CO 2 over the past 5 million years: Continuous simulation and new δ 11 B-based proxy data

Oak and pine samples housed at the Institute of Botany, University of Hohenheim, are the backbone of the early Holocene part of the radiocarbon calibration curve, published in 1993 (Becker 1993; Kromer and Becker 1993; Stuiver and Becker 1993; Vogel et al. 1993). Since then the chronologies have been revised. The revisions include 1) the discovery of 41 missing years in the oak chronology and 2) a shift of 54 yr for the oldest part back into the past. The oak chronology was also extended with new samples as far back as 10,429 BP (8480 BC). In addition, the formerly tentatively dated pine chronology (Becker 1993) has been rebuilt and shifted to an earlier date. It is now positioned by 14C matching at 11,871-9900 BP (9922–7951 BC) with an uncertainty of ±20 yr (Kromer and Spurk 1998). With these new chronologies the 14C calibration curve can now be corrected, eliminating the discrepancy in the dating of the Younger Dryas/Preboreal transition between the proxy data of the GRIP and GISP ice cores (Johnsen et al. 1992; Taylor et al. 1993), the varve chronology of Lake Gościąż (Goslar et al. 1995) and the pine chronology (Becker, Kromer and Trimborn 1991).

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Characteristics of cold–warm variation in the Hetao region and its surrounding areas in China during the past 5000 years

Climate of the Past ◽

10.5194/cp-6-475-2010 ◽

2010 ◽

Vol 6 (4) ◽

pp. 475-481 ◽

Cited By ~ 1

Author(s):

M.-Q. Li ◽

Q.-S. Ge ◽

Z.-X. Hao ◽

J.-Y. Zheng ◽

S.-F. He

Keyword(s):

Climate Changes ◽

Mean Value ◽

Data Series ◽

Proxy Data ◽

Average Temperature ◽

The Past ◽

The Mean ◽

Temperature Proxy ◽

Surrounding Areas

Abstract. Using six long-term temperature proxy data series derived from different natural evidences, including pollens and lake-sediments, we reconstructed a temperature series with a 100-yr time resolution for the past 5000 yr in the Hetao region and its surrounding areas. The resulting series suggests that, on a millennial timescale, temperatures in the region were higher than the mean value of the whole series during the 5000~2600 years before present (yr BP) period, and became relatively low comparing with the average temperature of the whole series after 2600 yr BP. Within these two periods, temperature fluctuations comprising numerous short, multi-centennial intervals also existed. A comparison between our reconstructed series and other series in China and across the Northern Hemisphere indicate that, on a long-term scale, cold–warm variations had been in phase across the whole hemisphere during the past 5000 years; on the century to multi-century scale, the beginning and the ending times varied from region to region, thus implying that climate changes did not occur simultaneously in different regions.

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Reconstructing the evolution of ice sheets, sea level, and atmospheric CO<sub>2</sub> during the past 3.6 million years

Climate of the Past ◽

10.5194/cp-17-361-2021 ◽

2021 ◽

Vol 17 (1) ◽

pp. 361-377

Author(s):

Constantijn J. Berends ◽

Bas de Boer ◽

Roderik S. W. van de Wal

Keyword(s):

Sea Level ◽

Radiative Forcing ◽

Climate Model ◽

Ice Sheets ◽

Early Pleistocene ◽

Glacial Cycles ◽

Proxy Data ◽

Late Pliocene ◽

Ice Volume ◽

The Past

Abstract. Understanding the evolution of, and the interactions between, ice sheets and the global climate over geological timescales is important for being able to project their future evolution. However, direct observational evidence of past CO2 concentrations, and the implied radiative forcing, only exists for the past 800 000 years. Records of benthic δ18O date back millions of years but contain signals from both land ice volume and ocean temperature. In recent years, inverse forward modelling has been developed as a method to disentangle these two signals, resulting in mutually consistent reconstructions of ice volume, temperature, and CO2. We use this approach to force a hybrid ice-sheet–climate model with a benthic δ18O stack, reconstructing the evolution of the ice sheets, global mean sea level, and atmospheric CO2 during the late Pliocene and the Pleistocene, from 3.6 million years (Myr) ago to the present day. During the warmer-than-present climates of the late Pliocene, reconstructed CO2 varies widely, from 320–440 ppmv for warm periods to 235–250 ppmv for the early glacial excursion ∼3.3 million years ago. Sea level is relatively stable during this period, with maxima of 6–14 m and minima of 12–26 m during glacial episodes. Both CO2 and sea level are within the wide ranges of values covered by available proxy data for this period. Our results for the Pleistocene agree well with the ice-core CO2 record, as well as with different available sea-level proxy data. For the Early Pleistocene, 2.6–1.2 Myr ago, we simulate 40 kyr glacial cycles, with interglacial CO2 decreasing from 280–300 ppmv at the beginning of the Pleistocene to 250–280 ppmv just before the Mid-Pleistocene Transition (MPT). Peak glacial CO2 decreases from 220–250 to 205–225 ppmv during this period. After the MPT, when the glacial cycles change from 40 to 80 120 kyr cyclicity, the glacial–interglacial contrast increases, with interglacial CO2 varying between 250–320 ppmv and peak glacial values decreasing to 170–210 ppmv.

