¿Se ha cancelado el Antropoceno? por Ian Angus

 

¿Se ha cancelado el Antropoceno?

por Ian Angus

Ian Angus es editor de la revista ecosocialista en línea Climate & Capitalism y miembro fundador de la Red Ecosocialista Global. Es autor de Frente al Antropoceno: el capitalismo fósil y la crisis del sistema terrestre (2016) y, más recientemente, La guerra contra los comunes: despojo y resistencia en la creación del capitalismo (2023), ambos publicados por Monthly Review Press.

Hace unos 2,8 millones de años, el nivel de dióxido de carbono en la atmósfera de la Tierra disminuyó, desencadenando una Edad de Hielo. Desde entonces, los cambios a largo plazo en la órbita y la inclinación de la Tierra, llamados ciclos de Milankovitch, han producido cambios de temperatura global cada 100.000 años más o menos. En las fases glaciales (frías), las capas de hielo de kilómetros de espesor cubrían la mayor parte del planeta; En períodos interglaciares (cálidos) más cortos, el hielo se retiró hacia los polos. Durante los últimos 11.700 años, hemos vivido en un período interglacial que los geólogos llaman la Época del Holoceno.

En circunstancias normales, los glaciares y los casquetes polares ahora estarían creciendo lentamente. Como muestra una investigación reciente, "si no fuera por los efectos del aumento delCO2, el inicio glacial alcanzaría una tasa máxima en los próximos 11.000 años".1 En lugar del calentamiento global, el futuro de la Tierra sería la congelación global, pero solo en un futuro lejano.

Sin embargo, como sabe cualquiera que sea mínimamente consciente de los problemas ambientales, los glaciares y los casquetes polares del mundo no se están expandiendo; se están reduciendo rápidamente. Entre 1994 y 2017, la Tierra perdió 28 billones de toneladas de hielo, y la tasa de disminución ha aumentado en un 57 por ciento desde la década de 1990.2 Incluso si las emisiones de gases de efecto invernadero se reducen rápidamente, las condiciones que impiden el retorno de las capas de hielo continentales probablemente persistirán durante al menos 50.000 años. Si las emisiones no se detienen, el hielo no volverá hasta dentro de al menos medio millón de años.3

En resumen, como resultado directo de las emisiones de gases de efecto invernadero causadas por la actividad humana, la Edad de Hielo ha sido cancelada.

Esta es una prueba concreta de una de las conclusiones más radicales de la ciencia del siglo XXI: "La tierra ha dejado ahora su época geológica natural, el actual estado interglacial llamado Holoceno. Las actividades humanas se han vuelto tan penetrantes y profundas que rivalizan con las grandes fuerzas de la naturaleza y están empujando a la tierra hacia la terra incognita planetaria".4

Los científicos que llegaron por primera vez a esa conclusión llamaron a la nueva época el Antropoceno. Un volumen abrumador de evidencia muestra que ha comenzado una nueva etapa en la historia del sistema terrestre, caracterizada por cambios importantes en muchos aspectos del mundo natural, que se dirige hacia condiciones en las que los humanos pueden no sobrevivir. Han demostrado que muchos de los cambios más grandes son irreversibles en cualquier escala de tiempo humana. Han fechado el comienzo de esta transformación radical a mediados del siglo XX. También han demostrado que los registros físicos del cambio se pueden ver en los estratos geológicos.

Para cualquier observador razonable, el caso es irrefutable. Sin embargo, algunos científicos prominentes niegan que se haya producido un cambio cualitativo, y una de las organizaciones científicas más grandes del mundo ha votado en contra del reconocimiento formal de la nueva época. La investigación y los debates que llevaron a este resultado perverso ayudan a iluminar los desafíos que enfrentan los científicos y ecosocialistas en nuestro tiempo.

Ciencia del sistema terrestre

Durante las décadas de 1970 y 1980, un número creciente de científicos llegó a la conclusión de que los métodos científicos tradicionales centrados en cuestiones locales o regionales eran insuficientes para comprender los problemas ambientales, que la Tierra en su conjunto había entrado en un período de crisis extrema causada por la actividad humana.

