I start the following series of posts (in this thread) by noting that I now concur with jai (see Reply #9) that it would be most rational to replace the Holocene Epoch with the name Anthropocene and that I also agree with Rubikscube (see Replies # 11 & 14) that the Anthropocene should be declared an Era instead of an Epoch. I will cite my reasons for supporting this definition of the Anthropocene Era (or Epoch) later, but first I would like to elaborate on some of the recent debate for other dates/definitions for the Anthropocene.
First, Wikipedia offers the following commentary regarding a definition for the Anthropocene: "In January 2015, 26 of the 38 members of the International Anthropocene Working Group published a paper suggesting that July 16, 1945 was the starting point of the proposed new epoch. However, a significant minority supports one of several alternative dates. In March 2015, another paper suggested either 1610 or 1964 could be the beginning of Anthropocene. The Anthropocene Working Group plans to meet in 2016 to submit evidence and decide whether the Anthropocene is a true geologic epoch."
I acknowledge that the "International Anthropogenic Working Group" will determine the formal definition of the Anthropocene Epoch (or Era) in 2016; and while further acknowledge that different scientific and socio-economic disciplines will likely have various definition of different relevant Ages/Periods/Eras (Neolithic Revolution, Age of Discovery, Industrial Revolution, Atomic Age, Information Age, etc. etc. etc.). Nevertheless, I plan to discuss the logic for simply, and entirely, re-defining the Holocene Epoch as the Anthropocene Era (or Epoch). By this line of logic (see Walker et al 2009, below), the Greenland NGRIP ice core would place the beginning of the Anthropocene Epoch at 9,700 BCE (or 11,700 years before the year 2000) +/- 99 years, and would continue until mankind stops having a dominant impact on the various Earth Systems.
Roughly speaking, I propose the line of logic that the Younger Dryas came to an unnaturally abrupt end associated with a marked change in atmospheric circulation regime (accompanied a temperature rise in Greenland of 10 +/4 C); which was triggered when the cumulative effect of the multi-millennial long anthropogenically induced Mega Fauna Extinction (here postulated to have reached a critical condition during the Younger Dryas when the last remaining Mega Fauna that where already stressed by anthropogenic impact, succumbed to cold snap) induced a tipping point in the atmospheric circulation pattern via changes in the biosphere (e.g. albedo changes as shrubs previously suppressed by high-latitude mega fauna grew above the on land snow cover, etc).
Walker, M.; Johnsen, S.; Rasmussen, S. O.; Popp, T.; Steffensen, J.-P.; Gibbard, P.; Hoek, W.; Lowe, J.; Andrews, J.; Bjo; Cwynar, L. C.; Hughen, K.; Kershaw, P.; Kromer, B.; Litt, T.; Lowe, D. J.; Nakagawa, T.; Newnham, R.; Schwander, J. (2009). "Formal definition and dating of the GSSP (Global Stratotype Section and Point) for the base of the Holocene using the Greenland NGRIP ice core, and selected auxiliary records" (PDF). J. Quaternary Sci. 24: 3–17. doi:10.1002/jqs.1227http://onlinelibrary.wiley.com/doi/10.1002/jqs.1227/abstract;jsessionid=4642F856F01B3EE7C526138127CEE75F.f01t01http://onlinelibrary.wiley.com/doi/10.1002/jqs.1227/epdf
Abstract: "The Greenland ice core from NorthGRIP (NGRIP) contains a proxy climate record across the Pleistocene–Holocene boundary of unprecedented clarity and resolution. Analysis of an array of physical and chemical parameters within the ice enables the base of the Holocene, as reflected in the first signs of climatic warming at the end of the Younger Dryas/Greenland Stadial 1 cold phase, to be located with a high degree of precision. This climatic event is most clearly reflected in an abrupt shift in deuterium excess values, accompanied by more gradual changes in δ18O, dust concentration, a range of chemical species, and annual layer thickness. A timescale based on multi-parameter annual layer counting provides an age of 11 700 calendar yr b2 k (before AD 2000) for the base of the Holocene, with a maximum counting error of 99 yr. A proposal that an archived core from this unique sequence should constitute the Global Stratotype Section and Point (GSSP) for the base of the Holocene Series/Epoch (Quaternary System/Period) has been ratified by the International Union of Geological Sciences. Five auxiliary stratotypes for the Pleistocene–Holocene boundary have also been recognised."
Extract: "These various data sources reﬂect a marked change in atmospheric circulation regime accompanied by a temperature rise, probably of the order of 10 +/-4oC, at the onset of the Holocene …"
Making a distinction between the Holocene Extinction and the Anthropocene seems to me that it would be short sighted (on the part of the International Anthropocene Working Group) as the Holocene Extinction is clearly related to human activities as it’s either eight to 100 times up to about 100 to 1,000 times the normal rate of extinction among species.
