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1
Article
by Martin J. Head
1
*, Will Steffen
2
, David Fagerlind
3
, Colin N. Waters
4
, Clement Poirier
5
,
Jaia Syvitski
6
, Jan A. Zalasiewicz
4
, Anthony D. Barnosky
7
, Alejandro Cearreta
8
,
Catherine Jeandel
9
, Reinhold Leinfelder
10
, J.R. McNeill
11
, Neil L. Rose
12
,
Colin Summerhayes
13
, Michael Wagreich
14
, and Jens Zinke
4
The Great Acceleration is real and provides a quantitative basis
for the proposed Anthropocene Series/Epoch
Department of Earth Sciences, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, Ontario L2S 3A1, Canada;
*Corresponding author, E-mail: mjhead@brocku.ca
Fenner School of Environment and Society, Australian National University, Canberra, ACT 0200, Australia
Stockholm Resilience Centre, Stockholm University, Kräftriket 2B, SE-10691, Sweden
School of Geography, Geology and the Environment, University of Leicester, University Road, Leicester LE1 7RH, UK
Normandie Université, UNICAEN, UNIROUEN, CNRS, M2C, 14000 Caen, France
INSTAAR, University of Colorado, Boulder, CO 80309, USA
Jasper Ridge Biological Preserve, Stanford University, Stanford, CA 94305, USA
Departamento de Geología, Facultad de Ciencia y Tecnología, Universidad del País Vasco UPV/EHU, Apartado 644, 48080 Bilbao, Spain
LEGOS, Université de Toulouse, CNES, CNRS, IRD, UPS, 14 avenue Édouard Belin, 31400 Toulouse, France
Department of Geological Sciences, Freie Universität Berlin, Malteserstr. 74-100/D, 12249 Berlin, Germany
Georgetown University, Washington DC, USA
Environmental Change Research Centre, Department of Geography, University College London, Gower Street, London WC1E 6BT, UK
Scott Polar Research Institute, University of Cambridge, Lensfield Road, Cambridge CB2 1ER, UK
Department of Geodynamics and Sedimentology, University of Vienna, A-1090 Vienna, Austria
(Received: April 7, 2021; Revised accepted: October 7, 2021)
https://doi.org/10.18814/epiiugs/2021/021031
The Anthropocene was conceptualized in 2000 to reflect
the extensive impact of human activities on our planet,
and subsequent detailed analyses have revealed a sub-
stantial Earth System response to these impacts begin-
ning in the mid-20
th
century. Key to this understanding was
the discovery of a sharp upturn in a multitude of global
socio-economic indicators and Earth System trends at
that time; a phenomenon termed the ‘Great Acceleration’. It
coincides with massive increases in global human-con-
sumed energy and shows the Earth System now on a tra-
jectory far exceeding the earlier variability of the Holocene
Epoch, and in some respects the entire Quaternary Period.
The evaluation of geological signals similarly shows the
mid-20
th
century as representing the most appropriate incep-
tion for the Anthropocene. A recent mathematical analysis has
nonetheless challenged the significance of the original Great
Acceleration data. We examine this analytical approach and
reiterate the robustness of the original data in supporting
the Great Acceleration, while emphasizing that intervals
of rapid growth are inevitably time-limited, as recognised
at the outset. Moreover, the exceptional magnitude of this
growth remains undeniable, reaffirming the centrality of
the Great Acceleration in justifying a formal chronos-
tratigraphic Anthropocene at the rank of series/epoch.
Introduction
The Anthropocene was proposed in 2000 from the perspective of
Earth System science to reflect the profound impact of human activi-
ties on our planet, with a suggested onset in the latter part of the 18
century (Crutzen and Stoermer, 2000; Crutzen, 2002). The term had
in fact been used informally, and for a limited time, by biologist
Eugene Stoermer in the 1980s. Stoermer had not been interested in
pursuing its further use and was clear that Crutzen should be rec-
ognised as the sole originator of the term Anthropocene and its con-
cept as we essentially use it today.
Pfister (1992, 1994) had already drawn attention to socio-eco-
nomic shifts in the mid-20 century that he labelled ‘the 1950s syn-
drome’ – but with regard to Europe rather than the planet as a whole.
In 2004, an interval around the year 1950 was discovered within the
Earth System science community to represent the most pronounced
upward deflections of numerous global socio-economic indicators
and Earth System trends, including those that can be recognized in
geological strata (Steffen et al., 2004). The deflection became known
as the ‘Great Acceleration’ (Steffen et al., 2007) echoing Karl Polanyi’s
1944 holistic societal analysis The Great Transformation. The Great
Acceleration expressed a similarly holistic, comprehensive and inter-
linked depiction of post-1950 changes covering socio-economic fac-
tors and biophysical processes as well as environmental and climatic
personal reprint, published online first, 15 Nov 2021
2
changes (Steffen et al., 2015). It represents both a range of over-
whelming human impacts from the mid-20 century onwards and the
Earth System responses to them. The Great Acceleration dataset and
its analysis, having been published by Steffen et al. (2004, 2007), was
then extended by Steffen et al. (2015; see also Broadgate et al., 2014
for the online dataset).
Human global energy consumption, economic productivity, and
population growth have recently been analysed for the past 12,000
years (Syvitski et al., 2020). All were found to be highly correlated
and show significant increases in growth along with other key envi-
ronmental indicators at around 1950 CE (Fig. 2). In particular, anthro-
pogenic CO emission rates, upstream sequestration of sediment, the
number of synthetic mineral-like compounds, concrete and plastics
production, rates of population decline within species and transloca-
tion of species, declines in river runoff, accelerated sea-level rise, and
increased coastal hypoxia all show order-of-magnitude increases after
~1950 CE (Syvitski et al., 2020). These analyses independently sup-
port the critical role of the Great Acceleration in conceptualizing the
Anthropocene. The Great Acceleration represents a significant upward
deflection in the Earth System trajectory, causing an abrupt departure
from the envelope of variability that characterises the Holocene from
its inception 11,700 years b2k through to the mid-20 century.
Against this significant body of analysis, Nielsen (2018a, b, and
2021a) mathematically analysed the Great Acceleration dataset of
Steffen et al. (2015; also Broadgate et al., 2014) and combined these
data with an earlier analysis (Nielsen, 2017) of human population and
economic growth. Nielsen asserted that the growth rates of most of the
datasets fit hyperbolic trajectories up to around 1960 or later, at which
point they depart from that historical trend into periods of decreasing
growth rates, leading to his introduction of the term ‘Great Decelera-
tion’. He concluded that the Great Acceleration data cannot be used to
support a beginning for the Anthropocene, and indeed with no sud-
den intensification of growth there is no evidence to justify a new geo-
logical epoch (Nielsen, 2021a). Nielsen (2021b) drew a similar conclusion
from his analysis of the data provided in Syvitski et al. (2020).
The purpose of this article is to place the Great Acceleration in its
historical and present context, to clarify and reaffirm the significance
of the Great Acceleration for the Anthropocene both in terms of tim-
ing of inception and magnitude of growth, and to correct fundamental
misrepresentations (Nielsen, 2018a, b, and 2021a, b). Finally, we
emphasize the geological significance of the Great Acceleration and
summarize the case for a formal chronostratigraphic Anthropocene at
the rank of series/epoch.
The Great Acceleration
What came to be known as the Great Acceleration graphs origi-
nated in the IGBP (International Geosphere-Biosphere Programme)
synthesis project, led by one of us (WS). They were first published in
the 2004 book Global Change and the Earth System: A Planet Under
Pressure (Figs. 3.66 and 3.67 in Steffen et al., 2004). The graphs show
(i) the very large increases in magnitude of the human drivers of global
change, with the most rapid changes occurring from around 1950
onwards, and (ii) their impacts on the structure and functioning of the
Earth System, leading many environmental signals to show pronounced
changes following the mid-20 century. They play a central role as the
fundamental Earth System evidence for a steep trajectory of the sys-
tem away from Holocene conditions beginning around the mid-20
century.