En 1972, por ejemplo, Barbara Ward y René Dubos escribieron que "los dos mundos del hombre, la biosfera de su herencia, la tecnosfera de su creación, están desequilibrados, de hecho potencialmente en un conflicto profundo". La Tierra se enfrentó a "una crisis más repentina, más global, más ineludible y más desconcertante que cualquier otra jamás encontrada por la especie humana y que tomará forma decisiva dentro de la vida de los niños que ya han nacido".5

Varios libros superventas de James Lovelock promovieron lo que él llamó la "hipótesis de Gaia": que la materia viva regula activamente el entorno planetario para garantizar condiciones óptimas que sostengan la vida. Sus puntos de vista fueron rechazados por la mayoría de los científicos, pero su popularidad alentó el estudio del planeta en su conjunto. Algunos científicos todavía usan la palabra Gaia como sinónimo del Sistema Terrestre.6

La NASA formó un Comité de Ciencias del Sistema Terrestre en 1983, declarando que su objetivo era "obtener una comprensión científica de todo el sistema terrestre a escala global describiendo cómo han evolucionado sus componentes y sus interacciones, cómo funcionan y cómo se puede esperar que continúen evolucionando en todas las escalas de tiempo".7 Millones de imágenes de alta resolución de la Tierra obtenidas por los satélites Landsat, lanzados por primera vez en 1972, contribuyeron a ese esfuerzo.

En 1986, el Consejo Internacional de Uniones Científicas aprobó la formación del Programa Internacional de la Geosfera-Biosfera (IGBP) "para describir y comprender los procesos físicos, químicos y biológicos interactivos que regulan el sistema terrestre total, el entorno único que proporciona para la vida, los cambios que están ocurriendo en este sistema y la forma en que están influenciados por las actividades humanas".8

El IGBP comenzó a funcionar en 1990, con una secretaría en Estocolmo y una variedad de grupos de trabajo internacionales que involucraron a miles de científicos. Desde cualquier punto de vista, fue "el programa de cooperación científica internacional más grande, complejo y ambicioso que jamás se haya organizado".9 Durante los siguientes veinticinco años, el trabajo más importante en la ciencia del sistema terrestre se realizó bajo el paraguas del IGBP.

One of the IGBP’s founding statements began: “Mankind today is in an unprecedented position. In the span of a single human generation, the Earth’s life sustaining environment is expected to change more rapidly than it has over any comparable period of human history.”10 That statement proved more insightful than anyone imagined in 1990. In 2000, at a meeting where the various working groups reported on a decade of in-depth research, Nobel Prize-winning atmospheric chemist Paul Crutzen concluded that the accumulated changes had broken through the limits of the present geological epoch. “We’re not in the Holocene anymore,” he declared. “We’re in the Anthropocene!”11

The importance of that insight cannot be overstated. Anthropocene was not just a new word, it was a new reality and a new way of thinking about the crisis of the Earth System. Several leading participants in the development of Earth System Science wrote recently:

ESS [Earth System Science], facilitated by its various tools and approaches, has introduced new concepts and theories that have altered our understanding of the Earth System, particularly the disproportionate role of humanity as a driver of change. The most influential concept is that of the Anthropocene, introduced by PJ Crutzen to describe the new geological epoch in which humans are the primary determinants of biospheric and climatic change. The Anthropocene has become an exceptionally powerful unifying concept that places climate change, biodiversity loss, pollution and other environmental issues, as well as social issues such as high consumption, growing inequalities and urbanization, within the same framework. Importantly, the Anthropocene is building the foundation for a deeper integration of the natural sciences, social sciences and humanities, and contributing to the development of sustainability science through research on the origins of the Anthropocene and its potential future trajectories. 12

Crutzen initially suggested that the Anthropocene may have begun with the Industrial Revolution in the 1700s, but subsequent research focused attention on the middle of the twentieth century.

