(Click here for a full sized print (3000 pixels wide, suitable for printing).
...The upper part of the poster shows three ice core records. The top record is actually a composite reconstruction of six Greenland ice core records4. The middle chart is the most recent portion of the Vostok Antarctic ice core record, the entire Vostok 400,000 year record is show in the upper left of the poster....The bottom large chart is the actual temperature, calculated from a single central Greenland ice core.
Just below the Central Greenland ice core record the “Bond” cooling events over this 18,000 year period are noted7. The Bond cooling events average around 1,500 years apart and some are more dramatic than others. The 8.2, 5.9 and 4.2 kiloyear events were major events8,9, with dramatic cooling and they were huge disruptions for civilizations around the world. Others, like the 2.8 kiloyear event in the Iron Age were hardly noticed....
5.9 Kiloyear Bond Event
About 5,900 years ago the Sahara became a desert (The 5.9 kiloyear event or Bond event 4) and this very severe drought also ended the Ubaid empire and caused a huge migration of people from the Sahara region in search of food and water. The people migrated to river valleys, such as the Nile Valley in Egypt, in order to be close to water. Claussen, et al., 199936 has suggested that this drought was caused by a severe cooling event that occurred at the same time. The Sahara never recovers from this event. But, since the drought forces people into river valleys, larger cities are built and societies become more complex.
Following the end of the 5.9 kiloyear event and the end of the Holocene Thermal Optimum, around 4,500 years ago the earliest Egyptian pyramids are built, Stonehenge is constructed in present day England and the first large cities appear in India. The earliest Mayan cities appear a little over 600 years later around 3,900 years ago.
4.2 Kiloyear Bond Event
The 4.2 kiloyear event was a very cool period in the Arctic (the Bond Event 3) and it caused a very severe drought in the Middle East. This period caused a sudden collapse of the Egyptian government, famines and social disorder. Similar disruptions occurred in the Akkadian Empire, the Indus Valley and in China.
Around 3,300 years ago, the great Bronze Age civilizations in the Middle East collapsed. These included the Mycenaean’s, the Hittites and the Egyptian New Kingdom. This sudden collapse was probably caused by another extended and severe drought. The onset of this drought coincides with a sudden and extended cooling period in the Central Greenland ice core data. In general, most large scale droughts in the last 18,000 years appear to be associated with cooling in the Arctic. This marks the end of the Minoan Warm Period.