The term ‘Great Acceleration’ was first coined in a Dahlem Work-
shop, held in Berlin, Germany, 12–17 June, 2005, a year after the
graphs were published in the IGBP synthesis volume. It was the 96
workshop in the Dahlem series and had the title Integrated History
and future Of People on Earth (IHOPE). The term emerged during a
wide-ranging discussion of human-driven changes to the global envi-
ronment through the 20 century, the magnitude and rate of these
changes, and their underlying potential human driving forces, among
a mixed group of social scientists, natural scientists and humanities
scholars convened and chaired by W. Steffen (Hibbard et al., 2007).
Quaternary
Holocene
Pleistocene
Calabrian
Gelasian
11,700 yr b2k
~129 ka
0.774 Ma
1.80 Ma
2.58 Ma
present
System /
Period
Upper / Late
Middle
Lower / Early
Series /
Epoch
Subseries /
Stage / Age
GSSP
Upper / Late
Middle
Lower / Early
Subepoch
8236 yr b2k
4250 yr b2k
Meghalayan
Northgrippian
Greenlandian
Anthropocene
mid-20th
Phanerozoic (pars)
Cenozoic (pars)
Quaternary
Holocene
Pleistocene Chibanian
Calabrian
Gelasian
11,700 yr b2k
~129 ka
0.774 Ma
1.80 Ma
2.58 Ma
present
Eonothem / Eon
Erathem / Era
System / Period
Upper / Late
Middle
Lower / Early
Series / Epoch
Subseries /
Stage / Age
GSSP
Upper / Late
Middle
Lower / Early
Stage 4
Subepoch
8236 yr b2k
4250 yr b2k
Meghalayan
Northgrippian
Greenlandian
a) Present ratified scheme b) Anthropocene added
century
Chibanian
Stage 4
Stage 8
Figure 1. Formal chronostratigraphic subdivision of the Quaternary System/Period showing: a) the present IUGS-ratified scheme (Head et
al., 2021), and b) the Anthropocene included according to the current preferences of the Anthropocene Working Group. Black type and yel-
low golden-spike symbols indicate ratified names and Global boundary Stratotype Sections and Points (GSSPs); grey type and grey golden-
spike symbols indicate names not yet approved (Stage 4 and Stage 8 are placeholders) and GSSPs in progress. The abbreviation yr b2k = years
before 2000 CE.
3
The parallel between, on the one hand, the interlocked set of transi-
tions in the 18 and 19 centuries among methods of economic pro-
duction, social behavior, politics and law observed by Polanyi (1944)
and, on the other hand, the interlocked trajectories of the Earth Sys-
tem and socio-political-economic system as presented by Steffen led
historian J.R. McNeill to suggest the term ‘The Great Acceleration’ in
homage to Polanyi (see also McNeill and Engelke, 2014).
The Dahlem Workshop proceedings were published in 2007 (Cos-
tanza et al., 2007). The first published use of the term Great Accelera-
tion in this sense (based on data from the Millennium Ecosystem
Assessment, the Intergovernmental Panel on Climate Change [IPCC]
and other sources) appears in Chapter 18 of these proceedings after a
discussion of many changes in the global environment: “The trends in
carbon dioxide (CO ) emissions and associated temperature changes
also suggest a rapid acceleration of human impacts on the atmosphere
over the last 50 years. These and many other changes demonstrate a
distinct increase in the rates of change in many human–environment
interactions as a result of amplified human impact on the environment
after World War II – a period that we term the ‘Great Acceleration’”
(Hibbard et al., 2007, p. 342). Steffen et al. (2007), in a paper that
arose from the same workshop, also used the term and concept ‘The
Great Acceleration’ in this same sense.
It was nonetheless clear from the discussion leading to the term
‘Great Acceleration’, and its utilization in publications, that the term
was not intended for use in a precise mathematical sense but rather
metaphorically to describe great changes in both Earth System indica-
tors and related drivers in the socio-political-economic system post-
1950. However, we acknowledge that ‘acceleration’ is open to misin-
terpretation as a mathematical construct or indeed in other ways, and
that ‘rapid increase’ would be more descriptive (Nielsen, 2021b suppl.
p. 7), but the term is now entrenched in the literature and there is no
obvious replacement.
0
200
400
1870
1880
1890
1900
1910
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2010
Year
TWh
Global energy consumption
a)
5
0
5
1870
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2010
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%
Annual growth rate of energy consumption
b)
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10000
15000
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$
Global GDP per capita (2011 US$)
c)
6
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Annual growth rate of GDP per capita
d)
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Global population
e)
0.0
0.5
1.0
1.5
2.0
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1890
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%
Annual growth rate of population
f)
Figure 2. Major drivers of the Great Acceleration. a, b) Global human energy consumption, where the red dashed line in (b) is the model
Nielsen (2018a, b, 2021a) proposed as being relevant up to ~1950. Note that important shorter-term variations in the rate of change are not
well represented by simple mathematical models. c, d) global productivity (GDP). e, f) Global population. All three drivers show significantly
increased rates at around 1950 and sustained positive (above zero) growth thereafter. The black line in b, d, and f represents a 10-year run-
ning average. Data sources: Maddison project database (2020) for population and GDP, and Steffen et al. (2015) for global human energy
consumption.
4
Revisiting the Great Acceleration Data
Even before the Great Acceleration data were assembled in the
early 2000s, Earth System scientists anticipated that a steady rise in
human pressure from around 1780 would support Paul Crutzen’s sug-
gestion that the Anthropocene started in the latter part of the 18 cen-
tury with the beginning of the Industrial Revolution in England
(Crutzen and Stoermer, 2000). An approximately linear growth would
then reflect a constant rate of change for each of the parameters over
this time. The discovery that the real data showed a slow rise through
the 19 and early 20 centuries followed by a significant increase in
the rate of change around the mid-20 century was therefore not
expected by the Earth System community, even though historians
were less surprised by the rapid increase in human activity and its
impacts from the mid-20 century onwards (e.g., McNeill, 2000).
The revealed pattern of a long and slow rise followed by what
appears to be a sudde n increa se is characteri stic of hyperbolic growth.
Nielsen emphasized this and concluded that because the growth pat-
tern is smooth, there are no sudden increases in growth rates that can
be used to support the beginning of the Anthropocene. However,
whether a hyperbolic trend is the best fit for the Great Acceleration
data up to around 1950 or not has limited relevance for the Great
Acceleration and the Anthropocene for several reasons.
It obscures the large short-term variations present in the empirical
data, as can be seen in a plot of annual change in human energy con-
sumption (Fig. 2b) in which Nielsen’s proposed model is included.
Analysing the Great Acceleration curves as if they represent a simple
force growing progressively through time fails to account for the
complex array of socio-economic drivers evolving over many centu-
ries. This multifaceted history has been examined through a large
body of literature including books entirely devoted to the social
dynamics of 20 century environmental change (e.g., McNeill, 2000;
McNeill and Engelke, 2014). In the context of the Anthropocene, it is
not important whether the high rates of change following 1950 were
reached through gradually increasing growth rates as suggested by
Nielsen, or if the increase was sudden. It remains that human societ-
ies experienced an unprecedented and exceptionally fast period of
growth in the decades following 1950. It misleads to label this time of
sustained fast growth a ‘deceleration’ simply because relative growth
rates did not continue to increase further.
Intervals of rapid growth should be time-limited, but Nielsen
(2018a, b, and 2021a) apparently considered that any rapid growth
used to support the Anthropocene should extend from the mid-20
century to the present day, rather than being a short-lived, immedi-
ately post-World War II event. In fact, many of his results show con-
tinuation of the proposed historical trajectory through the 1950s, and
examples of deceleration tended to be towards the later decades of the
20 century (see table 1 of Nielsen, 2021a) which could be consistent
with a mid-20 century rapid increase in growth. The notion that rapid
growth would be a short-lived, albeit transformational, event in the
Great Acceleration graphs was already recognised in the original doc-
umentation in the IGBP synthesis book (Steffen et al., 2004). Nielsen
(2018a, b, and 2021a) cited the IGBP book but did not refer to the
possible future trajectories clearly outlined within it (Figs. 3.66 and
3.67 on pages 132–133, and Fig. 3.69 of Steffen et al., 2004).
