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The start of the glacial period was characterized by a mostly gradual cooling, lasting about five millennia1. The growth of ice sheets is necessarily a slow process, limited by the transfer of moisture through the atmosphere, and it appears likely that this process initially limited the rate of climatic cooling. Then, approximately 114,000 years ago, with temperatures having dropped less than halfway to typical full glacial values, the first rapid climate changes began — as documented here for the first time. The timing and characteristics of these events offer an invaluable subject for climate modellers; the mechanisms underlying rapid climate change are still being debated, and climate models have not yet convincingly predicted them.
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Cooling happened over 5000 years. A natural climatic cycle. The temperature increases we are experiencing now are too fast to be considered natural to any previous warming period.
And before you point out that this section states that the mechanisms are still up for debate on what causes rapid climate change, he is not stating whether it is human produced CO2 pollution. He is referring to climatic mechanisms or 'feedback' loops that the Earth engages at certain temperatures.
http://www.nature.com/nature/journal...l/431133a.html