<Tr> <Td> Mean atmospheric CO 2 content over period duration </Td> <Td> c. 250 ppm (1 times pre-industrial level) </Td> </Tr> <Tr> <Td> Mean surface temperature over period duration </Td> <Td> c. 14 ° C (0 ° C above modern level) <P> </P> </Td> </Tr> <P> Quaternary (/ kwəˈtɜːrnəri /) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.588 ± 0.005 million years ago to the present . The Quaternary Period is divided into two epochs: the Pleistocene (2.588 million years ago to 11.7 thousand years ago) and the Holocene (11.7 thousand years ago to today). The informal term "Late Quaternary" refers to the past 0.5--1.0 million years . </P> <P> The Quaternary Period is typically defined by the cyclic growth and decay of continental ice sheets associated with Milankovitch cycles and the associated climate and environmental changes that occurred . </P>

When did the quaternary period begin and end