Surviving The Ice Age, And Whatever Comes Next

  • Date: 18/08/15
  • Doug Hoffman, The Resilient Earth

Our ancestors survived the ups and downs of glacial period temperatures, as well as the heat of the Eemian interglacial. Bottom line: all this climate catastrophe hype is simply hot air. Humanity may go the way of the dodo but it will be for reasons other than the C02 we are putting into the atmosphere. Worrywarts look elsewhere, the rest of us can relax.

We have all heard about the Ice Age, if only in cartoon movies. A time when massive ice sheets covered the planet while mammoths and saber toothed cats roamed the frozen landscape. What is more, the cycle of interglacial-glacial-interglacial has happened over and over again during the past million or so years. During the last half a million years the cycle has repeated every 130,000 years, with the warm period we are now enjoying—the Holocene—just the latest interglacial respite from the icy conditions of the Pleistocene Ice Age. What most people don’t know is that there were many areas on Earth that remained unchanged, even during the height of the last glacial period. The Sahara was hot and dry, and in the Amazon rainforests, though a bit smaller in area, looked much like they do today.

The climate of our planet seems quite stable to us. The seasons come and go and some years are hotter or cooler than others, but in general there is no perceived drastic change. Perhaps it is this illusionary stasis that has deceived climate scientists who, believing they have found a rapid trend in planetary warming, have gone running to their governments and media outlets, warning of dire consequences ahead. The truth is, Earth’s climate has changed quite dramatically in the past, and often on short time scales. Just because modern day scientists have not personally observed such changes is irrelevant, nature is what it is.

During the Eemian interglacial, between 130,000-110,000 years ago, the Earth’s climate was generally much like that of today, though somewhat warmer and moister in many regions. According to climate proxy records derived from ice cores, extracted from the Greenland ice cap, the warm climate of the Eemian may have been punctuated by many sudden and fairly short-lived cold phases. Unfortunately, these results are somewhat inaccurate because the lower layers of the ice sheet have become jumbled and mixed up. However, at least one major cold and dry event during the Eemian seems to be corroborated by the terrestrial pollen record from Europe and China.

The timing of such events remains both vague and controversial in paleoclimate circles. Until a few decades ago it was generally thought that all large-scale global and regional climate changes occurred gradually over a timescale of many centuries or millennia, scarcely perceptible during a human lifetime. Still, many scientists have come to believe that there have been large changes in climate that have happened quickly enough to be noticed during a persons lifetime. Today, many climate change alarmists notice a change in a few tenths of a degree and call it “unprecedented” and “irreversible” when it is neither. A paper done by researchers at Oak Ridge National Laboratory’s Environmental Sciences Division outlines the evidence for the existence of rapid changes and possible causes for them. In “Sudden climate transitions during the Quaternary,” Jonathan Adams, Mark Maslin, and Ellen Thomas put it this way:

From present understanding of the record of the last 150,000 years, at least a few large climate changes certainly occurred on the timescale of individual human lifetimes, the most well-studied and well-established of these being the ending of the Younger Dryas, and various Holocene climate shifts. Many other substantial shifts in climate took at most a few centuries, and they too may have occurred over a few decades. The high time resolution in the climate record, however, is either not available, or records have not yet been studied in enough detail. Some very interesting new data sets may be expected to become available within a few years, as a result of drilling by the Ocean Drilling Program in the Saanich Inlet and in the northern Atlantic. It will take time before the meticulous work of logging year-by-year changes in long ice cores and lake records can give a relatively complete picture of when, and exactly how quickly, rapid climate changes occurred. There are many ‘suspected’ decade-timescale climate changes from the past (just as the Younger Dryas was until recently a ‘suspected’ but distinctly unproven decadal-scale climate shift), but very few ‘proven’ ones. Greater knowledge of how frequently such sudden events have occurred, and under what general circumstances, is required before a greater understanding can be reached.

The transition from interglacial to colder glacial conditions at the end of the Eemian is actively debated in climate circles—some say the transition was a slow slide into ever colder conditions, while others say it started with a quick cooling taking less than five hundred years. Regardless of how the last glacial period started, during the long glacial period conditions often changed in sudden leaps and bounds. Rapid temperature decline could be followed by several thousand years of relatively stable climate or even a temporary reversal to warmth. But inexorably, average global temperatures declined, particularly in the Northern Hemisphere. Boreal forest zones retreated and fragmented as the summers and winters grew colder. Large ice sheets began to grow in the northern latitudes when the snow that fell in winter failed to melt, and instead piled up from one year to the next until it reached thousands of meters in thickness.

Around 50,000 years ago, Creswell Crags near Sheffield was Europe’s northern frontier of settlement.