Key to this understanding was the discovery of a sharp upturn in a multitude of global socioeconomic indicators and Earth System trends at that time; a phenomenon termed the “Great Acceleration.” It coincides with massive increases in global human-consumed energy and shows the Earth System now on a trajectory far exceeding the earlier variability of the Holocene Epoch, and in some respects the entire Quaternary Period.13

In 2004, the IGBP published Global Change and the Earth System: A Planet Under Pressure, which synthesized the results of their research on global change and argued that “the Earth System is now in a no-analogue situation, best referred to as a new era in the geological history of earth, the Anthropocene.”14

After outlining what IGBP researchers had learned about the complex dynamics of the Earth System, the authors described how human activities are now changing it in fundamental ways. Their account included the famous “Great Acceleration” graphs, showing the unprecedented increases in economic activity and environmental destruction that began about 1950. The great metabolic cycles that support life on Earth—carbon, nitrogen, water, and more—were disrupted, and “the most rapid and pervasive shift in the human-environment relationship began.… Over the past 50 years, humans have changed the world’s ecosystems more rapidly and extensively than in any other comparable period in human history.”15

A New Reign of Climate Chaos?

Chart 1, adapted from a study of ice-core data by scientists at the Potsdam Institute for Climate Impact Research, shows the average annual temperature in Greenland over the past 100,000 years.16 The first 90 percent of this time was the end of the Pleistocene, a 2.6 million year-long epoch characterized by repeated glacial advances and retreats. In this period, the global climate was not only cold, it was in general extremely variable.

Modern humans walked the earth for all the time shown in this graph, but until the Holocene they lived in small, nomadic groups of hunter-gatherers. Climate historian William J. Burroughs, who calls the time before the Holocene the “reign of chaos,” compellingly argues that so long as rapid and chaotic climate change continued, agriculture and settled life were impossible. To succeed, agriculture needs not just warm seasons, but a stable and predictable climate—and indeed, not long after the Holocene began, humans on five continents independently took up farming as their permanent way of life. “Once the climate had settled down into a form that is in many ways recognizable today, all the trappings of our subsequent development (agriculture, cities, trade, etc.) were able to flourish.”17

The Holocene has been one of the longest stable warm periods in the last half a million years.18 From 11,700 years ago to the twentieth century, the average global temperature did not vary by more than one degree Celsius—up or down half a degree. That is not to say that Holocene weather was without extremes: the one-degree average variation included droughts, famines, heat waves, cold snaps, and intense storms. But overall, it was marked by a not-too hot, not-too cold, “Goldilocks” climate.

Chart 1. Average Annual Greenland Temperature, 100,000 Years Ago to Present

Notes and Sources: Temperature record of the past 100,000 years showing dramatic swings between cold (glacial) and warm periods followed by the warmer Holocene Epoch, starting approximately 11,700 years ago. Andrey Ganopolski and Stefan Rahmstorf, “Rapid Changes of Glacial Climate Simulated in a Coupled Climate Model,” Nature 409, no. 6817 (January 2001): 153–58.

In 2009, twenty-nine leading Earth System scientists defined nine planetary boundaries that, if crossed, could destabilize the Earth System. Staying within the boundaries would maintain Holocene-like conditions, the only environment that we know for sure can support large and complex human societies. The most recent update, published in 2023, found that six of the nine boundaries have been crossed. The Earth System has left the safe operating space for climate change, biosphere integrity, land system change, freshwater change, biogeochemical (nitrogen and phosphorus) flows, and novel entities, and it is close to the boundary for ocean acidification. These shifts portend a climate that is hotter, more variable, and less predictable than any settled human society has experienced—a new reign of chaos.

Rarely has a new scientific concept won wide support as quickly as the Anthropocene. The decade following Crutzen’s spontaneous declaration produced a large body of Earth System research exploring aspects of the concept. An inflection point occurred in 2012, when the IGBP and other Earth System science organizations held a conference on global change in London. More than three thousand people attended in person and three thousand more attended online. The meeting’s final declaration was unequivocal:

Research now demonstrates that the continued functioning of the Earth system as it has supported the well-being of human civilization in recent centuries is at risk. Without urgent action, we could face threats to water, food, biodiversity and other critical resources: these threats risk intensifying economic, ecological and social crises, creating the potential for a humanitarian emergency on a global scale….

Humanity’s impact on the Earth system has become comparable to planetary-scale geological processes such as ice ages. Consensus is growing that we have driven the planet into a new epoch, the Anthropocene, in which many Earth-system processes and the living fabric of ecosystems are now dominated by human activities. That the Earth has experienced large-scale, abrupt changes in the past indicates that it could experience similar changes in the future. This recognition has led researchers to take the first step to identify planetary and regional thresholds and boundaries that, if crossed, could generate unacceptable environmental and social change.19

But Geology…

Still, something was missing. “Holocene” is a geological term: it names the last 11,700 years, the most recent stage in the planet’s geological history. It is an epoch in the Geological Time Scale, which was created to ensure that all geologists have a common understanding of the stages of Earth’s physical history and use the same terms to describe it. Any change to the Geological Time Scale must be formally approved by the International Commission on Stratigraphy (ICS) and the International Union of Geological Sciences (IUGS), both of which are notoriously conservative and resistant to change.

