Extraordinary human energy consumption and resultant geological impacts beginning around 1950 CE initiated the proposed Anthropocene Epoch

Growth in fundamental drivers—energy use, economic productivity and population—can provide quantitative indications of the proposed boundary between the Holocene Epoch and the Anthropocene. Human energy expenditure in the Anthropocene, ~22 zetajoules (ZJ), exceeds that across the prior 11,700 years of the Holocene (~14.6 ZJ), largely through combustion of fossil fuels. The global warming effect during the Anthropocene is more than an order of magnitude greater still. Global human population, their productivity and energy consumption, and most changes impacting the global environment, are highly correlated. This extraordinary outburst of consumption and productivity demonstrates how the Earth System has departed from its Holocene state since ~1950 CE, forcing abrupt physical, chemical and biological changes to the Earth’s stratigraphic record that can be used to justify the proposal for naming a new epoch—the Anthropocene. Human energy consumption and productivity have steeply risen around 1950 CE, leading to a departure from the Earth’s Holocene state into the Anthropocene, suggests a quantitative analysis of humanity’s influence on the Earth system.

ky), Northgrippian (8.2 to 4.3 ky), and Meghalayan (4.3 to 0 ky). Here, we trace the human footprint through each Holocene age, with focus on two historical and informal intervals: Pre-Industrial (1670-1850 CE) and Industrial (1850( -1950, within the Meghalayan Age. The Anthropocene as a potential epoch 7,8 is first compared to these earlier Holocene ages, using the human population and its energy consumption and economic productivity, and then assessed by evaluating how human action has disturbed the landscape, altered river discharge (water, particulate and dissolved constituents), and has shifted climate, biogeochemical cycles, biodiversity, and other parts of the Earth System. These changes have already resulted in a sharp distinction in the stratigraphic record between the Holocene and Anthropocene 1,7,8 . This study formulates a consistent quantitative approach evaluating key Earth-surface parameters and their human drivers to validate the contention that the Anthropocene is an epoch-level planetary interval in Earth's history, comparable to or exceeding in planetary impact the Holocene Epoch, and greatly exceeding component Holocene ages.
The Anthropocene Epoch is used here as a geological time unit for potential inclusion in the Geological Time Scale. A proposal to formalize the Anthropocene for this purpose is currently being developed by the Anthropocene Working Group (AWG), which includes many authors of this paper, and will require a defining Global Boundary Stratotype Section and Point (GSSP) to be selected and approved, consistent with ICS standard practice.
A Holocene history of the human footprint The Greenlandian Age (11.7 to 8.2 ky) constitutes the first 3464-y of the Holocene, driven by Milankovitch warming of~+0.5°C 9 , during which the Inter-Tropical Convergence Zone shifted northward 10 and Northern Hemisphere ice sheets ablated. Atmospheric CO 2 and CH 4 concentrations continued a trend of rapid rise initiated in the latest Pleistocene and peaking at~10 ky 11 . Coastal human populations retreated inland from initial settlements 12 , especially on deltas 13 , as global mean sea level rosẽ 48.5 m, at a rate of~15 mm/y between 11.4 ky and 8.2 ky 14 .
