sentences:  Bond events were previously believed to exhibit a roughly cycle, but the primary period of variability is now put at .Gerard C. Bond of the Lamont–Doherty Earth Observatory at Columbia University was the lead author of the 1997 paper that postulated the theory of 1470-year climate cycles in the Late Pleistocene and Holocene, mainly based on petrologic tracers of drift ice in the North Atlantic.However, more recent work has shown that these tracers provide little support for 1,500-year intervals of climate change, and the reported period was a statistical artifact.