The Anthropocene, the geological epoch when humans have had an overriding influence on the earth and its atmosphere, is a step closer to being formally recognised as a geological period – and apparently it all started in 1610!
(image from http://mariepelin.m143.net)
The term ‘The Anthropocene’ was first coined in 2000 by Eugene Stoermer and made popular by the atmospheric chemist and Nobel Laureate Paul Crutzen. This geological epoch, which follows the Holocene, is defined as the period when humans have had an overriding influence on the earth and its atmosphere. The word is derived from the Greek roots for anthropo- meaning “human” and -cene meaning “new.” (see previous post on the Anthropocene)
Whilst most agree that humans have caused some fundamental changes in the earth and its atmosphere, and enough to be recognised as a new epoch, the exact start of the period has so far not been formally agreed. Recent work published in Nature this week, pushes for the Anthropocene to be recognised from 1610. However not all geologists agree, and the timing of the start of the Anthropocene is causing surprisingly intense debate, with others pushing for the start of the period to coincide with the beginnings of large scale agriculture (5000 years ago), a surge in mining (3000 years ago), the start of the industrial revolution (mid 1800s) or the first atomic bomb testing (mid 1900s).
For geological periods to be recognised, there needs to be a recognisable signal in rock deposits (and these are usually defined by changes in fossil profiles) that characterises the time boundary. The major extinctions during the earths past have been the recognisable boundaries between some of the major geological time periods (Cambrian, Permian, Cretaceous, Tertiary). The Holocene is the most recently recognised geological period (defined in 2008), and refers to the warm period since the last ice age. This period is formally recognised as starting 11,700 years before present, and because the period is too recent to have fossil deposits associated with it, it is defined by the chemical signature of global climatic warming in an ice core from Greenland (at a depth of 1,492.45 m to be precise).
The new work on the Anthropocene pushes for the start of this new period to be recognised as a noticeable drop in atmospheric CO2 concentrations between 1570 and 1620, and which is clearly observable in multiple ice cores. This atmospheric climatic signal has been linked to the deaths of over 50 million indigenous people in the New World (the Americas), triggered by the arrival of Europeans. With the drop in global CO2 concentrations linked to the ensuing natural reforestation of over 65 million hectares of abandoned agricultural fields.
The proposal is currently being evaluated by the Anthropocene Working Group of the International Commission on Stratigraphy (ICS). This group will deliver its verdict soon on when whether and when the Anthropocene will be recognised.
The debate has also highlighted the multiple and intense impacts humans have had on the earth over the last 5000 years. The key decision now is which human-induced global disaster milestone we wish to recognise as the start of this period!
Links and references
Crutzen, P. J., and E. F. Stoermer (2000). “The ‘Anthropocene’”. Global Change Newsletter 41: 17–18.
Jones N (2011) Human influence comes of age: Geologists debate epoch to mark effects of Homo sapiens. Nature 473, 133 (11 May 2011) doi:10.1038/473133a. Also see Comment: The human epoch (2011)Nature 473, 254 (19 May 2011) doi:10.1038/473254a
Lewis SL, Maslin MA (2015) Defining the Anthropocene. Nature: Perspectives 519, 171–180 (12 March 2015) doi:10.1038/nature14258
Monastersky R (2015) The human age: Nature News and Comment. Nature 519, 144–147 (12 March 2015) doi:10.1038/519144a
Journal of Quaternary Science. 24, 3–17 (2009).et al. (2009)