Regional extinctions of large terrestrial mammals (e.g., ground sloths in North and South America) correlate with the arrival of humans 15 . Humans lived as foragers, fishers, or hunters, but in a few locations began to cultivate domesticated food crops 16 . Energy sources were wood-burning and human muscle, and more rarely, animal muscle, with an estimated per capita energy consumption of 6.2 GJ/y, ranging from 5.8 to 6.5 GJ/y (Fig. 1b, Table 1). The human population during the Greenlandian consumed 0.12 zetajoules of energy (with 1 ZJ = 10 21 J). Global productivity is used here as a measure of output per unit of input, such as labor, capital or any other resource calculated for the global economy (GDP per capita per unit time), and if meaningful at all for the Greenlandian, was very low (Fig. 1c, Table 1). During the Northgrippian Age (8.2 to 4.3 ky), global mean sea level rose another~14.5 m, mostly in the first 1500-y, as the great Northern Hemisphere ice sheets largely had disappeared by 7000y ago 14,17 . The Age-averaged rate of global mean sea-level rise was~3.6 mm/y ( Table 1). Global climate was relatively stable at a temperature plateau until 5.48 ky, when the planet cooled −0.2°C, but with regional exceptions 9 . The trend in atmospheric CO 2 and CH 4 concentrations changed from slightly falling to slightly rising, at~8 ky and~5 ky respectively. Although some have argued that this increase reflected deforestation in response to expanding agriculture, in particular rice cultivation in the case of methane 10 , others suggest that the rise reflects the gradual adjustment of ocean chemistry towards an equilibrium state following deglaciation 18 . Some humans, still a minority at the end of the Northgrippian Age, organized into structured agrarian societies. Once sea level stabilized, the human population grew to 27 M (0.03%/y), as urban centers and ports developed (Fig. 1a 19,20 ). Energy sources included wood burning, human and animal muscle, with the per capita energy consumption at 7.1 GJ/y, ranging from 6.5 to 7.8 GJ/y (Fig. 1b, Table 1). Humans expended 0.34 ZJ across the Northgrippian Age, a 332% increase from the Greenlandian, reflecting an increased human population. Human productivity remained low (Fig. 1c, Table 1). The anthropogenic footprint included regional soil erosion from deforestation, a proliferation of pastureland, and some mining 21,22 . Extinction of large terrestrial mammals correlates with climate change 23 , though some extinctions have been linked to human actions 15 .
The Meghalayan Age, as represented here, is the recent 4.2-ky interval (to~1950 CE), when global mean sea level rose 1.0 to 1.5 m, or~0.3 mm/y 14 , as the global climate cooled −0.5°C 9 , in what is referred to as Neoglaciation 24 . Insolation decreased, and there were slight rises in atmospheric CO 2 and CH 4 concentrations 25 . Human populations increased by an average 0.2%/y, reaching a population of 2500 M by 1950 CE (Fig. 1a, Table 1). Apparently related to sea-level stabilization, biological productivity on the coastal margin increased dramatically and likely initiated the further movement to large empire level organization in human society facilitating greater demand for goods, increased trade and complex urbanization 19,20,26 . Large-scale water diversion schemes were built, and extensive farming practices increased 21,27 . Coal became a common energy supply in the 19 th century 28 . Per capita energy consumption averaged 8.3 GJ/y, ranging from 7.8 to 40 GJ/y, with humans expending 14.2 ZJ across the Meghalayan Age, a 24-fold increase over the Northgrippian Age (Fig. 1b, Table 1). Per capita GDP averaged $144/y (Fig. 1c, Table 1). Humans transferred plant and animal species beyond their native ranges, exemplified by the spread of chickens 29 , maize 30 and Pacific rats 31 . Human impacts produced extensive regional losses 32  Below we discuss two informal intervals, the Pre-industrial and the Industrial, that capture the end of the Meghalayan.
Pre-Industrial interval (1670-1850 CE). A 180 y-long interval when Holocene sea-level rise was at its slowest~0.15 mm/y 14 , with no discernible trend during the 18 th century, and a slight fall from 1800 to 1850 CE 39 , when Alpine glaciers were at their maximum Meghalayan extent 40 in response to extensive volcanism 41 . Earth had no discernible climate trend~0.0°C 9 during this interval, with cooling pulses varying regionally 42 . Human population expanded from~600 M to 1247 M, a growth rate of 0.4%/y (Fig. 2a). The per-capita energy consumption was 18.4 GJ/ y, ranging from 13.5 to 22 GJ/y (Fig. 2b, Table 1), with humans expending 2.9 ZJ or 20% of the human energy consumption during the 4,200-y Meghalayan Age (Table 1). Novel energy sources included whale oil 43 and stream energy; for example, there were >65,000 water-powered mills in the U.S.A. prior to 1840 CE 44,45 . Human-enabled species introductions expanded, and transfers happened rapidly, exemplified by the spread of accidentally introduced aquatic mollusks in Europe 46 . This informal interval represents the fundamental transformation from pre-industrial to full industrial energy use. Prior to 1670 CE, expenditures in England used to obtain basic energy resources (human food, fodder for animals, and wood fuel) amounted to 50-70% of GDP 47 . By 1850 CE, with the growing use of coal, less than 30% of GDP was allocated to obtaining energy, and <10% after 1950 CE, as fossil fuels dominated energy use 47 . Global per capita GDP increased by 1750 CE to $178/y in 1990 international dollars ( Table 1, Fig. 2c).
