Scientists say 'new era' of humanity's adverse impact on Earth began in 1950s

Scientists have designated a small body of water near Toronto, Canada as ground-zero for the 'Anthropocene era' – the proposed geological epoch defined by humanity's massive and destabilising impact on the planet – which they say began at the beginning of the 'atomic age' in the 1950s. 

Humans' impact on the earth began a new epoch in the 1950s – called the Anthropocene – when massive nuclear testing was carried out in the Marshall Islands in the South Pacific. © Atomic Heritage Foundation

From climate change to species loss and pollution, humans have etched their impact on the Earth with such strength and permanence since the middle of the 20th century that a special team of scientists says a new geologic epoch began then.

Called the Anthropocene – derived from the Greek terms for “human” and “new” –scientist believe this epoch started sometime between 1950 and 1954.

While there is evidence worldwide that captures the impact of burning fossil fuels, detonating nuclear weapons and dumping fertilizers and plastics on land and in waterways, the scientists have proposed a small but deep lake outside of Toronto, Canada – Crawford Lake – to place a historic marker.

Layered sediment at the bottom of Crawford Lake – laced with microplastics, fly-ash spread by burning oil and coal, and the detritus of nuclear bomb explosions – is the single best repository of evidence that a new, and challenging, chapter in Earth's history has begun, members of the Anthropocene Working Group concluded on Tuesday. 

Scientists advance their case for defining a new chapter in Earth's history: #Anthropocene https://t.co/El6exn7od2 via @axios

— The Anthropocene Project (@anthropocene) July 11, 2023

According to Andy Cundy, a professor at the University of Southampton and member of the working group, "The data shows a clear shift from the mid-20th century, taking Earth's system beyond the normal bounds of the Holocene" – the epoch that began 11,700 years ago as the last ice age ended.

After years of deliberation, the Canadian lake was selected from among 12 candidate sites around the world – including another lake, coral reefs, ice cores and an ocean bay in Japan – as the Anthropocene's so-called "golden spike". 

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The chairman of the Anthropocene Working Group, UCL professor Simon Turner, said "The sediment found at the bottom of the Crawford Lake provides an exquisite record of recent environmental change over the last millennia.

"It is this ability to precisely record and store this information as a geological archive that can be matched to historical global environmental changes."

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And those changes are currently on dramatic display: last week was the hottest globally on record.

Out-of-control forest fires have been ravaging Canada for months, while the US and China are coping with unprecedented heat, flooding and drought at the same time.   

Humanity has burned so much fossil fuel that concentrations of planet-warming CO², meanwhile, have increased by half. 

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Sea surface temperatures have hit new highs in recent weeks, and last month recorded that Antarctic sea ice was 17 percent below the previous record low for June.

In June, scientists reported that so much water has been pumped from underground reservoirs that Earth's geographic North Pole has shifted by nearly five centimetres per year. 

Has Earth entered the age of humans? The Anthropocene Era © Gal ROMA / AFP

'Great Acceleration'

According to the rules of the International Commission on Stratigraphy, which in 2009 mandated a team of geologists to assess evidence for the Anthropocene, there must be a synchronous "primary marker" for a proposed boundary that is detectable in the geological record almost anywhere on the planet.

For the Anthropocene, plutonium cast off by hydrogen bomb tests provides that "global fingerprint," Cundy explained.

"The clearest marker for a single year – which gives an abrupt and effectively instantaneous snapshot – is plutonium, because there's so little of it naturally present."

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That means 1952 – when the United States first detonated a huge hydrogen bomb in the Marshall Islands as a test – could become the Anthropocene's boundary year.

Smaller atomic explosions before that left mostly regional imprints.

A sharp, almost 90° increase across a dozen markers of humanity's growing impact – including population, water use, greenhouse gas emissions, and forest loss – that converged around the middle of the 20th century add up to what scientists call the "Great Acceleration." 

Breaking!

Anthropocene Golden Spike:
> Anthropocene Epoch begins in 1950
> Marked by Plutonium isotope.
> Site = Crawford Lake, Canada

Proposed by Anthropocene Working Group of @ICS2022 today.https://t.co/kejYeIX9Ky pic.twitter.com/wFT7NfXgFW

— Erle Ellis (艾尔青) (@erleellis) July 11, 2023

The "epoch of humans" first proposed in 2002 by chemistry Nobel Paul Crutzen is widely accepted within science as a reality, but faces daunting hurdles for formal validation by the gatekeepers of Earth's official geological timeline of eons, eras, periods and epochs, such as the Jurassic and the Cretaceous.

The recommendations must be approved by super-majority vote of two separate committees before final validation by the International Union of Geological Sciences.

The heads of those bodies have thus far expressed sharp scepticism towards the Anthropocene, mostly on technical grounds.

However, scientists who announced Crawford Lake as a benchmark said they hoped Tuesday's decision would encourage people to think more deeply about their responsibility to the planet.