The stylized graph in the IGBP book (Fig. 3) was intended, as with
the Great Acceleration graphs, only to serve as a visual representation
of the large magnitude of changes occurring in the Earth System, and
of the fact that their human drivers could not continue indefinitely.
That is, any rapid acceleration must necessarily be short-lived: it was
suggested to occur only during a short interval around the mid-20
century and in the few decades thereafter. In fact, trajectories a and b
of Fig. 3 are logistic curves in which there is an inflection represent-
ing the point at which the growth rate reaches its maximum (Smil,
2019). In Nielsen (2021a), the inflection point is synonymous with
‘deceleration’. The change in growth rates must therefore by defini-
tion be highest in the 1950s and 1960s just prior to the ‘decelera-
tions’, supporting the initial interpretations of the Great Acceleration.
While the relative growth of many indicators slowed in the 1970s
(e.g., Fig. 2b, d and f), they crucially remain positive, and extremely
rapid compared to earlier centuries, with the consequence being that
the magnitudes, and associated pressures exerted by humanity on crit-
ical Earth System processes, have continued to increase. In absolute
terms, these pressures and their impacts are increasing faster today
than at any other time in history (IPCC, 2021). One manifestation of
this is seen in the continued rapid accumulation of CO in the atmo-
sphere (Fig. 4).
The resulting increases in magnitude are what give the Great
Acceleration its enormous impact on the Earth System. The original
Great Acceleration curves (Steffen et al., 2004, 2015) were simple plots
showing changes in magnitude over time, and this depiction remains
sufficient to identify a rapid and unmistakable change since 1950.
Nielsen underestimated this change in scale: “Human impacts and
activities are now strong but it is questionable whether they are strong
enough to cause a transition to a new geological epoch, particularly
because, in general, they were becoming weaker from the 1950s or
even earlier” (Nielsen, 2021a, p. 6). We emphasize that the impacts
and activities of humans have not become weaker simply because
they grew more slowly.
Human pressure on the Earth System grew significantly from 1950
to 2019. For example, the amount of cement produced per year has
Global change process
Past Present Future
a
b
c
Inflection point
Figure 3. Three trajectories, stabilisation (a), collapse (c), and an
intermediate trajectory (b), proposed by Steffen et al. (2004, fig. 3.69)
to bracket the range of possible futures. The inflection point indi-
cates when the rate of change goes from increasing, i.e., changing
faster and faster, to decreasing, changing more slowly.
5
increased 32-fold between 1950 and 2015, from 130 Mt in 1,950 to
4,180 Mt in 2015 (Syvitski et al., 2020; Table 1). This enormous
increase in magnitude means that even though global cement produc-
tion rates have not increased since 2015 (Fig. 5), the amount of cement
used, and the associated impacts on the Earth System, were higher in
the last decade alone (2010–2019) than during the entire 20 century.
Cement production is of particular significance both to the Great
Acceleration and to the Anthropocene for two reasons. Firstly, it is a
significant contributor to atmospheric CO which is released through
the calcination process used in its manufacture (CaCO [limestone] +
heat → CaO [lime] + CO ) together with CO produced from the
energy required to heat limestone. Secondly, most cement is used for
concrete production, with approximately 15% of average concrete mass
consisting of cement (Waters and Zalasiewicz, 2018). This requires
the excavation of much larger volumes of aggregate (sand, gravel, etc.)
which contributes proportionally to changes in the global sediment
budget. Concrete also contains components that mark modern cement
as a new rock-like material, linking it directly with the geological
expression of the Anthropocene (Waters and Zalasiewicz, 2018).
Unsurprisingly, the production of cement (Fig. 5) is closely linked with
the post-World War II expansion of the built environment and with
other key environmental parameters. Table 1 shows the striking increase
in scale for many of these parameters.
Similarly, an analysis of Earth’s sediment cycle, which is the very
foundation of stratigraphy, reveals the overwhelming dominance of
modern industrial activity (Syvitski et al., in press). The global sedi-
ment flux presently exceeds 300 Gt/y, of which >96% results from
human activity. This is the mass equivalent of each human moving
~37.5 metric tons per year. It compares with estimated values of around
73 Gt/y for ~1950, 11 Gt/y for the post-glacial Holocene, 22 Gt/y for
the deglacial Holocene, 11.4 Gt/y for the Quaternary, and 5 Gt/y for
the Phanerozoic Eon. These estimates imply that the sediment flux is
presently at a rate rarely if ever attained in 541 million years of Earth
history (Syvitski et al., in press).
Nielsen’s strong focus on relative changes in Great Acceleration
data (Nielsen, 2018a, b, and 2021a) fails to address the significance of
magnitude, which has extended aspects of the Earth System far beyond
the natural variability of the Holocene.
0
1
2
3
1750
1770
1790
1810
1830
1850
1870
1890
1910
1930
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1970
1990
2010
Year
ppm/y
Change in atmospheric CO2 concentration
Figure 4. Change in atmospheric CO concentration over time. The black line represents a 10-year running average. CO represents a major
Earth System response to the drivers of the Great Acceleration. This provides a clear illustration that concentrations have been rising at
increasing rates since ~1950. Data sources: Syvitski et al. (2020) up to 1980, NOAA Global Monitoring Laboratory (2021) for 1980–2020.
Tab le 1. T he G re at A cc el e ra ti on r ef le ct e d in t he e xc ep ti o na l in cr ea se i n m ag ni tu de o f ke y e nv ir on me nt al p ar a me te rs f ro m 19 50 t o 2015 (see Syvitski et
al., 2020 for primary data and sources)
Indicator 1900 1950 2015 Relative increase since 1950 (%)
Population (×10 )164324997349194
Global energy consumption (EJ/y) 41 100 514 414
Global GDP (billions 1990 Int’l $/y) 1116 4656 73,902 1487
Global reservoir capacity (km )1970515,534 2103
Number of dams 1587 7361 50,346 584
Plastic production (Mt/y) 0 2 381 18,950
Cement production (Mt/y) 5 130 4180 3115
NH production (Mt/y) 0 2 175 8650
Copper production (Mt/y) 0.50 2.38 19.10 703
Iron and steel production (Mt/y) 35 134 1160 765
Aluminium production (Mt/y) 0 2 58 2800
6
The relationship between the magnitude of the drivers (and the rate
at which they change) and the responses of the Earth System to these
drivers is complex, has been examined in a large body of literature,
lies at the heart of contemporary Earth System science, and is not
amenable to simple mathematical analysis. Absolute rates of change
in the climate system (e.g., CO and temperature rise; Lear et al., 2020)
and in the biosphere (IPBES, 2019) are generally highest today. When
viewed in terms of resource utilization and corresponding outflows of
wastes and emissions, the Earth System has undergone significant
upturns in metabolism around 1950 and again from the beginning of
the 21 century (Krausmann et al., 2018). All these features indicate
that the mid-20 century was an absolutely critical period when the
Earth System began its clear departure from the Holocene envelope of
variability at increasing rates. This is how Earth System science defines
the time at which the Anthropocene begins, and it aligns with an
extensive array of stratigraphic signals (Waters et al., 2018).
Non-uniform Responses to the Great Acceleration
The Great Acceleration around 1950 is clearly marked by upturns
in population growth, GDP, energy consumption (Fig. 2) and many
other critical indicators, as discussed above. Some indicators, how-
ever, show declines in growth rate after 1950 owing to increasingly
limited resources, and others have their upturns delayed through feed-
backs in the Earth System. This range of responses was anticipated
(Fig. 3) and reflects the complexity of the Great Acceleration concept
as a planetary phenomenon.
