Ruddiman et al think the anthropocene is a useful, necessary concept, but one which ought to remain someone nebulous, but the start ought to be 1945 (first atom bomb blast):
Defining the epoch we live in
Authors:
Ruddiman et al
Abstract:
Human alterations of Earth's environments are pervasive. Visible changes include the built environment, conversion of forests and grasslands to agriculture, algal blooms, smog, and the siltation of dams and estuaries. Less obvious transformations include increases in ozone, carbon dioxide (CO2), and methane (CH4) in the atmosphere, and ocean acidification. Motivated by the pervasiveness of these alterations, Crutzen and Stoermer argued in 2000 that we live in the “Anthropocene,” a time in which humans have replaced nature as the dominant environmental force on Earth (1). Many of these wide-ranging changes first emerged during the past 200 years and accelerated rapidly in the 20th century (2). Yet, a focus on the most recent changes risks overlooking pervasive human transformations of Earth's surface for thousands of years, with profound effects on the atmosphere, climate, and biodiversity.
OTOH, Lewis and crew think definitions are really important for science and if we're going to use the term 'anthropocene' we ought to it down to a formal start geologically & according to the GSSP standards:
Definitions are one of the bedrocks of science. However, W. F. Ruddiman et al. (“Defining the epoch we live in,” Perspectives, 3 April, p. 38) propose that the geological term Anthropocene should remain deliberately undefined and ambiguous. They recommend not formalizing the term because some inception dates miss important earlier human-induced environmental impacts, particularly widespread farming. We have sympathy for this view. However, defining the Anthropocene as a geological epoch must be based on evidence, including changes to the Earth system lasting millions of years and the existence of stratigraphic evidence marking such changes (1). All other geological time-units have agreed-upon dated markers or agreed-upon dates. The Anthropocene should not be treated differently.
link.
Certini et al agree with Lewis and crew about needing to make the anthropocene into something formal, but they suggest the anthropocene subsueme the holocene:
In their Perspective “Defining the epoch we live in” (3 April, p. 38), W. F. Ruddiman et al. write that in spite of its popularity, the Anthropocene still lacks an official onset. They propose that the term anthropocene be used informally (without the initial capital), which would avoid the constraints of a formal designation. We disagree.
[...]
Even if the impact of humans was not immediately major and uniform across the planet, what are a few thousand years of discrepancy between the end of the last glacial period and the dawn of the Anthropocene in comparison to the entire geological scale? Most transitions between the formally defined epochs would be much longer than the Holocene. Anthropocene seems a more reasonable name than Holocene for this combined time span, whose most characteristic trait is the human pressure on the planet. Holocene could possibly be the first stage of the Anthropocene, the one characterized by a soft and spotty human impact on Earth.
link.
Ruddiman counters the formalism is 'silly,' but does point out if the anthropocene is going to go formal, when to date it. The atom bomb or the start of the megafauna overkills?
Certini and scalenghe and Lewis and Maslin seem convinced that geoscience must rely heavily on formal stratigraphic nomenclature to move forward. This view likely originates from the centuries-long effort to compile the relative geologic age sequence, which was a monumental achievement, especially given religious and social opposition. The compilation required careful attention to stratigraphic principles such as superposition, index fossils, diachroneity, and facies changes. Over time, the findings became formalized in geologic nomenclature.
link.
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