It was not until 2009 that the ICS asked palaeobiologist Jan Zalasiewicz of the United Kingdom’s Leicester University to chair a working group to investigate and report on whether geologists should formally recognize the Anthropocene as a new epoch.

The Anthropocene Working Group (AWG) had to start from scratch: past working groups could base their deliberations on decades of existing research, but no one had yet looked for geological evidence of a break between the Holocene and a possible new epoch. In the years following the formation of the AWG, geologists around the world conducted dozens of research projects on that subject, with results published in peer-reviewed journals and in books edited by AWG members.

There was an immense amount of data and analysis to assimilate, especially since the group was small and its members were unpaid volunteers. However, by 2015 they had accumulated and evaluated a mass of geological evidence—strong physical indicators that a radical change was taking place. An article summarizing that evidence was published in the journal Science in January 2016.

The appearance of manufactured materials in sediments, including aluminum, plastics, and concrete, coincides with global spikes in fallout radionuclides and particulates from fossil fuel combustion. Carbon, nitrogen, and phosphorus cycles have been substantially modified over the past century. Rates of sea-level rise and the extent of human perturbation of the climate system exceed Late Holocene changes. Biotic changes include species invasions worldwide and accelerating rates of extinction. These combined signals render the Anthropocene stratigraphically distinct from the Holocene and earlier epochs….

The stratigraphic signatures described above are either entirely novel with respect to those found in the Holocene and preexisting epochs or quantitatively outside the range of variation of the proposed Holocene subdivisions. Furthermore, most proximate forcings of these signatures are currently accelerating. These distinctive attributes of the recent geological record support the formalization of the Anthropocene as a stratigraphic entity equivalent to other formally defined geological epochs. The boundary should therefore be placed following the procedures of the International Commission on Stratigraphy.20

By 2023, the AWG had decided, by an overwhelming majority, that a new geological epoch began in about 1950, and that the best stratigraphic signal for the beginning of the new epoch was the presence of plutonium isotopes, created and spread by the atmospheric hydrogen bomb tests that the United States and the Soviet Union conducted between 1952 and 1963.

Twelve locations on five continents were studied in detail for suitability as reference sites. The onset of the Anthropocene could be clearly identified in all twelve, but the researchers selected Crawford Lake in southwestern Ontario as the best location for a “golden spike.” For centuries, unique conditions there have preserved annual layers of sediment, including undisturbed layers containing plutonium. Three other locations, in Japan, China, and Poland, were selected as auxiliary sites.

Opposition

The most common argument against the new epoch was that human beings have always changed the environment, so the Anthropocene is nothing new. Late in the debate, this argument took the form of a proposal that the Anthropocene should be considered as an informal “event,” spread over thousands of years. In that framework, the Great Acceleration was at most an intensification of long-term continuing changes, not a qualitative shift.21

AWG members replied: “the Anthropocene is de facto a new epoch, not an encapsulation of all anthropogenic impacts in Earth history.” Indeed, that idea “runs counter to the Anthropocene’s central meaning” by extending it to all human-induced changes over thousands of years and ignoring “the abrupt human-driven shift a new Earth System state that has exceeded the natural variability of the Holocene.”22

In short, the proposal preserved the word but erased its fundamental meaning and radical content.

Other arguments against formalizing the Anthropocene ranged from trivial (the name is not appropriate; the idea comes from outside geology; other epochs are longer) to insulting (this whole thing is just about getting publicity). In 2017, members of the AWG assembled the published arguments against the Anthropocene and prepared responses to each. The resulting article was polite and collegial but nonetheless devastating. It left the critics with no scientific basis for continued opposition.23

Yet, as Zalasiewicz later wrote: “neither this strengthened evidence base, nor further evidence subsequently gathered, did anything to diminish the outright opposition to the Anthropocene from a minority of AWG members and their colleagues.” He went on:

This suggested that this opposition and that of others in the ICS—the strong opposition of the highly influential ICS Chair, Stanley Finney, was a significant factor—even when responded to and countered was not based on the amount and quality of stratigraphic evidence. Rather, it seemed to reflect more deep-seated aspects of the chronostratigraphically proposed Anthropocene….

