IPCC report on climate variations, inter glacial temperatures and Ice ages.

Palaeoclimatic observations indicate that abrupt decadal to centennial-scale changes in the regional frequency of tropical cyclones, floods, decadal droughts and the intensity of the African-Asian summer monsoon very likely occurred during the past 10 kyr. However, the mechanisms behind these abrupt shifts are not well understood, nor have they been thoroughly investigated using current climate models.

IPCC Paleoclimate