Industrial interval (1850( -1950. This 100-y interval captures the change in human-nature interactions 48 . Atmospheric CO 2 increased from the spread of industrial activity and drove a planetary warming by~+0.2°C 49 (~+ 0.6 W/m 2 ) 49 , on an otherwise essentially flat Milankovitch insolation signal 50,51 . Solar variability had very little effect, with the number of sunspots rising in 1950 CE to levels slightly lower than that in the 1860s and the 1780s 52,53 , in contrast to the pre-industrial Maunder Minimum from 1645 to 1715 CE 54 . Thus, natural variability contributed little to warming, (<0.2 W/m 2 ) 49 during this interval, where the main natural changes were brief intervals of cooling related to large volcanic eruptions that ejected reflective material into the stratosphere (e.g. Krakatoa in 1883 CE) 55,56 . Sea-level rise accelerated to~0.5 mm/y in the late 1800s, and to~2.2 mm/y by 1940 CE, before beginning a temporary deceleration 57 . This pattern is consistent with the natural fluctuations in the warmth of the North Atlantic in responses to changes in the Atlantic Meridional Ocean Circulation that induces regional and slight global warming as it accelerates, reversing as it decelerates 58 .
Human population grew at 0.8%/y, from 1250 M to 2500 M (Figs. 1a, 2b, Table 1). Energy consumption per capita averaged 27.2 GJ/y, ranging from 22 to 40 GJ/y (Fig. 2b), accounting for 4.9 ZJ or 35% of the energy consumption across just 2.4% of the 4200-y Meghalayan Age (Table 1). In addition to the growing use of coal, new energy sources included hydroelectric power, oil and natural gas, more than offsetting declines in whale oil and stream power (driven by gravity). Many large rivers were engineered, with levees, dams and water diversion schemes 59 . Some lake 60 and marine 61 ecosystems started to turn hypoxic. Biodiversity loss increased and introduced species, such as the giant African snail and naval shipworm 62,63 , spread through terrestrial and aquatic environments 21,32,64 . Dispersals were facilitated by increasing global trade 65 . Per capita GDP had increased by 1900 CE to $679/y in 1990 international dollars ( Table 1, Fig. 2c), underwriting new global transportation systems and power sources.
Although the European industrial interval began in the 1700s, we use 1850 CE as the start of the interval, given the remarkable change in both global energy use and global productivity (Fig. 2c). For most of the Holocene Epoch, human productivity (GDP per capita: see SOM Historical GDP Consumption Data) increased linearly with a growing population (Fig. 2c). From 1850 CE onwards, human productivity accelerated (Fig. 2c), which explains why that time period was originally suggested as the start of the Anthropocene 66,67 . For most of the Holocene, the ratio of human productivity to energy use decreased (Fig. 2d). After 1850 CE, human society became more productive per unit of energy use (Fig. 2d). During the 11.7 ky of the Holocene Epoch, including the Industrial interval, the global human population consumed 14.6 ZJ of energy of which 35% was consumed in the final 100 years.  70 , during an interval of limited sunspot influence and a flat Milankovitch signal. Sunspot numbers rose slightly from their 1950 CE levels to peak levels in 1980 CE and 1990 CE that are more or less similar to those reached in the 1780s and the 1860s, and then began declining 52 even as warming continues (Box 1).
Atmospheric CO 2 levels reached 415 ppm in 2019 71 , higher than at any time in the past 3 million years 71 . Planetary response to this atmospheric warming includes: • Sea-ice volume shrinkage: 300 ± 100 km 3 /y loss (~275 Gt/y) in the Arctic Ocean since 1980 CE 72 [80][81][82] , threatening the survival of particularly soluble organisms, such as aragonitic pteropods. Increasing acidity may raise the calcium carbonate compensation depth (CCD) in the deep ocean, causing the demise of carbonate-shelled deep-water benthic organisms.
Since 1950 CE, the human population has rapidly increased, with societal and medical advances extending lifespans. Industrial-scale agriculture, with its global distribution system, presently feeds a global population of 7800 M that grows at an average rate of 1.63%/y, presently 71 M/y. In absolute numbers, human migration within and between continents has reached its historical zenith during the Anthropocene, as many coastal cities have transformed into megacities (>10 M) in just decades 83 ( Table 2).
