Have humans triggered a new geologic era? Geologists disagree if the Anthropocene exists or not

Earth's 4.5 billion year geological history is full of death and rebirth, mass extinctions and explosions of biodiversity, with different periods often marked by cataclysmic changes that radically reshaped environments and climates. Whether it was major ice ages or meteor impacts, these changes encompass everything from the shape of our continents to the composition of our oceans.

One of the biggest ongoing debates in science is whether or not human activity, such as burning fossil fuels and triggering climate change, has had enough of an impact to create what can be considered a new geologic era. After all, scientists repeatedly remind us that our rapidly-heating planet is sending us into "uncharted territory" as we regularly break heat records and seem to be triggering a mass extinction some have called a "biological holocaust."

The scientific consensus is that people have lived in the Holocene epoch for roughly 11,700 years, but some scientists argue human activity like mass extinctions, climate change, plastic pollution and nuclear fallout have fundamentally altered the planet, creating a new geological epoch in the process. Will our devastation ripple through the future for millions or even billions of years? Some argue yes, and this new era has been dubbed the "Anthropocene." But other experts have pushed back against this label, suggesting it's too soon to say whether or not our carbon footprints will be washed away in the waves of time.

In March 2024, the International Union of Geological Sciences (IUGS) aroused controversy when they voted down a proposal to officially call our evolving geological epoch the Anthropocene. The IUGS decision provoked heated debate within the scientific community about its accuracy.

While an overwhelming majority of experts agree that climate change is anthropogenic — that is, human-caused — not everyone is so certain our influence is as dramatic or influential as some make it out to be, at least on geological timescales.

In 2001, atmospheric chemist Paul Crutzen was first to dub this alleged new epoch the Anthropocene, and by 2009 a multidisciplinary team of scientists known as the Anthropocene Working Group (AWG) was formed to determine whether Crutzen's theory is correct. After 14 years of research, the AWG decided that humanity began living in the Anthropocene starting in 1952, a year they chose because a stratotype section at Crawford Lake, Canada revealed a sharp upturn in sedimental plutonium concentrations from thermonuclear bomb testing occurring all over the world at that time.

But the IUGS disagrees this constitutes enough global impact to be a formal unit of the Geologic Time Scale.

"It is extremely disappointing that 14 years of research and the data compiled by the AWG and included in our submission were overlooked by many of the voting members of SQS [the Subcommission on Quaternary Stratigraphy]," Dr. Colin Waters, who chaired the AWG and is an honorary geography and geology professor at the University of Leicester, told Salon. He alleged that the voting process was so flawed as to be "illegitimate," arguing it should have been suspended until suitable reforms were implemented. Indeed, Waters argues that seemingly unprofessional behavior continues to this day.

"We believe that our official Anthropocene Working Group has been disbanded by ICS [the International Commission on Stratigraphy], though again they have not felt it of importance to notify us of this," Waters said. "A proposal can be submitted at a future date only if a new working group is established by the governing bodies. There is no time limit on when this can be done, but it does require those bodies to be sympathetic to the idea of investigating this further in the future." Waters expressed hope that, when the current executives of the IUGS' various bodies leave their offices, their replacements will be more sympathetic.

"Irrespective of the vote, the AWG stands fully behind its proposal," Waters said. The AWG demonstrated "beyond a reasonable doubt" that the "relatively stable interglacial conditions" that existed since the start of the Holocene Epoch 11,700 years ago no longer exist because of human activity; that the changes are irreversible; that geological strata associated with these changed conditions are "distinct from Holocene strata"; and that the plutonium concentrations from the stratotype section at Crawford Lake, Canada have been confirmed by precisely similar results in strata around the world.

"All these lines of evidence indicate that the Anthropocene, though currently brief, is – we emphasize – of sufficient scale and importance to be represented on the Geological Time Scale and terminating the Holocene," Waters said.

Dr. Martin Head, a professor of Earth sciences at Brock University, said that the IUGS decision is "very strange," characterizing it as occurring through a seemingly "illegitimate process" that he "must accept but cannot approve." Head said he was puzzled by the objections to formalizing the term "Anthropocene."

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"The main objection seems to be that the Anthropocene as a new epoch is too short (at around 72 years) and that the future is not geological time (which starts with the present and extends backwards)," Head said. "These are both true of course. But the future will surely become geological time and we have firm evidence from Earth System science that conditions outside of Holocene norms will persist for tens of thousands of years."

Head also observed that "professional jealousy" seems to be a factor in this debate, as "the Anthropocene attracts a great deal of attention because of its links to climate change. My sense is that other stratigraphers working in deeper time feel eclipsed."

Regardless of the other stratigraphers' feelings, though, Head is convinced that the Anthropocene concept is both scientifically valid and socially useful.

"The Anthropocene as a new unit of the time scale formally acknowledges that our planet has been forced into a new functioning trajectory," Head said. "It left the old trajectory in the mid-20th century as a result of overwhelming human impacts. Without acknowledging this, humans risk not taking ownership of the problem and doing too little to ameliorate our future footprint."

Dr. John Vidale, a geophysicist at the University of Southern California, also told Salon that "an Anthropocene epoch makes good sense." Vidale said that "etching mankind’s impact on the environment with a term that would gain popularity and be backed by a scientific definition would highlight the bad (and good) changes in our planet, some of which are by choice. The existence of the Anthropocene would make it harder to deny or push under the rug."

Dr. Erle Ellis, a professor of geography and environmental systems at the University of Maryland, told Salon the Anthropocene is a "critical concept for science communication about anthropogenic global change, so it really matters how it is portrayed."

He told Salon that the people who care about the evidence already accept that humanity is changing the planet irreversibly, and an "official" label will not alter public perceptions. "In fact, the hardest thing to explain to people is why 1952 is relevant to this — or why a dozen centimeters of sediment in a lake in Canada can represent the Anthropocene better than all the other evidence," Ellis said. "In other words, in the end, this discussion about a formal epoch is a dead end. It's time to move on with the science of the Anthropocene. And most of the public never knew this discussion existed — just like most of the public don't know what epoch they officially live in (the Holocene) — because it doesn't really matter."

At the same time, even Ellis acknowledges that the concept of an Anthropocene is useful for scientists, though he argues if it should not be formalized as a geological epoch.

"It is really important right now to clarify that the Anthropocene remains an important scientific concept and that geologists accept it (as a geological event)," Ellis said. "The only thing that happened with the vote is that the 'Anthropocene epoch' was not formally defined in the Geologic Time Scale. 'The Anthropocene' remains just the same as it was before the vote."

The President of the IUGS, professor John Ludden CBE, said essentially the same thing in the statement shared with Salon about their decision.

"Despite its rejection as a formal unit of the Geologic Time Scale, Anthropocene will nevertheless continue to be used not only by Earth and environmental scientists, but also by social scientists, politicians and economists, as well as by the public at large," Ludden said. "It will remain an invaluable descriptor of human impact on the Earth system."

These reassurances seem to be cold comfort to people like Waters, who characterized attempts to play Devil's Advocate by understanding the IUGS position as efforts "to defend the indefensible."

"There are many examples of previous paradigm shifts in science, such as evolution and plate tectonics, where some geologists have proved reluctant to accept the overwhelming evidence," Waters said. "Darwin was fortunate that he did not have to get his theory approved by committee."