Thursday, February 18, 2010

Temperature and the Rise and Fall of Civilizations

Let me take you on a tour back in time.

These charts, except for the last one, are based on data from ice core samples in central Greenland, documented here:  Temperatures are in degrees C and represent average values.  Click on the charts for a larger version.

This is the temperature of central Greenland from 1400-1900.  There is a definite rise  that probably continues into the 20th century at least another 0.5 degree based on other data sources.  Wow.  Global Warming.

Now we go a little further back in time.  Note the Medieval Warm Period (MWP) around 1000 AD.  The Global Warming scientists find the MWP very inconvenient, and often simply remove it from their “homogenized” datasets.  This was when Greenland was settled by the Vikings.  Archeological evidence shows villages, agriculture, etc.  After all, they named it “Green Land”.   How did the polar bears survive?

This chart shows all of recorded history.  Note that ancient Egypt, Bronze-Age Greece, and the Roman Empire all correspond to warm times – much warmer than the present.  Look at how these milestones pretty much line up, with a little lag as civilizations sometimes coast on “warm momentum”:

    • 2600BC -- Egypt: Building of the Pyramids at Giza
    • 1200BC -- Mycenaean Greece: The Trojan War, Considered the high point of Bronze Age civilization
    • 1100BC-500BC -- Greece: Dark Age collapse
    • 500BC -- Greece: Beginning of Classic Age, Ended by the rise of Rome
    • 250BC-145BC -- Rome: Conquest of the Mediterranean
    • 96-180 -- Rome:  Pax Romana
    • 180 -- Rome: Decline begins after the death of Marcus Aurelius
    • 493 -- Rome: Italy absorbed by the barbarian Ostrogoths
    • 500-1000  -- Europe: Dark Ages or “Early Middle Ages”
    • 1000-1300 -- Europe: High Middle Ages,  Large population growth, arts and learning start up again
    • 1300-1500-- Europe: Late Middle Ages, The Renaissance
    • 1500-1820 -- Europe: Various Little Ice Ages, famine, black death, but also New World, Enlightenment etc. 
    • 1820-Present -- World: Rise of Industrial Civilization

Note that the overall  trend since the building of the pyramids is downward.  More on that later.

Now we go back to around 11,000 BC, and find that the beginnings of agriculture and civilization correspond to an amazing jump in temperature starting around 9,000 BC.  Our recent little “global warming” is starting to look infinitesimal.

Going back to 50,000 BC, we see an ice age ending in 9,000 BC, followed by warming and the rise of civilization.  That trough at 10,000 BC is called the Younger Dryas Stadial.  Astonishingly, the transition to colder temperatures during the Younger Dryas is believed to have occurred in as little as a decade (though I don’t see that in this Greenland dataset).

Going way back to earlier than 400,000 BC in the following chart, we see a series of ice ages, punctuated by short warm periods that pop up, often decline slowly, and then collapse.  Based on this, it appears that our particular 11,000 year warm spell is unusual, and likely to end soon.  This last chart is based on Antarctic “Vostok” ice cores

Summary: Civilization is dependent on, and is likely a direct result of a 11,000-year period of unusual global warmth.   Even minor temperature downturns within this warm period have been disastrous for civilizations prior to 1000 AD.  In the last 1000 years, modern civilizations have been able to survive minor cold periods, and even advance, but have done best in warm ones.  The observed secular downward temperature trend since the building of the Pyramids, combined with that fact that interglacial warm periods have not historically lasted much more than 10,000 years would indicate a high probability that the period of warmth that brought about the development of civilization and agriculture is ending and we are slowing entering the next ice age. The rapid onset of the Younger Dryas indicates that such a transition could occur in as little as 10 years – but of course it may not occur for another thousand years.

Modern world populations levels would be very difficult to support if the United States heartland, Canada, Russia, most of China, and northern Europe all became too cold for agriculture (as they usually have been over the last 400,000 years).  With the Livingston and Penn solar data (that I have mentioned before), I am somewhat concerned that we could see such an occurrence in our lifetimes, possibly by 2020.

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