1950 CE also marks an important upturn in the global spread of technological knowledge occurring when societies became more economically interdependent (the Great Acceleration 48,84 ). Between 1650 and 1750 CE, the annual citations of scholarly references grew at~0.15%/y 85 , increasing by an order-ofmagnitude to~1.5%/y during 1750-1927 CE. After 1927 CE for all subjects, and after 1947 CE for the natural sciences, citation rates have jumped to~8%/y 85 following compulsory education and widespread literacy.
Global per capita GDP has risen rapidly in the Anthropocene, to a current figure of $12,500/y (Fig. 2, Table 2). This inflationadjusted global productivity is an order-of-magnitude greater than during the Industrial interval just 70 years earlier (Tables 1, 2, Fig. 2c). Since 1950 CE, energy consumption by humanity has averaged 61 GJ/y per capita (range 40 to 75 GJ/y; Fig. 2b, Table 1), enabled by a diversified portfolio of energy sources (coal, oil, gas, nuclear, and renewables). Fossil fuels power more than 80% of the economy 86 . In total, 60% of all human-produced energy has been consumed since 1950 CE, at 22 ZJ, more than in the entire previous Holocene (~14.6 ZJ: Table 1). Since 1871 CE, the Earth's oceans have stored~436 ZJ of solar energy trapped through the increases in anthropogenic greenhouse gases 87 , and from warminginduced increases in water vapor 88 , a reinforcing feedback. This is more energy by an order-of-magnitude than associated with direct human production and consumption (at 23.3 ZJ since 1871 CE). Approximately half of the Anthropocene sea-level rise stems directly from this steric effect on ocean volume, with the remainder largely derived from the melt of terrestrial snow and ice 49 . Since about 1950 CE, the global ocean has progressively warmed both at the surface and increasingly to depths exceeding 2000 m. Heat is transferred vertically by storms and eddies, and by the sinking of surface water made dense by cooling, especially in the Labrador and Norwegian-Greenland seas in the Atlantic and in the Southern Ocean around Antarctica. Many anthropogenic impacts post-1950 CE are planetary, with greater than regional significance, and scale up with the population of humans and their energy consumption and economic productivity 48 . Below we offer 16 examples relevant to, and in support of, this Anthropocene Epoch thesis: 1. The magnitude of the anthropogenic N cycle is roughly equivalent to the global natural N cycle 89,90 . However, such a simplified numerical comparison underestimates the ecological consequences of such a perturbation which includes impacts on climate change, water and air quality, ozone depletion, and biodiversity loss [91][92][93] . Globally, reactive nitrogen (N r ) increased by~50%, between 1600 and 1990 CE, with atmospheric emissions of N r increasing by 250%, and N r deposition into marine and terrestrial ecosystems increasing by more than 200% 94,95 (Table 2). More than half of human population is alive today because of the production and use of N r in fertilizers 96 114 . There is now concern that the increasing demand for sand for building megacities is outstripping supply. Offshore dredging for aggregates destroys marine habitats, as does bottom trawling for fish and shellfish, affecting marine biodiversity. Since industrialization, human mining activities have impacted the global mobilization of naturally occurring elements, particularly the cycles of the chalcophile elements (e.g., As, Cd, Cu- Fig. 3e, Hg, Ni, Pb, Sb, Zn) associated with the smelting and refining of base metal ores, coal combustion and cement production 115,116 . In recent decades, platinum group elements that are required for advanced materials and technologies have been profoundly affected [117][118][119] . Increased extraction rates of ores (Table 2) have caused a transfer of metals from the lithosphere to these metal-in-use products and thence to wastes 120 . While negligible amounts of the industrial metals were extracted and put into use before 1900 CE 121 Table 2 for data, and Table 2  Pb, Hg, Se and Sn geochemical cycles now reach a global scale 123 , with increasing perturbations for other metals 124 . 