Extract from ABC News
The Ivy Mike test, where the first hydrogen thermonuclear device detonated, is argued by some geoscientists to be the start of a new geological epoch. (Supplied: US National Nuclear Security Administration)
In short:
Anthropocene is a popular term for the current time in history but is not an official geological age.
A proposal put forward by a group of scientists in 2024 to declare when the epoch started was rejected.
What's next:
The scientists said the decision was flawed and voting should be opened up more widely.
In 1952 the first full-yield test of a hydrogen bomb erupted not far from Naoero, mushroom cloud billowing above the Pacific Ocean.
That first test, and many more, spread plutonium-239 and -240 around the world marking the moment Earth entered a new era of humanity known as the Anthropocene.
At least that's according to a group of scientists who have spent years trying to pin down a date.
Georg Schäfer, a geoanthropologist, from the Max Planck Institute said that the Anthropocene moves from the period when "agriculture, cities, and human culture developed" into an era of "industrialised humanity".
"The particular strength of the Anthropocene is that it brings the many crises of the present into a single analytical frame," Dr Schäfer said.
"From coral reefs dying to microplastic pollution, climate change and forever chemicals."
But while the term has been used in popular culture for more than two decades, the Anthropocene is not an official geological epoch.
Crawford Lake in Canada was rejected as the "global boundary stratotype section and point" of the Anthropocene in 2024. (Flickr: Sean Marshall, CC BY-NC 2.0)
In 2024, a team of international scientists — the Anthropocene Working Group (AWG) — put forward evidence that the transition to a new epoch lay under the sludge at the bottom of a Canadian lake.
But the proposal was rejected by the International Union of Geological Sciences (IUGS), the peak global geosciences body, which decides what is an epoch and what is not.
"Whether it meets the criteria is not for us to judge," Dr Schäfer, an AWG member said.
"But … the evaluation by the geological institutions left too many questions open about serious procedural flaws.
"The 2024 vote was supposed to settle the scientific status of the Anthropocene. Instead, the opaque process created confusion."
The researchers have just released a new commentary, published today in the journal Earth's Future, calling for an independent review of the IUGS's process, and for the release of more records.
"It is perfectly possible that the full record would show the process was sounder than it looks from the outside, that’s a perfectly fine outcome," Dr Schäfer said.
"This closed-door approach undermines the IUGS's own authority at a moment when society depends on sound environmental science more than ever."
Why do epochs matter?
Scott Mooney, a geographer at the University of New South Wales who was not involved in the working group, said understanding when humanity's fingerprint on Earth started was a "really big question".
Currently, according to the IUGS, we are in the Holocene epoch, which started 11,700 years ago at the end of the last glacial maximum.
This period is characterised by warmer temperatures, megafauna going extinct, and humans moving from hunter-gatherer societies to farming.
This boundary between the current Holocene and the previous epoch, the Pleistocene can be seen in an ice core from the Greenland ice sheet.
Ice cores have been used as golden spikes for certain epochs. (Supplied: NASA Goddard Space Flight Center/Ludovic Brucker)
There are dozens of these boundary markers, known as global boundary stratotype section and point or "golden spikes", around the world.
The AWG selected Crawford Lake in Canada as the "golden spike" for the start of the Anthropocene, highlighting the plutonium from nuclear testing as part of a sediment core at the location.
There was supporting evidence from 11 other sites worldwide, including Flinders Reef in Queensland.
But the IUGS resoundingly rejected the proposal.
"The outcome was a decisive rejection of the Anthropocene proposal: four votes in favour; 12 votes against; and three abstentions," they wrote in a statement at the time.
"It is clear from the comments that were made during the course of the discussion period, that many were unconvinced by the arguments in the AWG proposal, and their misgivings are clearly reflected in the decisive nature of the voting outcome."
Vote exposes rift between scientists
According to Helen Bostock, an oceanographer at the University of Queensland, the voting process felt "incredibly rushed".
Professor Bostock is a member of an IUGS subcommittee and voted on the proposal.
She was one of the four people who voted in the Anthropocene's favour, but says she felt they were "kept out of the loop" for the process.
"It was like, here's the information, you must vote by next week," she said.
She said there was a "rift" between different fields of geology — those who worked in hard rocks, and those who worked in softer rocks, and this likely was spilling over to issues such as the Anthropocene proposal.
"There's some of these old-school geologists who still think that it's too soon, [that it] needs to be a decent length of time before you can actually say something changed in the past,"Professor Bostock said.
"Some of us are working on the sediments that show these human activities are having an impact on our environment. There's really no denying it when you can actually measure it and see it in your samples."
The golden spike at Enorama Creek in South Australia's Flinders Ranges which marks the boundary of the Ediacaran Period — from 635 million years ago to 542 million years ago. (Flickr: James St. John, CC BY 2.0)
Professor Bostock said that if the Anthropocene proposal was to be resubmitted, a fairer way to adjudicate would be a "broad vote" from the larger discipline rather than a small group.
"I think that would give us a much better representative, instead of a committee that might be biased in one way or another, depending on who's sitting on that committee."
Dr Mooney broadly agreed with the working group's argument about why Anthropocene should be formalised as an epoch.
"It really does highlight the impact that humanity is having on Earth," he said.
"The really good point [the group] makes is that the Anthropocene is out there — it's not just geoscientists that use [the term] — it's everyone."
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