, the Saharan isotopic signals emerge during Greenland Stadials 2.1a–2.1c (~22.6 to 14.7 kyr ago) and from the late Bolling-Allerod to the Younger Dryas periods (~13.6 to 12 kyr ago), coincident with increased aridity in the Sahara and efficient northward transport of dust during these cold periods. A mixing isotopic model proposes the Sahara as an important source, accounting for contribution to Greenland glacial dust of up to 50%, particularly during Greenland Stadial 2.1b and the late Bolling-Allerod to the Younger Dryas periods. Our findings provide new insights into climate-related dust provenance changes and essential paleoclimatic constraints on dust-climate feedbacks in northern high latitudes.
22 citations
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Oeschger Centre for Climate Change Research1, University of Bern2, University of New South Wales3, Oregon State University4, Australian National University5, University of Cambridge6, Max Planck Society7, British Antarctic Survey8, University of Copenhagen9, University of Bordeaux10, Lamont–Doherty Earth Observatory11, University of Bremen12, University of Toronto13, Durham University14, Leibniz Center for Tropical Marine Ecology15, Alfred Wegener Institute for Polar and Marine Research16, University of Geneva17, Ca' Foscari University of Venice18, Siberian Federal University19, GNS Science20, Queen's University21, University of Lausanne22, Université du Québec à Montréal23, University of Southern California24, University of Nebraska–Lincoln25, University of Bristol26, Adam Mickiewicz University in Poznań27, Yale University28, Université Paris-Saclay29, National Center for Atmospheric Research30, Bjerknes Centre for Climate Research31, École pratique des hautes études32, United States Global Change Research Program33, University of Kiel34, Lund University35, Chinese Academy of Sciences36, Lehigh University37, Northeast Normal University38, Utrecht University39, ETH Zurich40, Peking University41
TL;DR: The complexity of residual ice cover makes it likely that HTM warming was regional, rather than global, and its peak warmth thus had different timing in different locations as discussed by the authors, and this complexity makes it possible to identify the most likely location of HTM warmings.
Abstract: In the version of this Review Article originally published, ref. 10 was mistakenly cited instead of ref. 107 at the end of the sentence: “This complexity of residual ice cover makes it likely that HTM warming was regional, rather than global, and its peak warmth thus had different timing in different locations.” In addition, for ref. 108, Scientific Reports was incorrectly given as the publication name; it should have been Scientific Data. These errors have now been corrected in the online versions.
9 citations
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TL;DR: In this article, the authors used high-resolution multi-proxy records of sea-salt (derived from sea spray and sea ice over the North Atlantic) and terrestrial aerosol concentrations over the period 10-60'ka from the Greenland NGRIP and NEEM ice cores in conjunction with local precipitation and temperature proxies from one of the cores to investigate the progression of environmental changes at the onset of the DO warming events at annual to multi-annual resolution.
Abstract: . During the last glacial period, proxy records throughout the Northern Hemisphere document a succession of rapid millennial-scale warming events, called Dansgaard-Oeschger (DO) events. A range of different mechanisms have been proposed that can produce similar warming in model experiments, however the progression and ultimate trigger of the events is still unknown. Because of their fast nature, the progression is challenging to reconstruct from paleoclimate data due to the limited temporal resolution achievable in many archives and cross-dating uncertainties between records. Here we use new high-resolution multi-proxy records of sea-salt (derived from sea spray and sea ice over the North Atlantic) and terrestrial (derived from the Central Asian deserts) aerosol concentrations over the period 10–60 ka from the Greenland NGRIP and NEEM ice cores in conjunction with local precipitation and temperature proxies from one of the cores to investigate the progression of environmental changes at the onset of the warming events at annual to multi-annual resolution. Our results show on average a small lead of the changes in both local precipitation and terrestrial dust aerosol concentrations over the change in sea-salt aerosol concentrations and local temperature of approximately one decade. This suggests that, connected to the reinvigoration of the Atlantic Meridional Overturning Circulation and the warming in the North Atlantic, both synoptic and hemispheric atmospheric circulation change at the onset of the DO warming, affecting both the moisture transport to Greenland and the Asian monsoon systems. Taken at face value, this suggests that a collapse of the sea-ice cover was not the initial trigger for the DO events.
3 citations
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TL;DR: The complexity of residual ice cover makes it likely that HTM warming was regional, rather than global, and its peak warmth thus had different timing in different locations as discussed by the authors, and this complexity makes it possible to identify the most likely location of HTM warmings.
Abstract: In the version of this Review Article originally published, ref. 10 was mistakenly cited instead of ref. 107 at the end of the sentence: “This complexity of residual ice cover makes it likely that HTM warming was regional, rather than global, and its peak warmth thus had different timing in different locations.” In addition, for ref. 108, Scientific Reports was incorrectly given as the publication name; it should have been Scientific Data. These errors have now been corrected in the online versions.