About 2.6 million years ago at the start of Pleistocene epoch, large ice sheets up to several kilometres thick began to appear in the northern hemisphere. These ice sheets would advance during cooler glacial periods and retreat during warmer interglacials.
We are living during an interglacial period called the Holocene that started about 11,500 years ago.
Ice ages are powerful evidence of the natural climate change that has occurred on the Earth in the geological past. In the 21st century the effect that humans are having on this natural cycle is an area of active scientific investigation.
Image: Artist's impression of a herd of woolly mammoths, creatures that lived during the last glacial period and went extinct about 10,000 years ago (credit: Christian Darkin/SPL)
We are living in an age of ice.
Dr Iain Stewart explains that we are living during a relatively warm period of an ice age.
Anna Grayson follows a trail of geological clues.
Anna Grayson follows a trail of geological clues to find out how modern day England was separated from what is now France hundreds of thousands of years ago during an ice age. She speaks to geologist Phil Gibbard who helps her understand the region's geological history.
Iain Stewart explains how the rise of farming may have prevented an ice age.
Professor Iain Stewart describes a new theory that the rise of farming about 11,000 years ago released enough greenhouse gases into the atmosphere to prevent the onset of another ice age.
Quaternary glaciation, also known as the Pleistocene glaciation or the current ice age, refers to a series of glacial events separated by interglacial events during the Quaternary period from 2.58 Ma (million years ago) to present. During this period, ice sheets expanded, notably from out of Antarctica and Greenland, and fluctuating ice sheets occurred elsewhere (for example, the Laurentide ice sheet). The major effects of the ice age are erosion and deposition of material over large parts of the continents, modification of river systems, creation of millions of lakes, changes in sea level, development of pluvial lakes far from the ice margins, isostatic adjustment of the crust, and abnormal winds. It affects oceans, flooding, and biological communities. The ice sheets themselves, by raising the albedo, effect a major feedback on climate cooling.