Spread of Farming, New Diseases, and Rising Civilizations: Mid- Holocene Optimum

2017 ◽  
Author(s):  
Anthony McMichael
Keyword(s):  
Northern Hemisphere ◽  
Social Relations ◽  
Cultural Practices ◽  
Close Contact ◽  
Ice Sheets ◽  
Sun Exposure ◽  
Human Populations ◽  
The Earth ◽  
Maximum Temperatures ◽  
Earth’S Climate

As The Earth Warmed after the last glacial maximum, temperatures fluctuated. About 9700 B.C.E., temperatures rose again suddenly and began to stabilize, marking the beginning of a new geological epoch, the Holocene. The landscape continued to change, but not so fast that a single generation of humans would have noticed. Ice- sheets and tundra were receding in Eurasia, and over time human groups, both hunter- gatherers and then early farmer- pastoralist communities, adjusted their ways of living to warmer conditions and different rainfall patterns. Small- scale farming and herding emerged on all nonpolar con­tinents during the period 8500 to 6000 B.C.E., predominantly in the northern hemisphere, while human numbers were creeping up. These great changes in environmental conditions and subsequent cultural practices had a profound influence on the foundations of human health and survival: food sufficiency and quality, water sup­plies, contacts with infectious agents, modes of settlement, and social relations. A new era in human ecology was looming. Farming increased food production, but the switch to dependency on a few staples decreased diversity of diets and created an annual agricul­tural regime more susceptible to climate shifts. Close contact with animals, standing water in irrigated environments, and denser set­tlements provided opportunities for microbes, pathogens, viruses, and parasites to cross species barriers and infect and spread among human populations. During the Early Holocene, from about 9700 B.C.E. to 6000 B.C.E., the earth was subjected to the competing stresses of high solar influ­ence and still massive melting ice- sheets. From around 6000 B.C.E., the majority of ice- sheet melting had abated, allowing the stabiliza­tion of the Earth’s climate into what can be called the Mid- Holocene Climatic Optimum (approx. 6000 to 3000 B.C.E.). This was a change in climate that spanned 3,000 to 4,000 years. Warming was most evi­dent in the northern hemisphere, influenced by the peaking of solar radiation at higher northern latitudes as the 23,000- year Milankovitch “wobble” cycle maximized northern sun exposure for several millen­nia. The Milankovitch cycle also drew the rain- bearing Inter- Tropical Convergence Zone (ITCZ) further north.

scholarly journals Snowfall-albedo feedbacks could have led to deglaciation of snowball Earth starting from mid-latitudes

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Philipp de Vrese ◽  
Tobias Stacke ◽  
Jeremy Caves Rugenstein ◽  
Jason Goodman ◽  
Victor Brovkin
Keyword(s):  
Carbon Dioxide ◽  
Atmospheric Carbon Dioxide ◽  
Climate Models ◽  
Hydrological Cycle ◽  
High Surface ◽  
Dust Deposition ◽  
Carbon Dioxide Concentrations ◽  
Maximum Temperatures ◽  
Carbon Dioxide Levels ◽  
Earth’S Climate

AbstractSimple and complex climate models suggest a hard snowball – a completely ice-covered planet – is one of the steady-states of Earth’s climate. However, a seemingly insurmountable challenge to the hard-snowball hypothesis lies in the difficulty in explaining how the planet could have exited the glaciated state within a realistic range of atmospheric carbon dioxide concentrations. Here, we use simulations with the Earth system model MPI-ESM to demonstrate that terminal deglaciation could have been triggered by high dust deposition fluxes. In these simulations, deglaciation is not initiated in the tropics, where a strong hydrological cycle constantly regenerates fresh snow at the surface, which limits the dust accumulation and snow aging, resulting in a high surface albedo. Instead, comparatively low precipitation rates in the mid-latitudes in combination with high maximum temperatures facilitate lower albedos and snow dynamics that – for extreme dust fluxes – trigger deglaciation even at present-day carbon dioxide levels.

scholarly journals Investigating the evolution of major Northern Hemisphere ice sheets during the last glacial-interglacial cycle

2009 ◽  
Vol 5 (3) ◽  
pp. 329-345 ◽  
Author(s):  
S. Bonelli ◽  
S. Charbit ◽  
M. Kageyama ◽  
M.-N. Woillez ◽  
G. Ramstein ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Climate Model ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Co2 Concentration ◽  
Atmospheric Co2 ◽  
Glacial Cycle ◽  
Last Glacial ◽  
Atmospheric Co2 Concentration ◽  
The Last Glacial

