Chapter 2 - Evidence for Synchronous Global Climatic Events: Cosmogenic Exposure Ages of Glaciations

Abstract

This chapter discusses the synchronous global climate events caused by the glaciations. Despite three decades of research on abrupt climate changes, such as the Younger Dryas (YD) event, the geological community is only now arriving at a consensus about its global extent, but has not established an unequivocal cause or a mechanism of global glacial response to rapid climate changes. At present, although Greenland ice cores have allowed the development of highly precise 18O curves, one cannot adequately explain the cause of abrupt onset and ending of global climatic reversals. In view of present global warming, understanding the cause of climate change is critically important to human populations—the initiation and cessation of the YD ice age were both completed within a human generation. The synchronous glacial fluctuations in the western United States, Europe, and New Zealand, i.e., in both hemispheres and on both sides of North America, suggest that several abrupt, global, simultaneous, climatic changes occurred during the late Pleistocene. Such changes cannot be explained by changes in the North Atlantic Deep Current alone because of the contemporaneity of glacial responses in both hemispheres with no time lag between hemispheres. The global sensitivity of the double YD suggests a common global cause, rather than an oceanic event that was propagated across the equator. Both 14C and 10Be production rates in the upper atmosphere changed during the YD, raising the possibility of changes in incoming radiation.