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Variability of summer precipitation over Eastern China during the last millennium

Climate of the Past ◽

10.5194/cp-5-129-2009 ◽

2009 ◽

Vol 5 (2) ◽

pp. 129-141 ◽

Cited By ~ 25

Author(s):

C. Shen ◽

W.-C. Wang ◽

Y. Peng ◽

Y. Xu ◽

J. Zheng

Keyword(s):

Eastern China ◽

Summer Precipitation ◽

Internal Variability ◽

Last Millennium ◽

Model Data ◽

Proxy Data ◽

The Past ◽

Temperature Regimes ◽

Temporal And Spatial Variability ◽

Temporal And Spatial

Abstract. We use measurements of recent decades, 1500-yr proxy data, and millennium model simulations with a variety of climate facings to study the temporal and spatial variability of summer precipitation over eastern China. Spectral analysis of the proxy data using multi-taper method reveals three statistically significant bidecadal (15–35-yr), pendadecadal (40–60-yr), and centennial (65–170-yr) oscillation bands. The results of wavelet filtering show that the amplitudes of these bands vary substantially through time depending on the temperature regimes. Weak centennial oscillation and strong pentadecadal oscillation occur in warm conditions, whereas both the centennial and pentadecadal oscillations are strong in cold conditions. A model/data intercomparison suggests that pentadecadal and bidecadal oscillations could be associated with internal variability of the climate system. It is also found that the increased frequency of drought-in-north/flood-in-south spatial pattern over eastern China during the last two decades is unusual in the past five centuries.

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Was the Little Ice Age more or less El Niño-like than the Medieval Climate Anomaly? Evidence from hydrological and temperature proxy data

Climate of the Past ◽

10.5194/cp-13-267-2017 ◽

2017 ◽

Vol 13 (3) ◽

pp. 267-301 ◽

Cited By ~ 13

Author(s):

Lilo M. K. Henke ◽

F. Hugo Lambert ◽

Dan J. Charman

Keyword(s):

Little Ice Age ◽

Large Scale ◽

Global Climate ◽

Ice Age ◽

Medieval Climate Anomaly ◽

Climate Anomaly ◽

Proxy Data ◽

The Past ◽

Proxy Records

Abstract. The El Niño–Southern Oscillation (ENSO) is the most important source of global climate variability on interannual timescales and has substantial environmental and socio-economic consequences. However, it is unclear how it interacts with large-scale climate states over longer (decadal to centennial) timescales. The instrumental ENSO record is too short for analysing long-term trends and variability and climate models are unable to accurately simulate past ENSO states. Proxy data are used to extend the record, but different proxy sources have produced dissimilar reconstructions of long-term ENSO-like climate change, with some evidence for a temperature–precipitation divergence in ENSO-like climate over the past millennium, in particular during the Medieval Climate Anomaly (MCA; AD ∼  800–1300) and the Little Ice Age (LIA; AD ∼  1400–1850). This throws into question the stability of the modern ENSO system and its links to the global climate, which has implications for future projections. Here we use a new statistical approach using weighting based on empirical orthogonal function (EOF) to create two new large-scale reconstructions of ENSO-like climate change derived independently from precipitation proxies and temperature proxies. The method is developed and validated using model-derived pseudo-proxy experiments that address the effects of proxy dating error, resolution, and noise to improve uncertainty estimations. We find no evidence that temperature and precipitation disagree over the ENSO-like state over the past millennium, but neither do they agree strongly. There is no statistically significant difference between the MCA and the LIA in either reconstruction. However, the temperature reconstruction suffers from a lack of high-quality proxy records located in ENSO-sensitive regions, which limits its ability to capture the large-scale ENSO signal. Further expansion of the palaeo-database and improvements to instrumental, satellite, and model representations of ENSO are needed to fully resolve the discrepancies found among proxy records and establish the long-term stability of this important mode of climatic variability.

