Holocene Epoch

↑ Pleistocene
Holocene
Preboreal (10.3 ka – 9 ka), Boreal (9 ka – 7.5 ka), Atlantic (7.5 ka – 5 ka), Subboreal (5 ka – 2.5 ka) Subatlantic (2.5 ka – present)

The term Anthropocene is used by some scientists to describe the most recent period in the Earth's history. It has no precise start date, but may be considered to start in the late 18th century when the activities of humans first began to have a significant global impact on the Earth's climate and ecosystems. This date coincides with the 1775 commercialization of the Watt steam engine.[1] Other commentators link it to earlier events, such as the rise of agriculture. The term was coined in 2000 by the Nobel Prize-winning atmospheric chemist Paul Crutzen, who regards the influence of human behavior on the Earth in recent centuries as so significant as to constitute a new geological era. Use of this concept as an official geological concept gained support in early 2008, with publication of two new papers supporting this idea.[2]

Etymology

Anthropocene was coined in 2000 by the Nobel Prize-winning scientist Paul Crutzen by analogy with the word "Holocene." The Greek roots are anthropo- meaning "human" and -cene meaning "new." Crutzen has explained, "I was 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."[3] Crutzen first used it in print in a 2000 newsletter of the International Geosphere-Biosphere Programme (IGBP), No.41. In 2008, Zalasiewicz suggested in GSA Today that an anthropocene epoch is now appropriate.[2]

A similar term, Homogenocene (from old Greek: homo-, same geno-, kind, kainos-, new and -cene, period) was first used by Michael Samways in his editorial article in the Journal of Insect Conservation (1999) titled, "Translocating fauna to foreign lands: here comes the Homogenocene".[4] Samways used the term to define our current geological epoch, in which biodiversity is diminishing and ecosystems around the globe become more similar one to another. The term was used by John L. Curnutt in 2000 in Ecology, in a short list titled "A Guide to the Homogenocene."[5] Curnutt was reviewing Alien species in North America and Hawaii: impacts on natural ecosystems by George Cox.

Andrew Revkin coined the term Anthrocene in his book Global Warming: Understanding the Forecast (1992), in which he wrote, "we are entering an age that might someday be referred to as, say, the Anthrocene. After all, it is a geological age of our own making." The word Anthropocene is generally regarded as being a more suitable technical term.[6]

Definition of era

While much of the environmental change occurring on Earth is a direct consequence of the industrial revolution, William Ruddiman has argued that the Anthropocene began approximately 8,000 years ago with the growth of farming. At this point, humans were dispersed across all of the continents (bar Antarctica), and the Neolithic Revolution was ongoing. During this period, humans developed agriculture and animal husbandry to supplement or replace hunter-gatherer subsistence. Such innovations were followed by a wave of extinctions, beginning with large mammals and land birds. This wave was driven by both the direct activity of humans (e.g. hunting) and the indirect consequences of land-use change for agriculture.

This period (10,000 years to present) is usually referred to as the Holocene by geologists. For the majority of the Holocene, human populations were relatively low and their activities considerably muted relative to that of the last few centuries. Nonetheless, many of the processes currently altering the Earth's environment were already occurring during this period.

Nature of human effects

One obvious geological signal of human activity is increasing atmospheric carbon dioxide (CO₂) content. During the glacial-interglacial cycles of the past million years, natural processes have varied CO₂ by approximately 100 ppm (from 180 ppm to 280 ppm). As of 2006, anthropogenic net emissions of CO₂ have increased its atmospheric concentration by a comparable amount from 280 ppm (Holocene or pre-industrial "equilibrium") to more than 383 ppm. This signal in the Earth's climate system is especially significant because it is occurring much faster, and to an enormously greater extent, than previous, similar changes. Most of this increase is due to the combustion of fossil fuels such as coal, oil and gas, although smaller fractions are the result of cement production and land-use changes (e.g. deforestation).

Early anthropocene

Arguing the early Anthropocene hypothesis, William Ruddiman claims that the Anthropocene, as defined by significant human impact on greenhouse gas emissions, began not in the industrial era, but 8,000 years ago, as ancient farmers cleared forests to grow crops.[7][8][9] Ruddiman's work has in turn been challenged on the grounds that comparison with an earlier interglaciation ("Stage 11", around 400,000 years ago) suggest that 16,000 more years must elapse before the current Holocene interglaciation comes to an end, and that thus the early anthropogenic hypothesis is invalid.^{[citation needed]} But Ruddiman argues that this results from an invalid alignment of recent insolation maxima with insolation minima from the past, among other irregularities which invalidate the criticism.

See also

• Anthropocentrism
• Anthropogenic biomes
• Holocene extinction

References

Further reading

• Schmidt, G. A., D. T. Shindel and S. Harder, "A note on the relationship between ice core methane concentrations and insolation", Geophysical Research Letters, Vol. 31, Issue 23, CiteID L23206, 16 December 2004.
• Ruddiman, William F., "The anthropogenic greenhouse era began thousands of years ago", Climatic Change, No. 61 (3). pp. 261–293, Dec 2003.
• Ruddiman, William F., Stephen J. Vavrus and John E. Kutzbach, "A test of the overdue-glaciation hypothesis", Quaternary Science Reviews 24, p. 11, 2005.
• Ruddiman, William F., Plows, Plagues, and Petroleum: How Humans Took Control of Climate, Princeton University Press, 2005.

External links

• Interview with Paul Crutzen, New Scientist
• copy of IGBP article on Crutzen's website
• New Scientist blog entry on the formalisation of the term 'Anthropocene'
• "The Starving Oceans", Fishery Crisis
• Videos of a Radcliffe conference on Biodiversity in the Anthropocene, March 10, 2006
• Debate over the Early Anthropogenic Hypothesis
• "Human-Driven Planet: Time to Make It Official?", Science
• "Earth Is Us", Dot Earth blog, New York Times, January 28, 2008
• "Anthropocene", Encyclopedia of Earth
• Recent work on the Early Anthropocene Hypothesis presented at AGU
• (French) Thierry Picquet, "New era in the evolution of the world", Planétarisation