The global total number of existing large dams (Table 1) and global
marine fish capture (Fig. 6) both show declines in growth rate towards
the end of the 20 century. This should not be interpreted as reflecting
declines in human impact. In the case of large dams (minimum 15 m
height above foundation), the number built has been limited by the
finite number of large rivers that can be dammed, and that limit is
0
1000
2000
3000
4000
1930
1940
1950
1960
1970
1980
1990
2000
2010
2020
Year
Mt
Annual production of cement
Figure 5. Annual production of cement, showing an initial rise ~1950. Crucially, the amount of cement produced per year has increased 31
times between 1950 and 2015. Data sources: Syvitski et al. (2020) up to 2014, International Energy Agency (2021) for 2015–2019.
1900 1950 2010
2000
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Year
1930 1940
1920
1910
Reconstructed catch (+discards)
Without Peruvian anchoveta
With Peruvian anchoveta
0
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80
40
Catch (106 t)
Figure 6. Global marine fish catch figures based on Pauly et al. (2003, light and dark blue lines) and Pauly and Zeller (2016, red line) which
includes discarded bycatch. Note a clear rise in the 1950s and 1960s, a reduced rate of growth in the 1970s to 1990s, and a decline from
around the year 2000. The increased rate of growth in the 1950s and 1960s cannot be sustained, despite improved technical innovations,
owing to the depletion of fish stocks.
7
being approached (Steffen et al., 2015). Regarding global marine fish
capture, an actual decline in numbers is recorded as global fish stocks
become depleted. Simply put, an exponential increase of fish capture
will inevitably lead to population crash (Pauly et al., 2003; Pauly and
Zeller, 2016; Sumaila et al., 2016). Overfishing will also potentially
have left a biostratigraphic signature in the form of assemblage
changes and reduced diversity both in the open oceans (Thrush et al.,
2016) and coral reef systems (Bellwood et al., 2004; Hughes et al.,
2017). Furthermore, bottom trawling modifies the benthos and destroys
sedimentary structures, the combined actions of which will be appar-
ent in the Anthropocene sedimentary record (Hiddink et al., 2006).
Given that bottom trawling is prevalent on all continental shelves,
yields about a quarter of the world’s wild seafood (Mazor et al., 2021
and references therein), and is now extending down the continental
slope, this stratigraphic signal is probably global in extent.
Other indicators have upturns that are delayed by complex feed-
back loops. Global temperature, for example, does not precisely follow
CO as its most rapid rise began around 1970 (Fig. 7). One explanation
is that the industrial processes responsible for the post-World War II
rises in the Great Acceleration graphs were based partly on the use of
production lines of the kind that formerly made war materiel. Diverted to
produce consumer goods, these production-lines and others rapidly
assembled using the same techniques to produce consumer goods
were crude and dirty, loading the air with aerosols that reflected solar
energy. An increased demand for electricity also led to a rise in aero-
sols owing to an increase in coal use and the use of fuel-oil to gener-
ate this electricity. Aerosol production was a factor in slowing the rise
in global temperature, especially between 1950 and 1980, temporar-
ily disconnecting it from rising CO leve ls (Smith et al., 2016 ; Haustei n et
al., 2017, 2019; Qin et al., 2020). The anthropogenic global warming
signal emerged in the mid-1970s only when clean air regulations came
into force more or less globally (Haustein et al., 2019). A second
explanation is that natural oscillations in the oceanic transfer of heat
through the North Atlantic by the Atlantic Meridional Ocean Circula-
tion led to heat storage in the ocean in the 1950s, and heat release to
the atmosphere in the 1980s and beyond (Chen and Tung, 2018).
These natural fluctuations in surface temperature reflect the internal
dynamics of the Earth System and are largely independent of the
effects of CO . These effects are superimposed upon the curve of rising
temperature attributable to rising greenhouse gases, which also
include water vapour derived from increas-
ing oceanic evaporation in a warming world.
All these effects led to a step-wise increase in
temperatures with plateaus of lower increase
followed by acceleration, such as the 1976 rise
followed by a slower rise between 1998 and
2012 (Medhaug et al., 2017; Cheng et al., 2021).
Nevertheless, paleoclimate data have quanti-
fied the emergence of anthropogenic warming
in all tropical oceans and the Arctic between
1948 and 1962, well before the emergence of
warming on many continental areas (Abram
et al., 2016). The Earth is currently in a new
accelerated phase of warming (Johnson and
Lym an, 2020 ). Thu s, slo w ocea nic an d r apid
atmospheric feedbacks played a role in climato-
logical time series, either averaging or delaying
some of the changes occurring around 1950–
60. But viewed over the 150-year record, there
will be an increase from a time reasonably
close to 1950–60. The most striking signal of
ongoing anthropogenic warming is the stor-
age of heat in the global oceans (IPCC, 2021).
Approximately 90% of the heat from global
warming resides in the oceans. Ocean heat
content started to rise more steeply just before
1950 and since then has penetrated to depths
of at least 2,000 m globally (Cheng et al., 2017;
Abram et al., 2019). At the same time, ocean
salinity has revealed an amplification in the
global water cycle over the past 60 years. The
fresher parts of the ocean are becoming fresher,
while the salty parts are becoming saltier, due
to a combination of ice melt in polar regions
and evaporation in tropical regions (Cheng et
al., 2020; Gould and Cunningham, 2021).
420
400
380
360
340
320
300
280
260
Atmospheric CO2 (ppm)
Upper limit of pre-Industrial CO2
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
Global Temperature Anomaly (°C)
2000
1950
1900
1850
2000
1950
1900
1850
a)
b)
Figure 7. Atmospheric CO and global surface temperature. a) Atmospheric CO concentra-
tions for 1850–2020; data sources as for Fig. 4: Syvitski et al. (2020) up to 1980, NOAA Global
Monitoring Laboratory (2021) for 1980–2020. b) Global land–ocean temperature index for the
years 1850–2019 from NASA’s Goddard Institute for Space Studies (GISS).
8
These oceanic impacts of warming during the Anthropocene are
affecting ocean currents through the key role salinity plays. Changing
patterns of heat transport in the Gulf Stream are already causing a
slowdown in the Atlantic Meridional Ocean Circulation that until
recently has warmed the North Atlantic between Newfoundland and
Ireland, where cooling now occurs (Caesar et al., 2021).
Atmospheric CO represents a major Earth System response to the
drivers of the Great Acceleration, and concentrations have been ris-
ing at increasing rates since around 1950 (Fig. 4). Even if anthropo-
genic CO em issions decli ne in t he future, atmos pheric CO con cent rat ion s
will remain high through equilibrium with the CO concentration in
the surface ocean. This is because a reduction in human emissions will
lead to an increase of CO emissions from the ocean to balance that loss.
“Equilibration with the ocean will absorb most of [the CO ] on a ti mesca le
of 2 to 20 centuries. Even if this equilibration were allowed to run to
completion, a substantial fraction of the CO , 20–40%, would remain
in the atmosphere awaiting slower chemical reactions with CaCO
and igneous rocks. The remaining CO is abundant eno ugh to conti nue to
have a substantial impact on climate for thousands of years.” (Archer
et al., 2009, p. 131). Global sea-level rise is similarly locked in for
centuries or millennia to come, even with emission reductions, and a
recent modelling simulation predicts global mean sea level to rise con-
tinuously over the next 10,000 years under all scenarios considered (Van
Breedam et al., 2020). Erosional and depositional processes associ-
ated with this global sea-level rise will therefore continue to operate
on a significant geological time scale.
Implications of the Great Acceleration for an
Anthropocene Epoch
The Great Acceleration is a truly interdisciplinary concept and in
this context is being examined for its stratigraphic usefulness by the
AWG (s ee b el ow ). We h av e s ho wn t ha t ma ss iv e i nc rea se s i n t he
growth of global socio-economic indicators and Earth System trends
that represent the Great Acceleration are a real and striking phenome-
non, with major geological consequences.