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SEDIMEN LAUT SEBAGAI PROXY DALAM MENENTUKAN DINAMIKA IKLIM DI MASA LAMPAU

OSEANA ◽

10.14203/oseana.2018.vol.43no.3.58 ◽

2018 ◽

Vol 43 (3) ◽

pp. 1-15

Author(s):

Septriono Hari Nugroho

Keyword(s):

Climate Change ◽

Calcium Carbonate ◽

Marine Sediment ◽

Isotope Composition ◽

Climatic Conditions ◽

Climate Dynamics ◽

Quantitative Interpretation ◽

Proxy Data ◽

Paleoclimate Reconstruction ◽

The Past

MARINE SEDIMENT AS PROXY TO DETERMINE CLIMATE DYNAMICS IN THE PAST. Studying the dynamics of climate change in the past is important and necessary, because it can serve as a basis for understanding the modern climate and the causes of its variations and changes. Evidence of past climatic conditions is usually archived on traces in nature that provide a proxy of past climatic conditions that we can explore. One of the major sources of proxy data for paleoclimate reconstruction is marine sediment. Microfossils usually used for quantitative proxy is foraminifer, diatom, pollen and etc. For the purposes of paleoclimate, the most important material is foraminifera. The paleoclimate results from the remains of carbonate and silica organisms have been generated from four types of analyzes: (a) oxygen isotope composition, especially calcium carbonate in foraminifer test (b) quantitative interpretation of species and its spatial variation through (c) the ratio of Mg / Ca to the foram test, which is related to temperature, and (d) the morphological variation in certain species resulting from environmental factors.

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Reconstructing the Evolution of Ice Sheets, Sea Level and Atmospheric CO<sub>2</sub> During the Past 3.6 Million Years

10.5194/cp-2020-52 ◽

2020 ◽

Cited By ~ 1

Author(s):

Constantijn J. Berends ◽

Bas de Boer ◽

Roderik S. W. van de Wal

Keyword(s):

Sea Level ◽

Climate Model ◽

Ice Sheets ◽

Early Pleistocene ◽

Geological Time ◽

Glacial Cycles ◽

Proxy Data ◽

Late Pliocene ◽

Ice Volume ◽

The Past

Abstract. Understanding the evolution of, and the interactions between, ice sheets and the global climate over geological time is important for being able to constrain earth system sensitivity. However, direct observational evidence of past CO2 concentrations only exists for the past 800 000 years. Records of benthic δ18O date back millions of years, but contain signals from both land ice volume and ocean temperature. In recent years, inverse forward modelling has been developed as a method to disentangle these two signals, resulting in mutually consistent reconstructions of ice volume, temperature and CO2. We use this approach to force a hybrid ice-sheet – climate model with a benthic δ18O stack, reconstructing the evolution of the ice sheets, global mean sea level and atmospheric CO2 during the late Pliocene and the Pleistocene, from 3.6 million years (Myr) ago to the present day. During the warmer-than-present climates of the Late Pliocene, reconstructed CO2 varies widely, from 320–440 ppmv for warm periods such as Marine Isotope Stage (MIS) KM5c, to 235–250 ppmv for the MIS M2 glacial excursion. Sea level is relatively stable during this period, with a high stand of 6–14 m, and a drop of 12–26 m during MIS M2. Both CO2 and sea level are within the wide ranges of values covered by available proxy data for this period. Our results for the Pleistocene agree well with the ice-core CO2 record, as well as with different available sea-level proxy data. During the early Pleistocene, 2.6–1.2 Myr ago, we simulate 40 kyr glacial cycles, with interglacial CO2 decreasing from 280–300 ppmv at the beginning of the Pleistocene, to 250–280 ppmv just before the Mid-Pleistocene Transition (MPT). Peak glacial CO2 decreases from 220–250 ppmv to 205–225 ppmv during this period. After the MPT, when the glacial cycles change from 40 kyr to 80/120 kyr cyclicity, the glacial-interglacial contrast increases, with interglacial CO2 varying between 250–320 ppmv, and peak glacial values decreasing to 170–210 ppmv.