Evidence-based refutations did nothing to prevent further reiterations of the “event” suggestion, again suggesting that the body of stratigraphic evidence assembled by the AWG was of little relevance to the central question of whether an Anthropocene epoch should exist at all.…

The Anthropocene clearly touches nerves that more ancient strata do not reach.24

In November 2023, when the AWG submitted its formal proposal to recognize the new epoch, it also submitted a complaint to the Geoethics Commission, charging that the executives of the ICS and the IUGS had deliberately hindered and undermined their work. The Commission reportedly supported the complaint and recommended that no vote be held. The IUGS appears to have ignored the recommendation.

If normal procedures had been followed, the AWG submission should have initiated a period of open discussion. Instead, in March 2024 the AWG’s proposal was abruptly voted down after a brief discussion in a closed-door setting. The IUGS did not reply to the AWG submission, it simply announced its rejection.

We can only speculate about the motives that led to this preposterous decision, but as archaeologists Todd Braje and Jon Erlandson have pointed out, this debate “has the potential to influence public opinions and policies related to critical issues such as climate change, extinctions, modern human-environmental interactions, population growth, and sustainability.”25 In that respect, it is surely relevant that geology—a science deeply implicated in the discovery and exploitation of fossil fuels—has been, shall we say, conservative on the question of climate change.

In 2016, the chair of the ICS charged that “the drive to officially recognize the Anthropocene may, in fact, be political rather than scientific.”26 The opposite seems more likely: opposition to the idea of the Anthropocene is political, not scientific. Certainly, he and his colleagues have ensured that no one can use the prestige of the ICS and IUGS in support of decisive action to prevent climate chaos. The price paid for that political win is a defeat for geology’s credibility—the Geological Time Scale no longer accurately reflects Earth history.

The AWG has not gone away. It continues operations as an independent group, and has published several important papers since the ICS and IUGS rulings.27 Like Charles Darwin in another time, they are challenging a scientific establishment that is bent on protecting an unscientific worldview—a difficult but essential contribution to the advancement of science.

Eight years before the top bureaucrats in organized geology made their decision, I closed a summary of Anthropocene debates with these words:

It is still possible that the usually conservative International Commission on Stratigraphy will either reject, or decide to defer, any decision on adding the Anthropocene to the geological time scale, but as the AWG majority writes, “the Anthropocene already has a robust geological basis, is in widespread use, and indeed is becoming a central, integrating concept in the consideration of global change.…”

In other words, failure to win a formal vote will not make the Anthropocene go away.28

Since I wrote that, the volume and persuasiveness of the evidence has only grown. The highest temperatures in human history, species extinctions on an unprecedented scale, a global glut of plastics and synthetic chemicals that nature cannot absorb, multiple pandemics of previously unknown diseases, and many more crises confirm that massive disruption of Earth’s life support systems is underway, in a new and deadlier stage of planetary history.

The Anthropocene may not be official, but it is real.

