Reuters: Abrupt shifts in the climate such as the end of Ice Ages could provide an early warning system for modern changes such as prolonged droughts, a leading scientist said on Monday. The sudden desertification of North Africa 5,500 years ago or a warming at the end of the last Ice Age 11,000 years ago were preceded by signs of a less stable climate, according to Marten Scheffer of Wageningen University in the Netherlands. That insight, reported last year, is now being applied to try …