The point at which the global ice extent was at its greatest, about 21,000 years ago, is known as the last Glacial Maximum. The Glacial Maximum was much more arid than present almost everywhere, with desert and semi-desert occupying huge areas of the continents and forests retreated. But in fact, the greatest global aridity (rather than ice extent) may have been reached slightly after the Last Glacial Maximum, somewhere during the interval 19,000-17,000 years ago. This due to the lower sea levels uncovering large tracts of land that are underwater today.

Here is a summary of the sequence of events for the last 130,000 years, gleaned from the ORNL web site. Phases about as warm or warmer than the present are marked in bold.

  • – 150,000 y.a. – cold, dry full glacial world
  • – around 130,000 y.a. – rapid warming initiates the Eemian interglacial (Stage 5e)
  • – 130,000-110,000 y.a. – global climates generally warmer and moister than present, but with progressive cooling to temperatures more similar to present.
  • – (except for possible global cold, dry event at 121,000 y.a.)
  • – ?110,000 y.a. – a strong cooling marks the end of the Eemian interglacial (Stage 5e).
  • – 105,000-95,000 y.a. – climate warms slightly but still cooler and drier than present; strong fluctuations.
  • – 95,000 – 93,000 y.a. – another cooler phase similar to that at 110,000 y.a.
  • – 93,000 – 75,000 y.a. – a milder phase, resembling that at 105,000-95,000 y.a.
  • – 75,000 – 60,000 y.a. – full glacial world, cold and dry (the ‘Lower Pleniglacial’ or Stage 4)
  • – 60,000 – 25,000 y.a. – ‘middling phase’ of highly unstable but generally cooler and drier-than-present conditions (Stage 3)
  • – 25,000 – 15,000 y.a. – full glacial world, cold and dry; Stage 2 (includes the ‘Last Glacial Maximum’)
  • – (This period includes two ‘coldest phases’ – Heinrich Events – at around 23,000-21,000 y.a. and at 17,000-14,500 y.a.)
  • – 14,500 y.a. – rapid warming and moistening of climates in some areas. Rapid deglaciation begins.
  • – 13,500 y.a. – nearly all areas with climates at least as warm and moist as today’s
  • – 12,800 y.a. (+/- 200 years)- rapid onset of cool, dry Younger Dryas in many areas
  • – 11,500 y.a. (+/- 200 years) – Younger Dryas ends suddenly, back to warmth and moist climates (Holocene, or Stage 1)
  • – 9,000 y.a. – 8,200 y.a. – climates warmer and often moister than today’s
  • – about 8,200 y.a. – sudden cool and dry phase in many areas
  • – 8,000-4,500 y.a. – climates somewhat warmer and moister than today’s
  • – Since 4,500 y.a. – climates fairly similar to the present (except; about 2600 y.a. – relatively wet/cold event of unknown duration in many areas)

This is painting past climate in broad strokes—nature did not make such an orderly progression from one interglacial to then next. Sudden warm and moist phases occurred many times during the time span of the last glacial, often taking Greenland and Europe from a full-glacial climate to conditions about as warm as at present. For the time period between 115,000 and 14,000 years ago, twenty-five of these short lived warm events, called Dansgaard-Oeschger events, have so far been recognized from the Greenland ice core data, although many lesser warming events also occurred. These “interstadials” came on over the course of a few decades and lasted for varying spans of time, usually a few centuries to about 2,000 years. Then, equally rapid cooling returned conditions to their previous state.

The opposite of the interstadials were the Heinrich events. These sudden intense cold and dry phases occasionally affected the North Atlantic region and many other parts of the world. According to ORNL: “The Heinrich events were first recognized as the traces of ‘ice surges’ into the north Atlantic, but they show up in the Greenland ice cores and at least some are also detectable in the European pollen records and distant Antarctic ice cores. They may also show up as pine pollen peaks in Florida, and environmental changes in the Middle East, China, New Zealand and South America.”

So as we have seen, climate can vary wildly, particularly in the upper latitudes, swinging between warm and cold. Even during the depths of an “Ice Age” things were not uniformly frozen. In fact, most of the world was not covered with mile thick glaciers. And while forest areas were diminished and the overall climate less humid, there were still hot tropical areas and rainforests, as seen in the map below. Which means that our ancestors didn’t just huddle in caves eating mastodon steaks, some of them probably lived in much more temperate, even tropical regions, during the height of the last glacial.

Though this map shows the amazon as tropical grassland, recent research from the University of Michigan offers evidence of a different past. Radiocarbon dating and pollen analysis of sediments from a small lake in Brazil indicate that the western Amazon River basin remained covered with lush, tropical rain forest 14,000 to 30,000 years ago. Just more of that “settled science” I guess.

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