The Great Acceleration provides the narrative for a new interval of
geologic time starting in the mid-20 century, while also establishing
the framework enabling the scale of critical Earth System drivers to
be placed in context. Among the most potent of these drivers are
atmospheric CO and m ethane ( Fig. 8).
The global average atmospheric CO concentration in 2019 was
409.8 ± 0.1 ppm (Lindsey, 2020), more than 100 ppm higher than the
highest concentration prior to the 20 century during the past 800,000
years of Antarctic ice core records. Modeling studies indeed suggest
that concentrations are now higher than they have ever been during
the past three million years (Willeit et al., 2019), and proxy records
imply that CO concentrations had not attained present levels since
about 14 Ma in the Middle Miocene (Zhang et al., 2013) or perhaps
even earlier (Cui et al., 2020). The rate of increase in atmospheric CO
concentration rose sharply from the mid-20th century to the present,
on average about 100 times greater than the rate of increase from the
Late Pleistocene to the Early Holocene (Zalasiewicz and Waters,
2019; Lindsey, 2020).
With respect to methane, over the past 800,000 years of Antarctic
ice core records, levels had never exceeded ~800 ppb (Loulergue et
al., 2008) but reached 801 ppb in 1850, were at 1,162 ppb in 1950,
and 1,858 ppb in 2018 (Our World in Data, 2020; Fig. 8). These
increases in CO and methane do not represent anthropogenic emis-
sions exclusively as they reflect a planetary response to a wide range
of human impacts. The global human population responsible for these
changes has risen from 1,643 million in 1900, to 2,499 million in
1950, and 7,349 million in 2015 (Syvitski et al., 2020; Table 1).
The analysis of changing socio-economic trends is not strictly rele-
vant to the definition of the Anthropocene as a chronostratigraphic
unit, but it provides the narrative framework for the Anthropocene
concept, in that socio-economic drivers, from the mid-20 century
onwards, have significantly perturbed Earth System signals beyond
the envelope of Holocene norms, just as asteroid impact-driven pro-
cesses dramatically perturbed the Earth System from a Cretaceous to
a Paleogene state 66 million years ago.
While the appropriate mathematical analysis of Earth System and
socio-economic trends might yield useful information about underly-
ing process-based causes, geological signals are rarely suited to the
same scrutiny because they carry uncertainties in age modeling, dia-
genetic effects, taphonomic processes and so on. Instead, a more prac-
tical approach is used to identify marked upturns or downturns in a
signal without considering its fit to a hyperbolic, exponential, or any
other hypothetical curve.
The subdivision of the Holocene (Fig. 9) exemplifies this approach.
The base of the Holocene Series (and Lower Holocene Subseries and
Greenlandian Stage) is defined by a GSSP in the Greenland NGRIP2
ice core (Walker et al., 2009, 2018, and 2019). The GSSP is marked
by an ‘abrupt decline’ in deuterium excess values that is clearly visi-
ble in the data plots without statistical analysis (Fig. 9a). This decline
represents a rapid (≤ 3 yr) northward retreat of the oceanic polar front,
signalling a major climatic shift during the more protracted warming
from glacial to interglacial conditions. This northward (warming) shift of
the sea-ice margin in the North Atlantic paradoxically now caused mois ture
precipitating over Greenland to be sourced from higher (colder) lati-
tudes (Walker et al., 2009). The GSSP is placed near the midpoint of
the steepest part of this shift in deuterium excess values. Attempting
to fit this plot to a hyperbolic or exponential curve is neither realistic
nor meaningful.
The base of the Northgrippian Stage (and Middle Holocene Sub-
series) is traceable globally via a pronounced climatic event at 8.2 ka.
This event is marked by a brief shift to more negative δO values in
the Greenland NGRIP1 ice core that hosts the GSSP (Fig. 9b) coinci-
dent with an abrupt cooling event. In detail, however, the GSSP aligns
with a geochemical signal of volcanic activity during the 8.2 ka cli-
matic event, allowing precise correlation with other Greenland ice
cores (Walker et al., 2018, 2019). Its position was not chosen with
regard to the internal geometry of the δO shift even though this rep-
resents the primary guide for global correlation of this chosen level.
The GSSP defining the base of the Meghalayan Stage (and Upper
Holocene Subseries) is placed approximately midway between two
abrupt successive shifts to less negative δO values in the KM-A spe-
leothem (Fig. 9c), indicating abrupt reductions in precipitation. This
‘mid-point’ approach follows established practice without requiring
detailed mathematical analysis of the data across this interval (Walker
et al., 2018, 2019; Head, 2019). Such analysis would be pointless
9
given the ‘noise’ within any single δO speleothem signal, and these
signals may vary even within the same cave system. The precise posi-
tion of this boundary was chosen to coincide with 4.2 ka on the time
scale used, which was of more practical use in this instance.
The validity of these (and all the other) formal chronostratigraphic
units does not therefore depend on the mathematical testing of the
stratigraphic signals used to characterise them, as the practical use of
these units to Earth scientists has long been shown by their effective
and systematic application in day-to-day work.
Defining any unit of the Geological Time Scale and documenting
0
10
20
30
40
80
200
400
1000
1600
CH
4
concentration (GRIP)
300
400
200
Pleistocene Holocene
Age (thousand years)
Anthropocene
-7.5
-8.0
-8.5
150
Greenlandian Northgrippian Meghalayan
-6.5
-7.0
13
C (average ± 2) (EPICA Dome C)
13
C (‰) (Law Dome)
CO
2
concentration (EPICA Dome C)
Early Middle Late
Late
20 18 16 14 12 10 8 6 4 2 0
CH
4
(ppb) CO
2
(ppm)
NO
3
-
(ppb)
120
160
NO
3
-
(Summit)
15
N-NO
3
-
15
N-NO
3
-(‰)
13
C (‰)
0
-2
-4
-1
-3
Temperature anomaly (°C)
a)
b)
c)
d)
250
350
Figure 8. Key trends and drivers for the Anthropocene from the Late Pleistocene to present, based on ice core records from Greenland
(Greenland Ice Core Project [GRIP], Summit) and Antarctic (European Project for Ice Coring in Antarctica [EPICA] Dome C, Law Dome)
and modern instrumental data (a–c, adapted from figs. 1 and 2 respectively of Zalasiewicz et al., 2018, 2019b). d) Global temperature anoma-
lies (mean and one standard deviation) relative to the 1980–2004 mean are adapted from Clark et al. (2016). Relative stability characterises
the Holocene, and sharp deflections the Anthropocene. The start of the Anthropocene in the mid-20 century contrasts with the relatively
gradual changes, at this scale, across the Pleistocene–Holocene boundary. Despite the global temperature rise during the Pleistocene–Holo-
cene transition being of greater magnitude, the rate of rise over the past century of 1.25 C far exceeds the average of 0.05 C per century over
the ~7000 year warming during the Late Pleistocene–Early Holocene transition.
