These charts, except for the last one, are based on data from ice core samples in central Greenland, documented here: http://www.ncdc.noaa.gov/paleo/metadata/noaa-icecore-2475.html. Temperatures are in degrees C and represent average values. Click on the charts for a larger version.
- 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.
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.