5. Industrial-scale agriculture accounts for 50% of terrestrial soil loss 125,126 , leaving nearby rivers with increased sediment and nutrient loads [126][127][128] . Forest clearing for the creation of agricultural lands has long increased soil erosion rates 27,129 , but contemporary rates of soil loss from cropland exceed the natural rates of erosion 30-fold 130 . Cropland represents 11% of the global land area, but accounts for~50% of soil erosion 131 ; soil erosion rates from forests are 77 times lower. From 2001 to 2012 CE, when 2.3 Mkm 2 of forest was lost, only 4% of this loss was converted to cropland, but was responsible for more than half of the increase in soil erosion 132 . Remaining soils are then progressively compacted by large agricultural machines and have their organic content gradually reduced, requiring replacement with artificial fertilizers (Fig. 3f). Soils have also become increasingly dry in response to atmospheric warming 133 . The industrial agricultural system consumes~10 units of energy for each unit of food energy produced 134 143 ; the result has been a major increase in carbonaceous fly-ash in natural archives across the world since the 1950s 144 . 7. Coastal engineering has globally added thousands of km of groins, jetties, seawalls, breakwaters and harbors to control the movement of coastal sediment, leading either to coastal erosion or to siltation 58,145 . Lacking the delivery of silt from the interior, along with the rise of coastal aquaculture and coastal megacities (Table 2), river deltas are subsiding at rates of tens to hundreds of mm/y [146][147][148] . Many coastlines now retreat at highly variable rates of tens to hundreds of m/y 145 , except where substantial seawalls are emplaced, as in the Netherlands. The global extent of wetlands today is 10 Mkm 2 149 . Best estimates suggest that 54-57% of the total area of natural wetlands has already been lost, with the rate of loss accelerating during the 20 th and 21 st centuries 150 . In many tropical areas, natural and protective mangrove swamps have been replaced with shrimp and fish farms, further exposing coastlines to erosion 145 . Consequences of this wetland loss include the oxidation of extensive reserves of organic matter into CO 2 , reduced water retention and storage, more groundwater infiltration by saltwater, and loss of wildlife habitat and biodiversity. 8. Plastic production has increased from~2 Mt/y in the 1950s, to 359 Mt/y in 2018 CE [151][152][153] , including 526 B/y of plastic beverage bottles and 3000 B/y of plastic cigarette filters 154 (Fig. 3c, Table 2). Plastic debris now enters into the ocean at rates between 4.8 and 12.7 Mt/y 155 , and microplastics are increasingly being transported by aeolian vectors, permitting true global distribution, even to Arctic snowfields 156 , forming a near-ubiquitous and unambiguous marker of Anthropocene strata 8 . 9. Human-mediated mineral species and synthetic minerallike compounds now exceed 180,000 in number, with most species created since 1950 CE 8,157 (Table 2). Earth's geological processes over the last 4.5 By have only supported the formation of 5,300 naturally occurring mineral species, including those mediated by biological processes 157,158 . 10. Concrete production in modern times began in 1824 CE, with the patenting of the Portland Cement recipe. Production remained minor until 1950 CE when 0.13 Gt/ y of cement produced~1 Gt/y of concrete. Today, global cement and concrete production are 4 Gt/y and 27 Gt/y, respectively (Fig. 3d, Table 2), incorporating novel geochemical and mineralogical compositions, such as organic polymer fibers, silica fume, fly ash, nanotubes and nanospherules of silica, iron, graphene and titanium oxide 159 . Cement production requires the heating of CaCO 3 to release CO 2 , leaving lime in the form of calcium oxide (CaO) or hydroxide. 11. As the planet heats up, water vapor evaporated from the oceans, lakes, reservoirs and soils has become the dominant greenhouse gas accounting for ∼50% of the greenhouse effect, followed by clouds (∼25%), CO 2 (∼20%), then CH 4 and N 2 O 88 . Atmospheric carbon dioxide is, however, the main driver of planetary warming. In 1750 CE, humans produced 0.009 Gt/y of atmospheric CO 2 , increasing to 0.2 Gt/y by 1850 CE, 5.3 Gt/y by 1950 CE, then accelerating to 36.1 Gt/y by 2017 CE 160 (Fig. 3b, Table 2). Emission sources include combustion of coal, oil, and gas, and cement production. Similarly, atmospheric methane globally increased from 719 ppb in 1750 CE, to 1162 ppb in 1950 CE, and 1850 ppb in 2017 CE 160 ; atmospheric nitrous oxide concentration shows a similarly increasing trend 160 (  163 . Wild bird and mammal totals today have a much-reduced biomass~0.009 Gt C 163 . For comparison, the total biomass of modern human-cultivated crops is ≈10 Gt C 163 . It is estimated that Earth's current total vegetation biomass is half of potential biomass stocks prior to human perturbation, mainly through forest loss 163,165 . 