10
89101112131415
GICC05 timescale (ka b2k)
18O (‰)
Early Holocene
a)
14861487148814891490149114921493149414951496
NGRIP2 depth (m)
11.6011.6511.7011.7511.80
5
10
15
GICC05 timescale (ka b2k)
18O (‰)
Late Pleistocene
8.2 ka
event
Middle
Holocene
13241328133213401344
38
37
36
35
34
33
GRIP depth (m)
12201224122812321236
NGRIP1 depth (m)
133313341335
0
2
4
6
GRIP depth (m)
ECM (µequiv. [H+]
1334.04
1227122812291230
NGRIP1 depth (m)
1228.67
1336
18O (‰)
Late Pleistocene Early Holocene
Early Holocene Middle Holocene
3.83.94.04.14.24.34.4
3.74.5
-7.5
-7.0
-6.5
-6.0
-5.5
-5.0
-4.5
18O (‰)
Onset
4303±26
4071±31
GSSP
4.200±30
Termination
3888±22
Early Holocene Middle Holocene
Middle Holocene Late Holocene
b)
c)
GSSP
GSSP
Figure 9. Chemical (climatic) indicators used to recognise and subdivide the Holocene Series/Epoch. A green line represents the position of the
Global boundary Stratotype Section and Point (GSSP) in each case. a) Base Holocene Series and base Greenlandian Stage, defined by GSSP in
the North Greenland Ice Core Project (NGRIP) 2 ice core at a depth of 1492.45 m, placed within an overall trend towards less negative δO val-
ues (upper panel) and precisely at an initial abrupt decline in deuterium-excess values (lower panel). The Greenland Ice Core Chronology 2005
(GICC05) used here is expressed in years before 2000 CE (b2k). b) Base Northgrippian Stage, defined by GSSP in the NGRIP1 ice core at a
depth of 1228.67 m, placed within the ‘8.2 ka climatic event’ as expressed by more negative δO values (upper panel) and precisely at a double
acidity peak reflected by electrical conductivity measurements (ECM) and representing a strong volcanic signal. c) Base Meghalayan Stage,
defined by GSSP in the KM-A speleothem, Meghalaya, India at a depth of 7.45 mm from its unweathered distal end (Head, 2019), and placed at
4.2 ka on the timescale used, which coincides with the approximate midpoint of a two-step shift to less negative δO values and signals a decrease
in monsoon rainfall. It would not be appropriate, helpful or informative to analyse these signals, used to place the GSSPs that define the Holo-
cene and its subdivision, by means of continuous mathematical functions. (Adapted from Walker et al., 2018, 2019; Head, 2019).
11
its contents can be accomplished only using evidence from the rock
record and other geological archives (Salvador, 1994; Remane et al.,
1996), as noted by Nielsen (2021b). However, changes to the Earth System
state often provide the underlying rationale to justify the introduction and
rank of a new unit of geological time. The traditional evidence for such
changes in state has been exclusively geological (e.g. paleontology
revealing mass extinction events) – but historical and instrumental
records must be included when available as they too represent geolog-
ical time. The Great Acceleration offers not only this justification for
the Anthropocene and its rank, indeed with unsurpassed detail, but it
has also given rise to a multitude of signals indelibly preserved in the
geological record.
Ongoing Analysis of the Anthropocene as a Poten-
tial Unit of the Geological Time Scale
In 2009, the Subcommission on Quaternary Stratigraphy, a constit-
uent body of the International Commission on Stratigraphy (ICS),
established the Anthropocene Working Group (AWG) to evaluate the
Anthropocene as a potential unit of the International Chronostrati-
graphic Chart upon which the Geological Time Scale is based. An
early priority of this working group was to examine a wide range of
existing geological, historical and instrumental data sets, with the pur-
pose of determining whether the Anthropocene had appropriate expres-
sion in the geological record, when might best represent the onset of
the Anthropocene, and whether the originally proposed rank of epoch/
series was justifiable. The approach, although focused on geology,
was multidisciplinary, reflecting the overlap of geological and histori-
cally observed time and process in this interval with a correspond-
ingly diverse AWG membership (Zalasiewicz et al., 2017a). The initial
suggestion of a late 18 century onset for the Anthropocene (Crutzen
and Stoermer, 2000; Crutzen, 2002) was followed by Steffen et al.
(2007) who subdivided the Anthropocene into three stages, linking
the Great Acceleration to a ‘stage 2’, and with ‘stage 3’ being a con-
sideration of potential future scenarios (see also Steffen et al., 2011).
However, Zalasiewicz et al. (2014) provisionally used the Great Acceler-
ation to recognise the beginning of the Anthropocene, dated at approx-
imately 1950. This conceptual link between the Anthropocene and the
Great Acceleration was affirmed by the AWG shortly thereafter (Zala-
siewicz et al., 2015). Indicative voting within the AWG in 2016 con-
firmed support for the Anthropocene as a stratigraphically substantiated
unit, and that it should be defined by a Global boundary Stratotype
Section and Point (GSSP) and formalized at the rank of epoch with an
inception at ~1950 CE (Zalasiewicz et al., 2017b). A binding vote by
the AWG in May 2019 addressed two critical questions: should the
Anthropocene be treated as a formal chronostratigraphic unit defined
by a GSSP, and should the primary guide for the base of the Anthro-
pocene be one of the stratigraphic signals around the mid-20 century
of the Common Era (CE)? Each vote was carried decisively with 29 in
favour, 4 against, no abstentions; with 34 potential voting members
(one ballot not returned). Selecting a marker event of optimal correla-
tion potential in advance of the GSSP itself follows normal strati-
graphic practice (Remane et al., 1996). The Great Acceleration, with its
multitudinous stratigraphic and other signals and magnitude of
change, is central both in characterizing the base of the Anthropocene
and in justifying its proposed series/epoch rank. If the Anthropocene
as currently envisioned by the AWG, and its corresponding stage/age,
are approved by the ICS and ratified by the Executive Committee of
the IUGS, they will terminate the Holocene Series/Epoch and the
Meghalayan Stage/Age respectively, and the Anthropocene will con-
stitute a third series/epoch for the Quaternary System/Period (Fig. 1).
The Great Acceleration, however, does not define the chronostrati-
graphic base of the Anthropocene – only a GSSP can do this (Salvador,
1994; Remane et al., 1996). The geological expression of the Anthro-
pocene is now documented (e.g., Waters et al., 2016, 2018; Zalasiewicz
et al., 2019b), and 12 GSSP candidate sections are being examined for
their suitability to record stratigraphic signals around the mid-20
Antarctic
Peninsula
San Francisco
Bay
Searsville
Reservoir
Crawford
Lake
Baltic Sea
Sudetes
Ernesto
Cave
Gulf of
Mexico
Great Barrier
Reef
Longwan Maar Beppu Bay
Vienna
Anoxic marine basin
Estuary/coastal
Coral
Lake
Peat
Ice sheet
Speleothem
Anthropogenic
KEY
Figure 10. Location of candidate GSSP localities currently under investigation indicating the depositional environment. Satellite image:
NASA Visible Earth.
12
century (Figs. 10, 11). Archives being explored include an ice core
from Palmer Land on the Antarctic Peninsula, lake sediments from
California (USA), Ontario (Canada) and Jilin Province (China),
coastal sediments from California (USA) and Kyushu Island (Japan),
marine sediments from the Baltic Sea, a peat sequence from the Sude-
tes Mountains (Poland), corals from the Great Barrier Reef (Austra-
lia) and Gulf of Mexico (USA), a speleothem from the Trentino
region (Italy) and anthropogenic deposits from Vienna (Austria). A
further suggestion to use dendrochronological records by Waters et al.
(2018) has not progressed to the analysis of a candidate GSSP, although
Turney et al. (2018) suggested using a non-native Sitka spruce from
Campbell Island, New Zealand. However, their proposal provided
just one signal, carbon-14 for only a six-year duration through the
peak of the bomb-spike, failing to record the onset of the signal or any
proxy data characterising the Holocene–Anthropocene transition. Most
sites are in borehole cores, although the Vienna site also includes a
trench section, and one site is represented by a stalagmite (the Ernesto
speleothem). Many of the sites show annually to sub-annually resolved
laminations (Crawford and Longwan Maar lakes, Beppu Bay coastal
sediments, the Gulf of Mexico and Great Barrier Reef corals, the Ant-
arctic Peninsula ice core and the Ernesto Cave speleothem) that can
be independently dated radiometrically to confirm a complete succes-
sion extending to pre-Industrial times. The Anthropocene compo-
nents of the sections range from as little as 5 mm for the speleothem to
about 34 m for the ice core.