I conclude this post with a few Wikipedia links & abstracts regarding: (a) The Sixth Extinction; (b) The Holocene Extinction; and (c) the most recent series of megafaunal extinction pulses.http://en.wikipedia.org/wiki/The_Sixth_Extinction_(book)
Extract: "The Sixth Extinction: An Unnatural History is a 2014 nonfiction book written by Elizabeth Kolbert and published by Henry Holt & Company. The book covers past mass extinctions and demonstrates that the earth and humans are in the midst of a "sixth" mass extinction. She chronicles previous mass species extinction events, as well as specific species extinguished by humans thousands of years ago, such as the great auk; and she includes the accelerated widespread extinction of many species during our present time. Kolbert also describes prehistoric and historic ecologies surrounding prior and near-present species extinguishing events. The author received the Pulitzer Prize for General Non-Fiction for the book in 2015.
Human behavior disrupts earth's balanced and interconnected systems "putting our own survival in danger." Consequently, the earth systems currently affected are: the global atmosphere, the water cycle, the ocean's thermal or heat absorption, ocean acidity and coral reefs, soil moisture and drought conditions, plant destruction by pests or non-indigenous fauna or heat stress, heat regulation by the earth's ice, and so on.
The human species contributes to this disruption - even without intending to - because of our innate capabilities to alter the planet at this stage of our cultural evolution; for instance, we now have the ability to harness energy from beneath the earth's surface. Homo sapiens also has the ability to adapt relatively quickly to almost any environment on this planet's surface. Other species, however, have a hard time relocating to new, suitable habitats. They are unable to migrate ahead of current rapid ecological changes, or are hampered by artificial barriers such as roadways, cityscapes, and suburban sprawl, which cause increased discontinuity between viable habitats throughout world.
Kolbert states that human activity has transformed between a third and a half of land surface on the planet. We have damned most of the major rivers of world, increased levels of nitrogen than can be fixed naturally by terrestrial ecosystem, used more than half of the world’s readily accessible freshwater run-off, removed more than one third of the primary producers of the oceans’ coastal waters, and changed the composition of the atmosphere by deforestation and fossil fuel combustion."http://en.wikipedia.org/wiki/Holocene_extinction
Extract: "The Holocene extinction, sometimes called the Sixth Extinction, is a name proposed to describe the currently ongoing extinction event of species during the present Holocene epoch (since around 10,000 BCE) mainly due to human activity."http://en.wikipedia.org/wiki/Megafauna
Extract: "However, this extinction pulse near the end of the Pleistocene was just one of a series of megafaunal extinction pulses that have occurred during the last 50,000 years over much of the Earth's surface, with Africa and southern Asia (where the local megafauna had a chance to evolve alongside modern humans) being largely spared. The latter areas did suffer a gradual attrition of megafauna, particularly of the slower-moving species (a class of vulnerable megafauna epitomized by giant tortoises), over the last several million years.
Outside the mainland of Afro-Eurasia, these megafaunal extinctions followed a highly distinctive landmass-by-landmass pattern that closely parallels the spread of humans into previously uninhabited regions of the world, and which shows no correlation with climatic history (which can be visualized with plots over recent geological time periods of climate markers such as marine oxygen isotopes or atmospheric carbon dioxide levels). Australia was struck first around 45,000 years ago, followed by Tasmania about 41,000 years ago (after formation of a land bridge to Australia about 43,000 years ago), Japan apparently about 30,000 years ago, North America 13,000 years ago, South America about 500 years later, Cyprus 10,000 years ago, the Antilles 6000 years ago, New Caledonia and nearby islands 3000 years ago, Madagascar 2000 years ago, New Zealand 700 years ago, the Mascarenes 400 years ago, and the Commander Islands 250 years ago."
(also see that attached image from this reference showing a timeline of human migration; which correlates tightly with the timeline of megafauna extinction)
Again, my definition of the beginning of the Anthropocene is the point when human control of tools cause the global Earth Systems to be changed beyond natural variation. This first requires human (homo sapiens sapiens) population to be reasonably dispersed around the world (i.e. South America was populated by 10 kya); and second to have unbalanced some key Earth Systems (i.e. megafaunal extinctions & associated changes in the megafaunal habits due to their loss, which for practical purposes occurred 10 kya in South America). Thus it is my recommendation that the entire Holocene be renamed as the Anthropocene, as it is during this period that the Holocene Extinction/Sixth Extinction has been accelerating.