scholarly journals Centennial Variations of the Global Monsoon Precipitation in the Last Millennium: Results from ECHO-G Model

2009 ◽  
Vol 22 (9) ◽  
pp. 2356-2371 ◽  
Author(s):  
Jian Liu ◽  
Bin Wang ◽  
Qinghua Ding ◽  
Xueyuan Kuang ◽  
Willie Soon ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Carbon Dioxide Concentration ◽  
Medieval Warm Period ◽  
Forced Response ◽  
Warm Period ◽  
Ice Age ◽  
Last Millennium ◽  
Solar Forcing ◽  
Global Monsoon ◽  
Northern And Southern Hemispheres

Abstract The authors investigate how the global monsoon (GM) precipitation responds to the external and anthropogenic forcing in the last millennium by analyzing a pair of control and forced millennium simulations with the ECHAM and the global Hamburg Ocean Primitive Equation (ECHO-G) coupled ocean–atmosphere model. The forced run, which includes the solar, volcanic, and greenhouse gas forcing, captures the major modes of precipitation climatology comparably well when contrasted with those captured by the NCEP reanalysis. The strength of the modeled GM precipitation in the forced run exhibits a significant quasi-bicentennial oscillation. Over the past 1000 yr, the simulated GM precipitation was weak during the Little Ice Age (1450–1850) with the three weakest periods occurring around 1460, 1685, and 1800, which fell in, respectively, the Spörer Minimum, Maunder Minimum, and Dalton Minimum periods of solar activity. Conversely, strong GM was simulated during the model Medieval Warm Period (ca. 1030–1240). Before the industrial period, the natural variations in the total amount of effective solar radiative forcing reinforce the thermal contrasts both between the ocean and continent and between the Northern and Southern Hemispheres resulting in the millennium-scale variation and the quasi-bicentennial oscillation in the GM index. The prominent upward trend in the GM precipitation occurring in the last century and the notable strengthening of the global monsoon in the last 30 yr (1961–90) appear unprecedented and are due possibly in part to the increase of atmospheric carbon dioxide concentration, though the authors’ simulations of the effects from recent warming may be overestimated without considering the negative feedbacks from aerosols. The simulated change of GM in the last 30 yr has a spatial pattern that differs from that during the Medieval Warm Period, suggesting that global warming that arises from the increases of greenhouse gases and the input solar forcing may have different effects on the characteristics of GM precipitation. It is further noted that GM strength has good relational coherence with the temperature difference between the Northern and Southern Hemispheres, and that on centennial time scales the GM strength responds more directly to the effective solar forcing than the concurrent forced response in global-mean surface temperature.

scholarly journals The origin of the European "Medieval Warm Period"

2006 ◽  
Vol 2 (2) ◽  
pp. 99-113 ◽  
Author(s):  
H. Goosse ◽  
O. Arzel ◽  
J. Luterbacher ◽  
M. E. Mann ◽  
H. Renssen ◽  
...  
Keyword(s):  
Land Use ◽  
20Th Century ◽  
Climate Model ◽  
Land Use Changes ◽  
Medieval Warm Period ◽  
Forced Response ◽  
Warm Period ◽  
Ice Age ◽  
Climate History ◽  
Proxy Records

Abstract. Proxy records and results of a three dimensional climate model show that European summer temperatures roughly a millennium ago were comparable to those of the last 25 years of the 20th century, supporting the existence of a summer "Medieval Warm Period" in Europe. Those two relatively mild periods were separated by a rather cold era, often referred to as the "Little Ice Age". Our modelling results suggest that the warm summer conditions during the early second millennium compared to the climate background state of the 13th–18th century are due to a large extent to the long term cooling induced by changes in land-use in Europe. During the last 200 years, the effect of increasing greenhouse gas concentrations, which was partly levelled off by that of sulphate aerosols, has dominated the climate history over Europe in summer. This induces a clear warming during the last 200 years, allowing summer temperature during the last 25 years to reach back the values simulated for the early second millennium. Volcanic and solar forcing plays a weaker role in this comparison between the last 25 years of the 20th century and the early second millennium. Our hypothesis appears consistent with proxy records but modelling results have to be weighted against the existing uncertainties in the external forcing factors, in particular related to land-use changes, and against the uncertainty of the regional climate sensitivity. Evidence for winter is more equivocal than for summer. The forced response in the model displays a clear temperature maximum at the end of the 20th century. However, the uncertainties are too large to state that this period is the warmest of the past millennium in Europe during winter.

scholarly journals Glacier maxima in Baffin Bay during the Medieval Warm Period coeval with Norse settlement