14. Anthropogenic emissions of sulfur-containing gases exceed natural fluxes by 2 to 3 times 166 . Presently there is a peak in atmosphere emissions of SO 2 (~100 Mt/y), although emissions are expected to decline 167 . Emissions of SO 2 from nickel smelting in Sudbury, Ontario, reached their zenith in the 1960s (2.5 Mt/y), but technological innovations have since lowered these by~95% 168 . Phosphorus mobilization by human activities currently exceeds the natural global cycle by a factor of 3 169 . Like N, P is commonly growth-limiting for biota with profound ecological consequences 170,171 , with both nutrients contributing to surface water eutrophication. 15. The annual rate of species invasions has greatly increased since the late-20 th century 172 . Species inventories of ecosystems record rapid or substantial changes in many seas 173 , rivers 174 , estuaries 175 183 . Due to its long persistence (half-life 24,110 y), this naturally rare radionuclide will be detectable for~100 ky into the future 184 .
Human population has exceeded historical natural limits, with 1) the development of new energy sources, 2) technological developments in aid of productivity, education and health, and 3) an unchallenged position on top of food webs. Humans remain Earth's only species to employ technology so as to change the sources, uses, and distribution of energy forms, including the release of geologically trapped energy (i.e. coal, petroleum, uranium). In total, humans have altered nature at the planetary scale, given modern levels of human-contributed aerosols and gases 88,160 , the global distribution of radionuclides, organic pollutants and mercury 123,139,141,144 , and ecosystem disturbances of terrestrial 185,186 and marine environments 187 . Approximately 17,000 monitored populations of 4005 vertebrate species have suffered a 60% decline between 1970 and 2014 CE 188 , and~1 million species face extinction, many within decades 189 . Humans' extensive 'technosphere', now reaches~30 Tt, including waste products from non-renewable resources 190 .
Such vast alterations to Earth's natural atmospheric, hydrologic, pedologic, biologic, biogeochemical and sedimentary systems not only have changed the Earth System considerably [191][192][193] but have also created innumerable globally detectable and preservable signals. These changes are now being used to justify a new geochronologic epoch, the Anthropocene 1,194 .
A thought experiment in measuring human impact Humans, like all living organisms, inject a biological force into their environment. Individualized, this human force should collectively scale up with a growing population. With that logic and other things held constant, one billion humans would offer 1000 times the environment force of one million people. Early humans with their limited numbers (Fig. 1a), had a recognizable but minimal impact on the planet's terrestrial and marine environments through most of the Holocene (Table 1). Population grew slowly (Table 1, Supplementary-Table 1), and energy use remained low (Figs. 1b, 2b) even with the advances of toolbased hunting, use of fire, employment of animals in agriculture or travel, and the development of settlements. Earth's surface environment also has some ability to repair itself, such that 1000 humans across 1000 y would likely have a smaller lasting environmental impact than one million humans in just one year. The time-averaged human population in the Holocene is 97 M, compared with the Anthropocene's population of 4940 M (Supplementary- Table 1). Using a constant per capita energy consumption of say 1 GJ/y, human-derived energy use during the Holocene (to 1950 CE) would be 1.13 ZJ (97.2 M × 11,630 y × 1 GJ/y), and just 0.35 ZJ in the Anthropocene, a longer Holocene duration being more important than a larger Anthropocene population. However, per capita energy consumption increased by an order-of-magnitude across 11,700 years ( Table 1, Fig. 1b). As a consequence, humans have already consumed more energy in the short space of the Anthropocene than in the entire Holocene (21.7 ZJ versus 14.6 ZJ).