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Variability of summer precipitation over eastern China during the last millennium

Climate of the Past Discussions ◽

10.5194/cpd-4-611-2008 ◽

2008 ◽

Vol 4 (3) ◽

pp. 611-643 ◽

Cited By ~ 4

Author(s):

C. Shen ◽

W.-C. Wang ◽

Y. Peng ◽

Y. Xu ◽

J. Zheng

Keyword(s):

Eastern China ◽

Summer Precipitation ◽

Internal Variability ◽

Model Data ◽

Solar Forcing ◽

Proxy Data ◽

The Past ◽

Temperature Regimes ◽

Temporal And Spatial Variability ◽

Temporal And Spatial

Abstract. We use measurements of recent decades, 1500-yr proxy data, and millennium model simulations with a variety of climate facings to study the temporal and spatial variability of summer precipitation over eastern China. Spectral analysis of the proxy data using multi-taper method reveals three statistically significant bidecadal (15–35-yr), pendadecadal (40–60-yr), and centennial (65–170-yr) oscillation bands. The results of wavelet filtering show that the amplitudes of these bands vary substantially through time depending on the temperature regimes. Weak centennial oscillation and strong pentadecadal oscillation occur in warm conditions, whereas the oscillations are both strong in cold conditions. A model/data intercomparison suggests that the centennial oscillation might be linked to the fluctuation of solar forcing (Gleissberg cycle), and the pentadecadal and bidecadal oscillations could be associated with internal variability of the climate system. It is also found that the increased frequency of drought-in-north/flood-in-south spatial pattern over eastern China during the last two decades is unusual in the past five centuries.

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Characteristics of cold-warm variation in the Hetao region and its surrounding areas in China during the past 5000 yr

Climate of the Past Discussions ◽

10.5194/cpd-6-1-2010 ◽

2010 ◽

Vol 6 (1) ◽

pp. 1-18

Author(s):

M. Li ◽

Q. Ge ◽

Z. Hao ◽

J. Zheng ◽

S. He

Keyword(s):

Climate Changes ◽

Mean Value ◽

Data Series ◽

Proxy Data ◽

Average Temperature ◽

The Past ◽

The Mean ◽

Temperature Proxy ◽

Surrounding Areas

Abstract. Using six long-term temperature proxy data series derived from different natural evidences, including pollens and lake-sediments, we reconstructed a temperature series with a 100-year time resolution for the past 5000 yr in the Hetao region and its surrounding areas. The resulting series suggests that, on a millennial timescale, temperatures in the region were higher than the mean value of the whole series during the 5000~2600 yr before present (yr BP) period, and became relatively low comparing with the average temperature of the whole series after 2600 yr BP. Within these two periods, temperature fluctuations comprising numerous short, multi-centennial intervals also existed. A comparison between our reconstructed series and other series in China and across the Northern Hemisphere indicate that, on a long-term scale, cold–warm variations had been in phase across the whole hemisphere during the past 5000 yr; on the century to multi-century scale, the beginning and the ending times varied from region to region, thus implying that climate changes did not occur simultaneously in different regions.

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The Paleoclimate reanalysis project

Climate of the Past Discussions ◽

10.5194/cpd-11-4159-2015 ◽

2015 ◽

Vol 11 (5) ◽

pp. 4159-4204 ◽

Cited By ~ 2

Author(s):

S. A. Browning ◽

I. D. Goodwin

Keyword(s):

Data Assimilation ◽

World View ◽

Internal Variability ◽

Temporal Variations ◽

Global Ocean ◽

Model Data ◽

Proxy Data ◽

The Past ◽

Spatial Fields ◽

Past Millennium

Abstract. Recent advances in proxy-model data assimilation have made feasible the development of proxy-based reanalyses. Proxy-based reanalyses aim to make optimum use of both proxy and model data while presenting paleoclimate information in an accessible format – they will undoubtedly play a pivotal role in the future of paleoclimate research. In the Paleoclimate Reanalysis Project (PaleoR) we use "off-line" data assimilation to constrain the CESM1 (CAM5) Last Millennial Ensemble (LME) simulation with a globally distributed multivariate proxy dataset, producing a decadal resolution reanalysis of the past millennium. Discrete time periods are "reconstructed" by using anomalous (±0.5σ) proxy climate signals to select an ensemble of climate state analogues from the LME. Prior to assimilation the LME simulates internal variability that is temporally inconsistent with information from the proxy archive. After assimilation the LME is highly correlated to almost all included proxy data, and dynamical relationships between modelled variables are preserved; thus providing a "real-world" view of climate system evolution during the past millennium. Unlike traditional regression based approaches to paleoclimatology, PaleoR is unaffected by temporal variations in teleconnection patterns. Indices representing major modes of global ocean–atmosphere climate variability can be calculated directly from PaleoR spatial fields. PaleoR derived ENSO, SAM, and NAO indices are consistent with observations and published multiproxy reconstructions. The computational efficiency of "off-line" data assimilation allows easy incorporation and evaluation of new proxy data, and experimentation with different setups and model simulations. PaleoR spatial fields can be viewed online at http://climatefutures.mq.edu.au/research/themes/marine/paleor/.

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