2015 ◽  
Vol 1 (11) ◽  
pp. e1500806 ◽  
Author(s):  
Nicolás E. Young ◽  
Avriel D. Schweinsberg ◽  
Jason P. Briner ◽  
Joerg M. Schaefer
Keyword(s):  
North Atlantic ◽  
Regional Climate ◽  
Medieval Warm Period ◽  
Warm Period ◽  
Ice Age ◽  
Last Millennium ◽  
North Atlantic Region ◽  
Atlantic Region ◽  
The North ◽  
The North Atlantic

The climatic mechanisms driving the shift from the Medieval Warm Period (MWP) to the Little Ice Age (LIA) in the North Atlantic region are debated. We use cosmogenic beryllium-10 dating to develop a moraine chronology with century-scale resolution over the last millennium and show that alpine glaciers in Baffin Island and western Greenland were at or near their maximum LIA configurations during the proposed general timing of the MWP. Complimentary paleoclimate proxy data suggest that the western North Atlantic region remained cool, whereas the eastern North Atlantic region was comparatively warmer during the MWP—a dipole pattern compatible with a persistent positive phase of the North Atlantic Oscillation. These results demonstrate that over the last millennium, glaciers approached their eventual LIA maxima before what is considered the classic LIA in the Northern Hemisphere. Furthermore, a relatively cool western North Atlantic region during the MWP has implications for understanding Norse migration patterns during the MWP. Our results, paired with other regional climate records, point to nonclimatic factors as contributing to the Norse exodus from the western North Atlantic region.

scholarly journals Climate Variability in Central Europe during the Last 2500 Years Reconstructed from Four High-Resolution Multi-Proxy Speleothem Records

Geosciences ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 166
Author(s):  
Sarah Waltgenbach ◽  
Dana F. C. Riechelmann ◽  
Christoph Spötl ◽  
Klaus P. Jochum ◽  
Jens Fohlmeister ◽  
...  
Keyword(s):  
Trace Elements ◽  
High Resolution ◽  
Climate Variability ◽  
Little Ice Age ◽  
Medieval Warm Period ◽  
Warm Period ◽  
Ice Age ◽  
Cold Period ◽  
Cave System ◽  
Dark Ages

The Late Holocene was characterized by several centennial-scale climate oscillations including the Roman Warm Period, the Dark Ages Cold Period, the Medieval Warm Period and the Little Ice Age. The detection and investigation of such climate anomalies requires paleoclimate archives with an accurate chronology as well as a high temporal resolution. Here, we present 230Th/U-dated high-resolution multi-proxy records (δ13C, δ18O and trace elements) for the last 2500 years of four speleothems from Bunker Cave and the Herbstlabyrinth cave system in Germany. The multi-proxy data of all four speleothems show evidence of two warm and two cold phases during the last 2500 years, which coincide with the Roman Warm Period and the Medieval Warm Period, as well as the Dark Ages Cold Period and the Little Ice Age, respectively. During these four cold and warm periods, the δ18O and δ13C records of all four speleothems and the Mg concentration of the speleothems Bu4 (Bunker Cave) and TV1 (Herbstlabyrinth cave system) show common features and are thus interpreted to be related to past climate variability. Comparison with other paleoclimate records suggests a strong influence of the North Atlantic Oscillation at the two caves sites, which is reflected by warm and humid conditions during the Roman Warm Period and the Medieval Warm Period, and cold and dry climate during the Dark Ages Cold period and the Little Ice Age. The Mg records of speleothems Bu1 (Bunker Cave) and NG01 (Herbstlabyrinth) as well as the inconsistent patterns of Sr, Ba and P suggests that the processes controlling the abundance of these trace elements are dominated by site-specific effects rather than being related to supra-regional climate variability.

scholarly journals Late Holocene climatic changes in Tierra del Fuego based on multiproxy analyses of peat deposits.

2004 ◽  
Vol 61 (2) ◽  
pp. 148-158 ◽  
Author(s):  
Dmitri Mauquoy ◽  
Maarten Blaauw ◽  
Bas van Geel ◽  
Ana Borromei ◽  
Mirta Quattrocchio ◽  
...  
Keyword(s):  
Fungal Spores ◽  
Plant Macrofossils ◽  
Medieval Warm Period ◽  
Warm Period ◽  
Tierra Del Fuego ◽  
Ice Age ◽  
Raised Bog ◽  
Climate Fluctuations ◽  
Peat Deposits ◽  
Tree Ring Data

