Anthropocene

Introduction

caption The Earth at night, demonstrating the global extent of human influence.

The Anthropocene defines Earth's most recent geologic time period as being human-influenced, or anthropogenic, based on overwhelming global evidence that atmospheric, geologic, hydrologic, biospheric and other earth system processes are now altered by humans. The word combines the root "anthropo", meaning "human" with the root "-cene", the standard suffix for "epoch" in geologic time. The Anthropocene is distinguished as a new period either after or within the Holocene, the current epoch, which began approximately 10,000 years ago (about 8000 BC) with the end of the last glacial period.

Origins of the term

Anthropocene is a new term, proposed in 2000 by Nobel Prize winning scientist Paul Crutzen. A similar term, Anthrocene, was coined by Andrew Revkin in his 1992 book Global Warming: Understanding the Forecast, but was not adopted by scientists. Crutzen noted that the term originated in 2000 at "a conference where someone said something about the Holocene. I suddenly thought this was wrong. The world has changed too much. So I said: 'No, we are in the Anthropocene.' I just made up the word on the spur of the moment. Everyone was shocked. But it seems to have stuck."[1]. Crutzen then proceeded to use the term in print in 2000[2]. In 2008, Zalasiewicz and colleagues published the first proposal for the formal adoption of the Anthropocene epoch by geologists, and this adoption is now pending [3].

Evidence for the Anthropocene

 

caption Figure 1: Increase in atmospheric carbon dioxide, 1744 to 2005. (Source: PhysicalGeography.net)

 

Geologic epochs are distinguished from one another based on geological observations, such as the composition of sediment layers and other tools of paleoclimatology. To justify the identification of a new Anthropocene epoch, it must therefore be demonstrated that evidence of anthropogenic global change is present at such a level that it can be distinguished using geologic indicators despite natural variability in these across the Holocene.

The most commonly cited and readily measured global change associated with humans is the rise of greenhouse gases, especially carbon dioxide and methane, around the beginning of the Industrial Revolution, together with the associated rise in global temperatures and sea level caused by this global warming. Other key indicators include massive global increases in soil erosion caused by land clearing and soil tillage for agriculture; massive deforestation; and massive extinctions of species caused by hunting and the widespread destruction of natural habitats.

When did the Anthropocene begin?

 

caption Human alteration of land surfaces.

 

The originator of the Anthropocene terminology, Paul Crutzen, favors the beginning of the Industrial Revolution as the starting point for the Anthropocene. In a 2002 paper in the journal Nature he stated: "The Anthropocene could be said to have started in the late eighteenth century, when analyses of air trapped in polar ice showed the beginning of growing global concentrations of carbon dioxide and methane."[4]. Zalasiewicz et al. are in general agreement with Crutzen that the Anthropocene is best identified at the beginning of the Industrial Revolution, though they also propose the beginning of the nuclear era in the 1960s as a useful date, due to the global presence of radioactive isotopes in sediments at this time.

However, as yet, there is no official start date for the Anthropocene. Moreover, William Ruddiman proposes that globally significant human alteration of greenhouse gas concentrations and associated climate change, extensive land clearing and soil erosion, and mass species extinctions actually began approximately 8,000 years ago with the rise of farming and the global spread of human populations in the latter stages of the first Agricultural Revolution. For this reason, the Anthropocene might be considered to begin 8,000 years ago. On the other hand, this "Early Anthropocene" definition is difficult to differentiate from the Holocene epoch which began only 2,000 to 4,000 years earlier.

See also

Notes

  1. ^ Fred Pearce, F. 2007. With Speed and Violence. Page 21. ISBN: 0807085774.
  2. ^ Crutzen, P. J., and E. F. Stoermer. 2000. The "Anthropocene". ''Global Change Newsletter''. 41: 17-18.
  3. ^ Zalasiewicz, J., M. Williams, A. Smith, T. L. Barry, A. L. Coe, P. R. Bown, P. Brenchley, D. Cantrill, A. Gale, P. Gibbard, F. J. Gregory, M. W. Hounslow, A. C. Kerr, P. Pearson, R. Knox, J. Powell, C. Waters, J. Marshall, M. Oates, P. Rawson, and P. Stone. 2008. Are we now living in the Anthropocene? GSA Today 18:4-8.
  4. ^ Crutzen, P. J. 2002. Geology of mankind. Nature 415:23-23.

Further Reading

  • Crutzen, P. J. 2002. Geology of mankind. Nature 415:23-23.
  • Ruddiman, W. F. 2003. The anthropogenic greenhouse era began thousands of years ago. Climatic Change 61:261-293.
  • Ruddiman, W. F. 2007. The early anthropogenic hypothesis: Challenges and responses. Reviews of Geophysics 45:RG4001.
  • Ruddiman, W. E. 2005. Plows, Plagues, and Petroleum: How Humans Took Control of Climate. Princeton University Press. ISBN: 0691133980.
  • De Vries, B. and J. Goudsblom. 2002. Mappae Mundi: Humans and their Habitats in a Long-term Socio-ecological Perspective: Myths, Maps and Models. Amsterdam University Press. ISBN: 9053566554.
  • Zalasiewicz, J., M. Williams, A. Smith, T. L. Barry, A. L. Coe, P. R. Bown, P. Brenchley, D. Cantrill, A. Gale, P. Gibbard, F. J. Gregory, M. W. Hounslow, A. C. Kerr, P. Pearson, R. Knox, J. Powell, C. Waters, J. Marshall, M. Oates, P. Rawson, and P. Stone. 2008. Are we now living in the Anthropocene? GSA Today 18:4-8.

External links

Glossary

Citation

Ellis, E. (2013). Anthropocene. Retrieved from http://www.eoearth.org/view/article/150125