Earth System trends that characterise the Great Acceleration are
unsurprisingly closely aligned to the signals that are being considered
within geological archives, although often only through proxies
(Zalasiewicz et al., 2017c). Archives of carbon dioxide, nitrous oxide
and methane concentrations predating the 1950s can only be deter-
mined from glacial ice (Fig. 8), such as the Palmer ice core (with the
exception of rare atmospheric CO measurements dating to the 1880s;
Summerhayes, 2008), and are unsuitable for correlation within other
geological successions. More practical for correlation across diverse
environments is the analysis of trends of stable carbon and nitrogen
isotopes (not discussed by Nielsen, 2021a, b; see Fig. 8a and 8c) and
Anthropocene Working
Group GSSP Sites and
Analyses (Oct. 2021)
Gotland Basin, Baltic Sea
San Francisco Estuary, USA
Beppu Bay, Japan
Searsville Reservoir, USA
Crawford Lake, Canada
Sihailongwan Lake, China
Flinders Reef, Australia
Gulf of Mexico, USA
Antarctic Peninsula ice core
Ernesto Cave speleothem, Italy
Anthropogenic sediments,
ITRAX, CT scan, grey scale etc.
KE
Y
210
Pb dating Proposed
137
Cs,
134
Cs,
241
Am Processing
238, 239, 240
Pu isotopes Completed
14
C (and A-bomb pulse)
Pb isotopes
C and N stable isotopes
Fly-ash (SCPs)
Metals (and / or Hg)
Microplastics
PAHs, PCBs, DDT, POPs, VOCs etc.
Pigments/biomarkers
Black carbon
Oxygen isotopes
Boron isotopes
CO
2
, CH
4
/S, SO
42
(ice/speleothem)
Trace (Ca/Sr)
Fossils
Diatoms
Foraminifera
Ostracods
Molluscs
Pollen
Phytoliths
Zooplankton
Testate amoebae
Othe
r
eDNA
Faecal biomarkers
Fish scales
Vienna, Austria
Figure 11. The range of stratigraphic markers as of 25th October 2021 being investigated at the 12 candidate GSSP sites. The following
abbreviations are used: CT=computed tomography, SCPs=spheroidal carbonaceous particles, PAHs=polycyclic aromatic hydrocarbons,
PCBs=polychlorinated biphenyls, DDT=dichlorodiphenyltrichloroethane, POPs=persistent organic pollutants, VOCs=volatile organic com-
pounds, and eDNA=environmental deoxyribonucleic acid.
13
which are to be analysed across most of the candidate GSSP sites,
except the ice core, speleothem and anthropogenic deposits (Fig. 11).
Temperature anomaly trends of modern times are based on combined
land and ocean observations, not on geological records which rely on
investigating proxy signals such as stable oxygen isotopes which are
to be investigated in the candidate GSSP ice core, speleothem, and
corals (also with Sr/Ca ratios in the last of these). Temperature records
can also be determined from growth extension rates in dendrochrono-
logical records (Fig. 8d), although no such candidate site is currently
being considered. Similarly, present ocean acidification trends are
based upon direct ocean measurement, and to trace this record
through geological time it is necessary to analyse the proxy signal of
δB isotopic records in foraminiferal and coral carbonates (including
the two coral candidate sites), or through the effect on biotic assem-
blages. Changes in stratospheric ozone have no physical geological
expression other than traces in polar ice; but global values for marine
fish capture, global shrimp production, loss of tropical forests, and
changes to global agricultural land area may be recorded in geologi-
cal archives through changes in biotic marine and terrestrial assem-
blages (e.g., recorded for example by sardine and anchovy scale
deposition rates at the Beppu Bay site in Japan) and increased erosion
leading to greater sediment accumulation rates (e.g., strikingly seen in
Fontanier et al., 2018).
Potential primary markers include the presently favoured nuclear
fallout-derived plutonium-239 record. Its initial rise as detected in
sediments appears near-isochronous and near-global in extent, as required
for optimal correlation. This signal, almost exclusively anthropogenic in
origin, is dated to ~1952 CE based on its presence in sediments and
other geological materials and reflects its pronounced rise in produc-
tion at this time (Waters et al., 2015, 2019). Plutonium is being anal-
ysed for all sites, except the speleothem GSSP candidate (Fig. 11),
and can be used in conjunction with other radionuclides, including the
naturally occurring carbon-14, which shows an abrupt upturn from
~1955 in response to atmospheric nuclear tests. It is nonetheless the
array of stratigraphic signals associated with the Great Acceleration
(Zalasiewicz et al., 2017c) that in practice would allow routine recog-
nition of the base of the Anthropocene in many diverse natural
archives and environments (Waters et al., 2018; Zalasiewicz et al.,
2019b) and which to varying degrees are present at the candidate
GSSP sites (Fig. 11). Such signals include the appearance of micro-
plastics (Zalasiewicz et al., 2016; Bancone et al., 2020), upturns in
abundance of fly-ash (Rose, 2015) and black carbon (Han et al., 2017),
increased lead abundance and perturbed lead isotopes (Reuer and
Wei ss , 2 00 2), in cr eas ed ab un dan ce of p er si st en t or ga ni c co mp ou nd s
such as PCBs and novel pesticides (Gałuszka et al., 2020), nitrogen
isotope patterns (Holtgrieve et al., 2011), and many other geochemi-
cal signals (Waters et al., 2018, also see below). The stratigraphic dis-
tributions of biotic species can also be used as an important correlation
tool, though typically lacking the globally isochronous markers required
for the Anthropocene (Williams et al., 2018). Certainly, they can be
used as further supportive evidence for the onset of the Anthropocene
(e.g., Wilkinson et al., 2014) with unprecedented floral and faunal
changes in response to a broad array of factors, including human-
induced climate change, pollution, deforestation, over-predation, introduc-
tion of domestic species and of non-indigenous species (spectacularly
seen at the San Francisco Bay candidate site) as well as increased
rates of species extinction and extirpation. The analysis of candidate
GSSP lake and coastal sites includes an array of diatoms, foraminifera,
ostracods, molluscs, pollen, phytoliths, zooplankton, testate amoebae
as well as fish scales and emerging biomarkers (Fig. 11).
Given the scale of change registered in atmospheric carbon diox-
ide, methane, nitrates and atmospheric and ocean temperatures (Fig.
8) and many other planetary indicators when compared with the much
smaller transitions across the subseries boundaries of the Holocene
Series/Epoch (Fig. 9), it would be difficult, as argued by Waters et al.
(2016), to rationalise a rank lower than series/epoch for the Anthropo-
cene. In fact many of these parameters have 200 to 300% variances or
larger compared with the Holocene Epoch and some represent phe-
nomenological changes without precedent in the Holocene including
a more acidic ocean and dispersal of novel materials (Syvitski et al.,
2020). It has been proposed that defining the Anthropocene at system/
period rank, based upon the scale of species extinctions and increas-
ing CO and temperatures, is more consistent with previous geologi-
cal boundaries in the Phanerozoic (Bacon and Swindles, 2016). This
is based upon an assumption that current extinction rates far exceed
background geological levels and are on a trajectory towards a sixth
mass extinction event (Barnosky et al., 2011), with previous such
events used as the framework (if not specific markers) to justify estab-
lishment of boundaries at system/period (Ordovician–Silurian, Devo-
nian–Carboniferous and Triassic–Jurassic) or erathem/era (Paleozoic–
Mesozoic and Mesozoic–Cenozoic) ranks. However, this relies upon
a near-future rather than current assessment of the situation. Many
key Earth System parameters remain within the Quaternary envelope
of variation and at present there is no clear argument that the Quater-
nary System/Period should be terminated.
Final Considerations
The Great Acceleration of the mid-20 century, from an array of
Earth System and socio-economic indicators, was never intended to
represent strict mathematical acceleration, but to reflect the striking
increase in the magnitudes of these indicators, and the implication of
such change (Steffen et al., 2004, 2015; Hibbard et al., 2007). Chal-
lenges to the concept of the Great Acceleration and hence of the
Anthropocene (Nielsen, 2018a, b, and 2021a, b) do not consider the
broader descriptive uses of the term ‘acceleration’, relying instead on
curve-fitting methods that underestimate Earth System complexity
and the implications of environmental loadings, and they misunder-
stand the process used in defining formal chronostratigraphic/geo-
chronologic units.
