The realization that we are living in an ice age is relatively new and did not come easily. In 1830 Louis Agassiz, a young Swiss geologist, resigned himself to the evidence he had seen with his own eyes that an icecap once covered the Swiss Alps, but it took him many years to convince others of the reality of an ice age. To us this seems odd, because the traces of the former icecaps of North America and Europe are so conspicuous. The walls of debris left where ice fronts once melted eloquently testify to processes that no longer shape the temperate zones. Once the concept of so large a climate change had been accepted, however, it proved fertile and occupies the minds of climatologists and geologists to this very day.

Progress in understanding the Quaternary ice age has not been swift. Until the early 1970s almost everyone believed that four or at most five glacial periods, separated by interglacials, adequately described the history of the ice age. This has turned out to be a major error that resulted mainly from a lack of appreciation of the damage done by successive ice advances to the record left by their predecessors. Only when a far more complete Quaternary record was found in the sediments of the deep ocean, did the truth emerge.