Asked by Ian Sanders
There has been a series of ice ages over the past million years or so. Sometimes this whole period is referred to as the ‘ice age’, although it has included many individual glacial periods that alternated, every hundred thousand years or so, with warm periods called interglacials. More accurately, the ‘last ice age’ refers to the most recent of these glacial episodes. This global descent into cold climate started about 100,000 years ago and ended 11,700 years ago. That whole period can be regarded as the last ice age, though it was also complex, with varying climate.
The coldest part, when massive glaciers extended as far south as Britain, happened between 25,000 and 20,000 years ago; we call it the last glacial maximum. When will the next ice age be? Past interglacials have been quite variable in length; ours so far has lasted 11,700 years. According to geophysicists, our interglacial still has several thousand years left to run, after which another ice age may well begin. However, human inﬂuence could change everything. The climate system is very complex and delicate, and global warming could hugely affect the onset of the next ice age.
Adrian Lister, Palaeontology, NHM London