Nielsen’s (2018a, b, and 2021a) analyses usefully identify an
inflection point (Fig. 3) for many of the Great Acceleration indica-
tors. This point generally occurs at around 1960 or later (Table 1 of
Nielsen, 2021a), which means that the highest growth rate observed
must be just before that point in the time series. Evidence for the
Great Acceleration, occurring in the decade or so following ~1950, is
apparent within Nielsen’s own analyses.
The notion of a ‘Great Deceleration’ in the mid-20 century (Niel-
sen, 2018a, b, and 2021a, b) is simply an expected consequence of a
marked acceleration – in the real world, hyperbolic rises cannot be
sustained over long durations (Smil, 2019). Importantly, a decelera-
14
tion does not preclude continued increase in parameter growth, even
if the growth rate is reduced. The consequent magnitude of increase
among key indicators of the Earth System depicts a planetary trajec-
tory that departed from the envelope of Holocene variability in the
mid-20 century and argues for an Anthropocene at the rank of series/
epoch.
The Anthropocene from an Earth System perspective represents a
complex planetary response to human impact involving lags, abrupt
shifts and feedback loops. Nevertheless, there is strong evidence that
around the mid-20 century many important Earth System parame-
ters began strong trajectories away from Holocene norms (Steffen et
al., 2016). Human impacts have a long and attenuated history that can
be traced into the Late Pleistocene, but they did not become an over-
whelming global environmental force until the mid-20 century.
From the wide array of proxy signals marking this striking Earth
System change, a single primary stratigraphic marker must be chosen
that will enable precise global correlation of the base of the Anthropo-
cene. This signal has yet to be decided, but plutonium-239 is promis-
ing. It arises locally in 1945 CE from the atmospheric detonation of
atomic (fission) devices, followed by a globally distributed and detect-
able signal in geological archives arising from the atmospheric test-
ing of the much higher yield thermonuclear (fusion) devices from
1952 CE. If such a signal were adopted, it would be on the basis of
stratigraphic utility alone, avowedly decoupled from the atomic age
and all this connotes, albeit loosely linked by association with the overall
rise in technology in the mid-20 century. Should it be chosen, this
signal would be accompanied by many secondary stratigraphic mark-
ers more closely associated with the drivers of the Anthropocene.
We e mph as iz e t ha t t he G re at A cce le ra ti on c ann ot i ts elf d ef ine a
new unit within the Geological Time Scale: only a GSSP can do this.
But it provides a crucial break of appropriate magnitude in the narra-
tive of Earth history to justify inclusion of the Anthropocene at the
rank of series/epoch beginning in the mid-20 century. The Great
Acceleration has also left a constellation of stratigraphic signals, of
which just one would serve as the primary guide to the GSSP. The
others would provide abundant help in characterizing the Anthropo-
cene and in practical recognition of its deposits.
The brief (~70-year) duration for the Anthropocene and its useful-
ness require comment. Formal units of the Geological Time Scale are
defined only by their base and no minimum duration is stipulated. The
Anthropocene as a formal unit would be ongoing, as is presently the
case for the Holocene Epoch and Late Holocene Subepoch (Megha-
layan Age). The Holocene (duration presently 11,721 years) and its
subepochs (duration as little as 3,464 years) are the briefest units for
their rank, and attest to the needs and capabilities of exceptionally pre-
cise chronostratigraphy in the Quaternary (Head, 2019). The Anthropocene
follows this tradition. The utility of these units cannot be doubted judging
from citation figures. The term ‘Late Holocene’ was cited 654 times
in the year 2020, and the term ‘Anthropocene’ 1,240 times in spite of
its short duration and comparative novelty, as compared with ‘Silurian’
cited just 471 times (Clarivate’s Web of Science). The final duration
of the Anthropocene is obviously unknowable, and chronostratigra-
phy is based on the past, not the future. But it may be relevant that the
IPCC (2021) considers some changes brought about by global warm-
ing, including sea-level rise, to be irreversible over hundreds to thou-
sands of years. Perhaps more important than the duration of a formal
unit in the Geological Time Scale is its stratigraphic content. Anthro-
pocene deposits are exceptionally accessible and widely distributed
around the world (Waters et al., 2018). They can be resolved using
ultra-high precision radiometric dating, with laminated deposits potentially
offering a year-by-year and even seasonal record of environmental
change (Zalasiewicz et al., 2019b). Deposits may contain artifacts and
can sometimes be tied to specific historical events (Hoffmann and
Reicherter, 2014; Zalasiewicz et al., 2019a). Many of these stratigraphic
signals will persist long into the future. The Anthropocene represents
the overlap of geological, historical and instrumental time, its depos-
its capturing a rich, expansive and growing archive of our planet
during a time of transformation.
The Anthropocene as a term, while lacking a long tradition, has
rapidly gained extraordinary currency within the Earth Sciences and
indeed throughout the sciences, social sciences and humanities (Zala-
siewicz et al., 2021). As with the Holocene subdivisional terms, for-
malization of the Anthropocene will increase its utility and reduce
confusion, at least within geology and cognate disciplines (Head, 2019).
And as with the Meghalayan Stage, formalization will provide an iso-
chronous base complementing the many diachronous time scales that
already chart both human cultural activities and natural environmen-
tal changes.
Acknowledgements
We th an k t he Ma x Pl anc k In sti tu te fo r Ch em ist ry, M ain z, wh er e th e
late Paul Crutzen worked for many years, for elucidating Nielsen’s
(2021a) comment that Crutzen had endorsed the results of his work.
Prof. Crutzen clarified that he did notice and acknowledge but did not
review or endorse the paper ‘The Great Deceleration and proposed
alternative interpretation’. MJH acknowledges support from a Natu-
ral Sciences and Engineering Research Council of Canada Discovery
Grant. Simon Turner kindly supplied Figure 11. This article has bene-
fitted from stimulating ongoing discussions with colleagues in the
Anthropocene Working Group. We are most grateful to two anony-
mous reviewers for their insightful comments and to Brian Marker as
Associate Editor for helpful guidance.
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Martin J. Head is a stratigrapher and Pro-
fessor of Earth Sciences at Brock University,
Canada, and is a status-only full professor at
the University of Toronto, Canada. He is cur-
rently Vice-Chair of the International Sub-
commission on Quaternary Stratigraphy (SQS ),
having served as its Chair (2012–2020), and
is Co-Convener of its Working Group on the
Middle–Upper Pleistocene Subseries Boundary.
He is concurrently a voting member of the
SQS Working Group on the Anthropocene
and of the International Subcommission on
Stratigraphic Classification, and an ad visory
board member of the INQUA Stratigraphy
and Chronology Commission (SACCOM).
David Fagerlind is a PhD student in Sus-
tainability Science at the Stockholm Resil-
ience Centre, Stockholm University, Sweden.
His research spans a wide range of topics
related to how human activities affect the Earth
System, with an emphasis on the potential of
alternative economic models such as green-,
circular- and bio- in contributing to sustain-
able development.
Will Steffen is an Ear th Sys tem sc ienti st. He
is a Councillor on the publicly-funded Cli-
mate Council of Australia that delivers inde-
pendent expert information about climate
change. He is also an Emeritus Professor at
the Australian National University (ANU),
Canberra; a Senior Fellow at the Stockholm
Resilience Centre, Sweden; and a member
of the Anthropocene Working Group. From
1998 to mid-2004, Steffen was Executive
Director of the International Geosphere-Bio-
sphe re Programme, ba sed in St ockho lm. His
research interests span a broad range within
Earth System science, with an emphasis on
sustainability and climate change.