Notes

1.  Stephen Barker et al., “Distinct Roles for Precession, Obliquity, and Eccentricity in Pleistocene 100-kyr Glacial Cycles,” Science 387, no. 6737 (February 28, 2025).
2.  Thomas Slater et al., “Review Article: Earth’s Ice Imbalance,” Cryosophere 15 (January 25, 2021): 233–46.
3.  C. P. Summerhayes et al., “The Future Extent of the Anthropocene Epoch: A Synthesis,” Global and Planetary Change 242 (November 2024): 104568.
4.  Will Steffen, Paul J. Crutzen, and John R. McNeill, “The Anthropocene: Are Humans Now Overwhelming the Great Forces of Nature?,” Ambio 36, no. 8 (December 2007): 614.
5.  Barbara Ward and Rene Dubos, Only One Earth: The Care and Maintenance of a Small Planet (New York: W. W. Norton, 1972), 12.
6.  For a detailed scientific evaluation, see Toby Tyrrell, On Gaia: A Critical Investigation of the Relationship Between Life and Earth (Princeton: Princeton University Press, 2013).
7.  National Research Council, Earth System Science—Overview: A Program for Global Change (Washington, DC: National Academies Press, 1986), 4.
8.  National Research Council, Global Environmental Change: Research Pathways for the Next Decade (Washington, DC: National Academies Press, 1999), 3.
9.  Juan G. Roederer, "ICSU da luz verde a IGBP", Eos 67, no. 41 (14 de octubre de 1986): 777–81.
10.  Programa Internacional de Geosfera y Biosfera, IGBP Cambio Global: Los Proyectos Básicos Iniciales, Informe no. 12 (Estocolmo: Consejo Internacional de Uniones Científicas, 1990), 1–3.
11.  He descrito este proceso con más detalle en el primer capítulo de Frente al Antropoceno (Nueva York: Monthly Review Press, 2016).
12.  Will Steffen et al., "El surgimiento y la evolución de la ciencia del sistema terrestre", Nature Reviews Earth & Environment 1 (enero de 2020): 59.
13.  Martin Head et al., "La gran aceleración es real y proporciona una base cuantitativa para la serie/época del Antropoceno propuesta", Episodes Journal of International Geoscience 45, no. 4 (diciembre de 2022): 359–76.
14.  Will Steffen et al., El cambio global y el sistema terrestre: un planeta bajo presión (Nueva York: Springer, 2004), 93.
15.  Steffen, Crutzen y McNeill, "El Antropoceno: ¿Están los humanos ahora abrumando a las grandes fuerzas de la naturaleza?", 617.
16.  Andrey Ganopolski y Stefan Rahmstorf, "Cambios rápidos del clima glacial simulados en un modelo climático acoplado", Nature 409 (11 de enero de 2001): 153–58.
17.  William J. Burroughs, Cambio climático en la prehistoria: el fin del reinado del caos (Cambridge: Cambridge University Press, 2005), 13, 102.
18.  J. R. Petit et al., "Historia climática y atmosférica de los últimos 420.000 años del núcleo de hielo de Vostok, Antártida", Nature 399 (3 de junio de 1999): 429–36.
19.  “Declaración final de la Conferencia Planet Under Pressure, Londres, 2012", EarthSky, 29 de marzo de 2012, earthsky.org.
20.  Colin N. Waters et al., "El Antropoceno es funcional y estratigráficamente distinto del Holoceno", Science 351, no. 6269 (2016).
21.  Matthew Edgeworth et al., "El Antropoceno es más que un intervalo de tiempo", Earth's Future 12, 18 de julio de 2024.
22.  Jan Zalasiewicz et al., "Respuesta a Edgeworth et al. 2024: El Antropoceno es un intervalo de tiempo, y más además", ESS Open Archive, 23 de diciembre de 2024.
23.  Jan Zalasiewicz et al., "Argumentando a favor de una época formal del Antropoceno: un análisis de las críticas en curso", Newsletters on Stratigraphy 50, no. 2 (abril de 2017): 205–26.
24.  Jan Zalasiewicz, prólogo a Martin Bohle, Boris Holzer, Leslie Sklair y Fabienne Will, El Grupo de Trabajo del Antropoceno y el debate global en torno a una nueva época geológica (Nueva York: Springer, 2025), ix, xii, xiv.
25.  Todd J. Braje y Jon M. Erlandson, "Mirando hacia adelante, mirando hacia atrás: humanos, cambio antropogénico y el Antropoceno", Antropoceno 4 (diciembre de 2013): 116–21.
26.  Stanley C. Finney y Lucy E. Edwards, "La época del 'Antropoceno': ¿Decisión científica o declaración política?", GSA Today 26, no. 3 (marzo de 2016): 4–10.
27.  Entre otros: Summerhayes et al., "La extensión futura de la época del Antropoceno"; Francine McCarthy, Martin J. Head, Colin N. Waters y Jan Zalasiewicz, "¿Importaría agregar el Antropoceno a la escala de tiempo geológico?" AGU Advances 6, no. 2 (febrero de 2025); Mark Williams et al., "Las firmas paleontológicas del Antropoceno son distintas de las de épocas anteriores", Earth-Science Reviews 225 (agosto de 2024): 104844.
28.  Angus Frente al Antropoceno, 58.