A ca. 1400-yr record from a raised bog in Isla Grande, Tierra del Fuego, Argentina, registers climate fluctuations, including a Medieval Warm Period, although evidence for the ‘Little Ice Age’ is less clear. Changes in temperature and/or precipitation were inferred from plant macrofossils, pollen, fungal spores, testate amebae, and peat humification. The chronology was established using a 14C wiggle-matching technique that provides improved age control for at least part of the record compared to other sites. These new data are presented and compared with other lines of evidence from the Southern and Northern Hemispheres. A period of low local water tables occurred in the bog between A.D. 960–1020, which may correspond to the Medieval Warm Period date range of A.D. 950–1045 generated from Northern Hemisphere tree-ring data. A period of cooler and/or wetter conditions was detected between ca. A.D. 1030 and 1100 and a later period of cooler/wetter conditions estimated at ca. cal A.D. 1800–1930, which may correspond to a cooling episode inferred from Law Dome, Antarctica.

scholarly journals Vegetation changes in the Hotyn Upland over the last 2000 years (based on pollen data)

2019 ◽  
Vol 28 (1) ◽  
pp. 51-58 ◽  
Author(s):  
N. Gerasimenko ◽  
T. Yurchenko ◽  
Ye. Rohozin
Keyword(s):  
Little Ice Age ◽  
Environmental Changes ◽  
Medieval Warm Period ◽  
Warm Period ◽  
Ice Age ◽  
Humid Climate ◽  
Cool Period ◽  
Surface Samples ◽  
Pollen Surface ◽  
Short Period

Pollen study of two soil sections, located in two different relief positions (the gully bottom at Sadgora 1 and the upper part of a slope at Ridkivtsi I) enables us to show vegetational and climatic changes in the Bukovyna area (the Chernivtsi region) during the last 2000 years (the end of the Early Subatlantic, the Middle and Late Subatlantic). The reconstructions of past vegetation are based on the analyses of pollen surface samples, taken from the soils of different ecotops in the sites’ vicinity. The reconstructed short-period phases of environmental change correspond well with those established in other areas. These are the end of the “Roman warm period” (before the 14C date of 1.74 ka BP), with the humid climate; the relatively dry “Dark Ages cool period” (before the 14C date of 1.19 ka BP); the wet “Medieval warm period”; the cool “Little Ice Age” (with its wetter beginning and drier ending) and the modern warm phase (the last 150 years).Centennial environmental changes − the cooling within the Medieval Warming (XI cent.) and the warming within the “Little Ice Age” (XV cent.) – have been detected. Human impact on the vegetation can be demonstrated – forest clearance (with the presence of particles of microscopic charcoal and pollen of pyrophitic plants), the introduction of thermophilous walnut during warm periods, and the appearance of pasture lands in the place of former fern patches and woods during the “Little Ice Age”, and the last warm phase (with the presence of pollen of pastoral synanthropic plants). In the last 2000 years, broad-leaved woodland, dominated by hornbeam, grew extensively near Sadgora and Ridkivtsi only during the “Medieval Warm Period”.

The Little Ice Age and Medieval Warm Period in the Sargasso Sea

Science ◽  
1996 ◽  
Vol 274 (5292) ◽  
pp. 1503-1508 ◽  
Author(s):  
L. D. Keigwin
Keyword(s):  
Little Ice Age ◽  
Medieval Warm Period ◽  
Warm Period ◽  
Ice Age ◽  
Sargasso Sea

Geological records of changes in wind regime over south Greenland since the Medieval Warm Period: a tentative reconstruction

Polar Record ◽  
2009 ◽  
Vol 45 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Antoon Kuijpers ◽  
Naja Mikkelsen
Keyword(s):  
Atmospheric Circulation ◽  
Medieval Warm Period ◽  
Warm Period ◽  
Ice Age ◽  
East Greenland Current ◽  
Aeolian Deposits ◽  
New Information ◽  
North Atlantic Climate ◽  
Wind Activity ◽  
Marine Data

ABSTRACTPublished marine sediment core records and new information from terrestrial aeolian deposits from the surroundings of Igaliku Fjord, south Greenland, have been used for a tentative reconstruction of multi-decadal to centennial scale changes in the intensity of regional atmospheric circulation since the Medieval Warm Period. The marine data show that aeolian activity over southern Greenland was generally enhanced in the Medieval Warm Period between c. AD 900 and c. AD 1300. The preliminary data from the onshore aeolian deposits suggest that wind activity was strongest after AD 1000, reaching a peak close to AD 1300, after which atmospheric circulation intensity decreased. A comparison with the marine data shows that this decrease coincides with increased advection of Polar Water by the East Greenland Current at the beginning of the Little Ice Age. The aeolian sediment record suggests foehn wind activity displaying multi-decadal oscillations in the range of known north Atlantic climate oscillations. The intensity of erosional processes in south Greenland has previously often been attributed to farming activities initiated after AD 1000 by the Norse who disappeared a few hundred years later. Our findings suggest, however, that erosion in this area is mainly related to marked variations in wind strength.

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