HUMANPAST.NET

Environment                  60,000 BC
Africa
Southwest Asia
Egypt
Indus Valley
China
Europe
South America
Mesoamerica
North America
Other

In General

What is now clear is that during the last ice age, and the period that followed it, the climate was much more chaotic than it has been in recent millennia. Generally, the climate was much more variable. Sudden changes occurred from time to time. Collapse of parts of the ice sheets, or release of meltwater lakes that built up behind the ice, led to cataclysmic changes. Armadas of icebergs or floods of icy freshwater swept out into the North Atlantic altering the circulation of the ocean at a stroke and with it the climate of the neighbouring continents. With a flick of the climatic switch, Europe and much of North America could be plunged back into icy conditions, having only just emerged from the abyss of the preceding millennia. Conversely, the stability of the glacial conditions could be interrupted by a re-establishment of the flow of warm water to higher latitudes in the North Atlantic, bringing surprising temporary warmth to the northern continents. (145)

...the isotopic temperature records show some 20 interstadials, ...between 15 and 100 kya. Typically the events start with an abrupt warming of Greenland of some 5 to 10°C over a few decades or less. This warming is followed by a gradual cooling over several hundred years, and occasionally much longer. This cooling phase often ends with an abrupt final reduction of temperature back to cold ('stadial') conditions. (145)

The truly notable feature is the additional emphasis given to the prolonged cold period from 70 to 63 kya, to the cold spell at around 36 kya and to the frequency of extreme cold from 30 to 15 kya. (145)

Changes in the sea level during the last 100 kyr. (145)

It is a curious coincidence of geology and palaeoanthropology that the onset and progress of the last Ice Age, and the emergence and proliferation of modern Man, more or less shadow each other. Curious too is the fact that so little is known about either. The crucial stages of Ice Age chronology thus appear to be: 1 around 60,000 years ago, when the Wurm, the Wisconsin and other glaciations were well under way; 2 around 17,000 years ago, when the ice sheets had reached their maximum extent in both the Old World and the New; 3 the 7000 years of deglaciation that followed. (152

Africa

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Southwest Asia

 In Israel a detailed lake-level history of the closed Lake Lisan (part of the ancient Dead Sea) indicates that for much of the period from 55 kya to the end of the ice age the level was higher than at present. There were, however, catastrophic droughts associated with the Heinrich events. The impression is that cold-water input to the Mediterranean originating in the collapse of North Atlantic Deep Water formation caused a reduction of evaporation and less precipitation in the Levant. So it is reasonable to conclude that following Heinrich events 6, 5, and 3 much of the Middle East was desert. During these intervals, of which the long cold period from around 67 to 59 kya was the most significant, the region was largely uninhabitable for modern humans. (145)

Egypt

 

Indus Valley

 

China

 

Europe

  By 75,000 years ago glacial conditions had begun in Europe, and a great ice sheet formed, perhaps on a land bridge connecting the British Isles with Iceland and Greenland. After a few thousand years it had grown thick enough to move out from the center of thickest accumulation by gravity. It covered Ireland, filled the Irish Sea basin and swept across the Welsh mountains into England about 55,000 years ago. Its advance, it appears, required a period of 20,000 to 25,000 years, comparable to the time that was apparently required for the growth of the Wisconsin ice sheet. ...a polar shift occurred at about the time this ice sheet reached its maximum: the shift from the Greenland Sea to Hudson Bay. It is easy to connect the two events: The shift brought the advance to an end and initiated the glacial retreat. This retreat probably started long before 42,000 years ago, and by about 37,000 years ago the ice sheet had left the Irish Sea basin. The decline of the Irish Sea ice sheet seems to have required a period of time similar to the time required for the decline of the Wisconsin ice sheet. The parallel is extremely interesting. (132)

Recent absolutely dated speleothem results from southwestern France show an intensely cold period extending from 67.4 to 61.2 kya. Here it is estimated that the average temperature dropped by 13.6°C between 75 kya and 67 kya. The speleothem then stopped growing until 61 kya, presumably because permafrost formed above the cave. (145)

South America

 

Mesoamerica

 

North America

Today, Eskimos using skin boats easily cross the ninety kilometers of open sea separating Siberia and America, and recently an American woman slathered herself with grease and actually swam from Alaska to Siberia. But such a sea crossing would not have been necessary during much of the Pleistocene. During periods of glacial advance within the last million years, enourmous quantities of water were converted to ice, lowering the sea level sufficiently to expose a 1500- to 3000-kilometer-wide expanse of the floor of the Bering Sea. This land bridge--usually referred to as Beringia--was probably available at least four times in the last 60,000 years.(25)

Prior to 10,000 years ago, species of deer, bison,camels, bears, foxes, mammoths, moose, caribou,and even rodents crossed from Siberia into the New World. Going in the other way--from America to Asia--were foxes, woodchucks, and, during the early Pliestocene, the ancestors of modern forms of horses, wolves, and other animals.(25)

Interior Alaska and Canada were relatively rich environments in the mid-Wisconsin interglacial, and at times humans may have had a narrow but clear ice-free run all the way to South America during this period. Pollen cores from easternmost Beringia suggest that from 30,000 to 14,000 years ago, the time when most archeologists think the first Americans arrived, the "landscape of Beringia consisted of relatively bare polar desert or fell-field tundra, a rocky terrain sparsely vegetated by herbs and dwarf shrubs. This suggests that the late Wisconsin environment in this part of Beringia was as harsh as the modern high Arctic.(25)

Several lines of solid evidence suggest that during the last ice age the North Pole was located in or near Hudson Bay. ...the best guess for the site of the pole seems to be approximately 60 degrees North Latitude and 83 degrees West Longitude. The first line of evidence that the last North American ice cap was a polar ice cap is based on the shape, size, and peculiar geographical location of the ice sheet. (132)

Studies of stalagmites from a cave in southeastern Missouri show remarkably little variation after a marked cooling around 55 kya. Prior to this, conditions appear to have oscillated more frequently. The warmest temperatures occurred around 57 kya and there were short-lived cooling events around 64, 71 and 74 kya. Beetle assemblages suggest that, following the cooling around 55 kya, the mean July temperature was 7.5-8°C lower than present and mean January value was 15-18°C lower than present. During what is termed the 'mid-Wisconsin' interstadial, dating from 43.5 to 39 kya, there was a rapid and intense warming. At the peak of this event, about 42kya, July temperatures were only 1-2°C lower than modern. (145)

Other

 Around the time of the onset of OIS3 the Australian climate entered a wetter phase. These moister conditions prevailed until around 40 kya, with only occasional drier periods lasting up to a millennium, although there is evidence of an increasing incidence of dry periods towards the end of this period. Then the climate became much more arid. The transition to increasing aridity appears to have coincided with the arrival of humans in Australia, which is now estimated to have been around 60kya. (145)