Abstract. A 2.5-dimensional climate model of intermediate complexity, CLIMBER-2, fully coupled with the GREMLINS 3-D thermo-mechanical ice sheet model is used to simulate the evolution of major Northern Hemisphere ice sheets during the last glacial-interglacial cycle and to investigate the ice sheets responses to both insolation and atmospheric CO2 concentration. This model reproduces the main phases of advance and retreat of Northern Hemisphere ice sheets during the last glacial cycle, although the amplitude of these variations is less pronounced than those based on sea level reconstructions. At the last glacial maximum, the simulated ice volume is 52.5×1015 m3 and the spatial distribution of both the American and Eurasian ice complexes is in reasonable agreement with observations, with the exception of the marine parts of these former ice sheets. A set of sensitivity studies has also been performed to assess the sensitivity of the Northern Hemisphere ice sheets to both insolation and atmospheric CO2. Our results suggest that the decrease of summer insolation is the main factor responsible for the early build up of the North American ice sheet around 120 kyr BP, in agreement with benthic foraminifera δ18O signals. In contrast, low insolation and low atmospheric CO2 concentration are both necessary to trigger a long-lasting glaciation over Eurasia.

scholarly journals Aging Human Populations: Good for Us, Good for the Earth

2018 ◽  
Vol 33 (11) ◽  
pp. 851-862 ◽  
Author(s):  
Frank Götmark ◽  
Philip Cafaro ◽  
Jane O’Sullivan
Keyword(s):  
Human Populations ◽  
The Earth ◽  
Good For

Investigating the mechanisms leading to the deglaciation of past continental northern hemisphere ice sheets with the CLIMBER–GREMLINS coupled model

2005 ◽  
Vol 48 (4) ◽  
pp. 253-273 ◽  
Author(s):  
Sylvie Charbit ◽  
Masa Kageyama ◽  
Didier Roche ◽  
Catherine Ritz ◽  
Gilles Ramstein
Keyword(s):  
Northern Hemisphere ◽  
Ice Sheets ◽  
Coupled Model

scholarly journals Influence of ablation-related processes in the built-up of simulated Northern Hemisphere ice sheets during the last glacial cycle

2012 ◽  
Vol 6 (6) ◽  
pp. 4897-4938 ◽  
Author(s):  
S. Charbit ◽  
C. Dumas ◽  
M. Kageyama ◽  
D. M. Roche ◽  
C. Ritz
Keyword(s):  
Northern Hemisphere ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Glacial Cycle ◽  
Satisfactory Description ◽  
Last Glacial ◽  
Transient Simulations ◽  
Main Driver ◽  
The Impact ◽  
The Last Glacial

Abstract. Since the original formulation of the positive-degree-day (PDD) method, different PDD calibrations have been proposed in the literature in response to the increasing number of observations. Although these formulations provide a satisfactory description of the present-day Greenland geometry, they have not all been tested for paleo ice sheets. Using the climate-ice sheet model CLIMBER-GRISLI coupled with different PDD models, we evaluate how the parameterization of the ablation may affect the evolution of Northern Hemisphere ice sheets in the transient simulations of the last glacial cycle. Results from fully coupled simulations are compared to time-slice experiments carried out at different key periods of the last glacial period. We find large differences in the simulated ice sheets according to the chosen PDD model. These differences occur as soon as the onset of glaciation, therefore affecting the subsequent evolution of the ice system. To further investigate how the PDD method controls this evolution, special attention is given to the role of each PDD parameter. We show that glacial inception is critically dependent on the representation of the impact of the temperature variability from the daily to the inter-annual time scale, whose effect is modulated by the refreezing scheme. Finally, an additional set of sensitivity experiments has been carried out to assess the relative importance of melt processes with respect to initial ice sheet configuration in the construction and the evolution of past Northern Hemisphere ice sheets. Our analysis reveals that the impacts of the initial ice sheet condition may range from quite negligible to explaining about half of the LGM ice volume depending on the representation of stochastic temperature variations which remain the main driver of the evolution of the ice system.

scholarly journals Mode transitions in Northern Hemisphere Glaciation: Co-evolution of millennial and orbital variability in Quaternary climate

2016 ◽  
Author(s):  
David A. Hodell ◽  
James E.T. Channell
Keyword(s):  
Climate Variability ◽  
Northern Hemisphere ◽  
North Atlantic ◽  
Ice Sheets ◽  
Deep Ocean ◽  
Progressive Increase ◽  
The North ◽  
Quaternary Climate ◽  
Mode Transitions ◽  
Millennial Scale

Abstract. We present a 3.2-Myr record of stable isotopes and physical properties at IODP Site U1308 (re-occupation of DSDP Site 609) located within the ice-rafted detritus (IRD) belt of the North Atlantic. We compare the isotope and lithological proxies at Site U1308 with other North Atlantic records (e.g., Sites 982, 607/U1313 and U1304) to reconstruct the history of orbital and millennial-scale climate variability during the Quaternary. The Site U1308 record documents a progressive increase in the intensity of Northern Hemisphere glacial-interglacial cycles during the late Pliocene and Quaternary with mode transitions at ~ 2.7, 1.5, 0.9 and 0.65 Ma. These transitions mark times of change in the growth and stability of Northern Hemisphere ice sheets. They also coincide with increases in vertical carbon isotope gradients between the intermediate and deep ocean, suggesting changes in deep carbon storage and atmospheric CO2. Orbital and millennial climate variability co-evolved during the Quaternary such that the trend towards larger ice sheets was accompanied by changes in the style, frequency and intensity of millennial-scale variability. This co-evolution may be important for explaining the observed patterns of Quaternary climate change.