Humans became a geological force over the last 300 y, particularly after the start of the global industrial revolution in 1850 CE when excess energy (fossil fuel) became widely available. There are strong relationships amongst three parameters: global population, global energy use, and global productivity ( Table 2, Figs. 2 and 4). Increases in human productivity support larger populations that consume higher levels of energy and materials that in turn support increases in productivity. The harnessing of fossil fuels has allowed humans to apply this excess in available energy beyond simple food production and survival. As a result, the growth rate in human population increased rapidly, peaking during the mid-20 th century (Fig. 2a), as did the associated rates of energy consumption and productivity ( Figs. 1 and 2d, Tables 1 and 2). The result has been the mid-20 th century 'Great Acceleration' when humanity began to dominate many of the planetary cycles as outlined above. Like the intertwining of global human population, energy consumption and productivity, major environmental tracers also appear tightly coupled to each other and to these three human forces (Table 2, Figs. 3 and 4). It should be of no surprise then that the global reservoir capacity of large dams, or atmospheric CO 2 , each track closely with global energy use ( Fig. 3a, b, Table 2), or that global plastic or cement production closely follows economic productivity (Fig. 3c, d, Table 2), or that the global production of ammonia (NH 3 ) and copper correlate highly with global human population (Fig. 3e, f, Table 2), as with many other human environmental signals outlined in Table 2: shrimp farming, production of gypsum, salt, iron, steel, sulfur, helium, aluminum, mineral species, atmospheric gases (CO 2 , N 2 O, CH 4 ), terrestrial freshwater budgets, surface temperatures, and sea levels. These major environmental parameters have been strongly altered by the mid-20 th century (and beyond, Table 2).
The environmental parameters discussed above should be understood as the societal forcings that lead to stratigraphic markers that will characterize the Anthropocene, such as horizons identified by extinctions or invasive species, radioisotopes, elevated natural and novel chemical compounds, etc. In and of themselves, the societal metrics that we have identified here may not define the Anthropocene, but they can lead to the markers that do and, if present trends continue, will.
Proposed Anthropocene versus Holocene epochs The Holocene Epoch, the most recent of the Quaternary interglacials, was a time of warm, relatively stable (±0.5°C) climate that fluctuated in response to variations in Earth's natural systems (e.g., Milankovitch): ice sheet volume decreased, and sea levels rose at an Epoch-averaged rate of 5.54 mm/y, larger than for the proposed Anthropocene Epoch (although if warming continues modern rates will quickly rise). The proposed Anthropocene Epoch sees many other key Earthsurface parameters change in response to human action ( Table 2). Parameters with 200% to 300% variances or larger, compared to the Holocene Epoch, include atmospheric and ocean temperatures, atmospheric CO 2 , CH 4 , and N 2 O levels, global reactive nitrogen, environmental mercury and many other metals, phosphorus release 194,195 , sediment transport, terrestrial soil loss, and terrestrial and marine biomass losses. Parameters with order-of-magnitude increases, compared to the Holocene Epoch, include anthropogenic CO 2 emission rates, human-produced energy, upstream sequestration of sediment, number of "mineral" species, concrete production, rates of species extinction 32 , declines in river runoff, and increased coastal hypoxia. There are also phenomenological changes without precedent in the Holocene, including a warmer and more acidic global ocean, global dispersal of new materials (plastics, ceramics, aluminum metal, radioisotopes, persistent organic pollutants, pharmaceutical compounds, fly-ash particles), and modern alterations to the biodiversity of marine and terrestrial ecosystems, with a globally distributed invasive species component 172 and a greatly raised rate of species extinction 33 . Even Earth's crustal process, such as earthquakes, can now have an anthropogenic imprint 196 .
The Anthropocene Working Group (AWG) has voted to affirm a) the Anthropocene be treated as a formal chronostratigraphic unit defined by a GSSP, and b) the primary guide for the base of the Anthropocene be one of the stratigraphic signals around the mid-twentieth century of the Common Era 1,7,68 . Geological records characterizing the base of the Anthropocene are being assembled, and in due course the Group's recommendations will require approval by the International Commission on Stratigraphy. The narrative and quantitative data presented here strongly underpin the trajectory of the Earth System away from a Holocene state of the system, substantially and globally, around the mid-20 th century, circa 1950 CE 192 . Establishing the proposed new epoch would formalize the use of the term Anthropocene, which already has been used widely in research describing changes induced by human actions and recorded in geological archives.

Data availability
The datasets analyzed during the current study are provided as tables within the main paper or within the accompanying online material file, along with the original data references to peer-reviewed sources including persistent government web links.