scholarly journals Keep That Lane Open!: Race, Space, and Mardi Gras in Kansas City

2017 ◽  
Vol 11 (1-2) ◽  
Author(s):  
Peter A. Williams
Keyword(s):  
New Orleans ◽  
Urban Space ◽  
Social Relations ◽  
Kansas City ◽  
Cultural Practices ◽  
Historical Narrative ◽  
African American Culture ◽  
Mardi Gras ◽  
Cultural Form ◽  
Bodily Movement

This essay explores the open-ended and complex performance of an underground Mardi Gras parade in Kansas City, MO, in 2012. The sounds, movement, and route of the parade are shaped by a network of globally circulating images of Mardi Gras in New Orleans, the history of race and space in Kansas City, and the intercultural exchange involved in white performances of black cultural practices as they move from the “circum-Caribbean” city of New Orleans to the U.S. heartland of Kansas City. The parade is a partially improvised performance of a historical narrative linking Kansas City’s mostly white bohemian arts culture in the present to the city’s past as a major jazz city and center for African American culture. This narrative is told by bodily movement through urban space and through improvised sound and dance, and demonstrates the complex social relations that are highlighted when a cultural form is subject to cross-cultural communication, borrowing, and appropriation.

Effects of Continents and Supercontinents on Climate

2004 ◽  
Author(s):  
John J. W. Rogers ◽  
M. Santosh
Keyword(s):  
Global Climate ◽  
Climatic Conditions ◽  
Polar Regions ◽  
The North ◽  
Rock Types ◽  
Control Climate ◽  
The Earth ◽  
History Of ◽  
Earth’S Climate ◽  
Geologic Record

Continents affect the earth’s climate because they modify global wind patterns, control the paths of ocean currents, and absorb less heat than seawater. Throughout earth history the constant movement of continents and the episodic assembly of supercontinents has influenced both global climate and the climates of individual continents. In this chapter we discuss both present climate and the history of climate as far back in the geologic record as we can draw inferences. We concentrate on longterm changes that are affected by continental movements and omit discussion of processes with periodicities less than about 20,000 years. We refer readers to Clark et al. (1999) and Cronin (1999) if they are interested in such short-term processes as El Nino, periodic variations in solar irradiance, and Heinrich events. The chapter is divided into three sections. The first section describes the processes that control climate on the earth and includes a discussion of possible causes of glaciation that occurred over much of the earth at more than one time in the past. The second section investigates the types of evidence that geologists use to infer past climates. They include specific rock types that can form only under restricted climatic conditions, varieties of individual fossils, diversity of fossil populations, and information that the 18O/16O isotopic system can provide about temperatures of formation of ancient sediments. The third section recounts the history of the earth’s climate and relates changes to the growth and movement of continents. This history takes us from the Archean, when climates are virtually unknown, through various stages in the evolution of organic life, and ultimately to the causes of the present glaciation in both the north and the south polar regions. The earth’s climate is controlled both by processes that would operate even if continents did not exist and also by the positions and topographies of continents. We begin with the general controls, then discuss the specific effects of continents, and close with a brief discussion of processes that cause glaciation. The general climate of the earth is determined by the variation in the amount of sunshine received at different latitudes, by the earth’s rotation, and by the amount of arriving solar energy that is retained in the atmosphere.

scholarly journals Paleocene/Eocene carbon feedbacks triggered by volcanic activity

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Sev Kender ◽  
Kara Bogus ◽  
Gunver K. Pedersen ◽  
Karen Dybkjær ◽  
Tamsin A. Mather ◽  
...  
Keyword(s):  
North Atlantic ◽  
Proxy Records ◽  
The North ◽  
The Earth ◽  
Thermal Maximum ◽  
Igneous Province ◽  
Carbon Release ◽  
Carbon Reservoir ◽  
Earth’S Climate ◽  
North Atlantic Igneous Province

AbstractThe Paleocene–Eocene Thermal Maximum (PETM) was a period of geologically-rapid carbon release and global warming ~56 million years ago. Although modelling, outcrop and proxy records suggest volcanic carbon release occurred, it has not yet been possible to identify the PETM trigger, or if multiple reservoirs of carbon were involved. Here we report elevated levels of mercury relative to organic carbon—a proxy for volcanism—directly preceding and within the early PETM from two North Sea sedimentary cores, signifying pulsed volcanism from the North Atlantic Igneous Province likely provided the trigger and subsequently sustained elevated CO2. However, the PETM onset coincides with a mercury low, suggesting at least one other carbon reservoir released significant greenhouse gases in response to initial warming. Our results support the existence of ‘tipping points’ in the Earth system, which can trigger release of additional carbon reservoirs and drive Earth’s climate into a hotter state.

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