By Dr Catriona Nguyen-Robertson MRSV
Senior Editor, Science Victoria
with Mike Flattley
CEO, The Royal Society of Victoria

There is an argument made by planetary scientists that we are living in a new epoch of geological time, one of our own making. The term ‘Anthropocene’ (anthropo meaning ‘human’) has been proposed as a new geological epoch that describes this recent period of Earth’s history, in which humans have significantly impacted the planet’s climate and ecosystems.

The term was formally coined in 2000 by biologist Dr Eugene Stoermer and atmospheric chemist and Nobel Laureate Dr Paul Crutzen. They proposed that we began moving away from the Holocene, the current epoch of a stable, accommodating climate that has lasted for 11,700 years since the end of the last major ice age, with the commencement of the industrial revolution in 1750. This view correlates with the buildup of greenhouse gases observed in ice core samples representing the period.

There has been sustained and intense debate among the scientific community as to whether the industrial era, or even the post-WWII years of the 20th century, should be officially designated as the beginning of a new geological epoch. To be classified as such, it must be demonstrated that human activities have impacted the planet to the extent that changes are reflected in the rock strata.

In 2009, an interdisciplinary Anthropocene Working Group of researchers was established within the International Commission on Stratigraphy, which oversees the official geologic time chart. The Working Group voted to accept the idea in 2019, and work to provide scientific evidence robust enough for the Anthropocene to be formally ratified by the Commission’s parent body, the International Union of Geological Sciences (IUGS), as an Epoch within the Geologic time scale.¹

In late 2023, referencing the geochemical changes to sediments at the bottom of Crawford Lake in Ontario, Canada, the Working Group submitted its proposal to a governing committee of the IUGS, who voted not to support the definitions presented by the Working Group as a fitting signpost of when, and how, a proposed new epoch began.

According to the New York Times, IUGS committee member and Earth scientist Professor Mike Waller argued that “human impact goes much deeper into geological time. If we ignore that, we are ignoring the true impact, the real impact, that humans have on our planet.”²

The Working Group did indeed take a holistic look at human impacts. Modern human activity skews the chemistry of the Earth’s atmosphere, oceans, and environment – rapidly and drastically. They examined socio-economic and Earth System trends (e.g. greenhouse gas emissions, climate, coastal zones, and biosphere integrity), all of which demonstrate a ‘Great Acceleration’ towards a hotter climate system and a degraded, ill-functioning biosphere.³

In 2021, the late Professor Will Steffen presented his climate science work to the Royal Society of Victoria, demonstrating that ‘the Anthropocene is not stable. It is trajecting away from the Holocene.’ The current rate of temperature and atmospheric carbon dioxide increase is almost unprecedented in Earth’s entire 4.5-billion-year geological history. The only other time global temperatures and conditions changed this dramatically was when an asteroid hit the area now known as the Yucatan peninsula in the Gulf of Mexico, 66 million years ago, famously triggering an age of mass extinction and a rapid increase of 5 °C in global temperatures that lasted for roughly 100,000 years.⁴

This asteroid impact is neither characterised as an epoch nor as an era in geological time. It was an event that catalysed a very dramatic global change, which is the point many scientists are now making: our planet is currently in a fast transition to a new state. It is an event that is yet to settle into new, long-term patterns that will define the ‘new normal’ for planetary systems, either as an epoch or as a far more dramatic change in state that establishes entirely new cycles and interactions between the Earth’s systems.

This is a slow process for us to observe on the scale of human lifetimes, but it happens in the blink of an eye from the perspective of planetary history. While we can continue to informally refer to the event we’re all living through as ‘the Anthropocene,’ for now the formal geological epoch remains ‘the Holocene.’

Reaching a tipping point 

The Paris Agreement of 2015 is an international treaty with the aim of limiting global warming to 1.5 °C above pre-industrial levels. Many climate prediction models suggest that we will reach a warming of 3 °C – or, at worst, 4.5 °C – on our current trajectory towards the end of the 21st century. While climate change has been a feature of our planet since it established oceans and an atmosphere, most life on Earth has not evolved to adapt to such rapid changes in conditions. Crucially, once a certain point is reached, Earth’s systems will have been set in motion to all reach a cascading “tipping point” – and there will be no going back.

All of Earth’s systems are connected. The cascade is likened to a line of dominos falling down if only one is knocked over. If the northern ice sheets melt, the influx of fresh water will destabilise the North Atlantic jet streams, a key part of global heat and salt transport by the ocean. This will in turn destabilise the West African monsoon, triggering drought, and reduce rainfall over the Amazon. It could also disrupt the East Asian monsoon and cause heat to build up in the Southern Ocean, which could accelerate Antarctic ice loss. Alarmingly, this is already happening.⁵

Prof Steffen was a part of a team of 29 internationally renowned scientists who first proposed the nine planetary boundaries for processes that regulate the stability and resilience of the Earth system. Crossing these boundaries increases the risk of generating large-scale, abrupt, or irreversible environmental changes that will most likely contribute, in turn, to the decline or collapse of civilisation.⁶

He warned us that we are approaching a fork in the road, where our emissions and actions will determine Earth’s future. Whether our descendants inherit a stabilised Earth with a moderate climate or a more hostile “hothouse” Earth is now up to our generation. We must avoid pushing the planet beyond a tipping point from which there is no return.⁷

Avoiding this tipping cascade requires fundamental changes to society. Equity problems between nations need to be taken into consideration rather than swept under the carpet, given that there is a correlation between a country’s relative wealth and its contribution to pollution and carbon emissions.⁸

Working towards a more sustainable future requires not only advances in science and technology, but also more fundamental changes in societal structures and core values. Prof Steffen urged a move towards the ‘Doughnut framework’ developed by economist Kate Raworth, which proposes an economy that supports the needs of people without overshooting the Earth’s ecological boundaries.⁵ Ultimately, we should shift from a human-centric focus to a life-centric focus.¹⁰

Prof Steffen reminded us that Aboriginal and Torres Strait Islander people have already been doing this in Australia for over 65,000 years. They represent the only human cultures to maintain ancestral traditions through an ice age and into the interglacial period of the Holocene. They have developed methods for low-impact adaptation and ways of nurturing the land over millennia. Listening to and learning from the persistence approach of Indigenous Australians might illustrate the way forward towards a more life-centric society.

Evidence gathered by Professor Will Steffen and many other accomplished scientists reveals that we are already in a state of planetary emergency. We have to act now to avoid pushing Earth’s systems to their limit, or else ‘we might tip the whole planet’.

This updated article follows a presentation to the Royal Society of Victoria on 8 April 2021 titled “The Anthropocene: Where on Earth are we going?” delivered by Professor Will Steffen (Australian National University). You can view Will’s presentation online at youtube.com/watch?v=HvD0TgE34HA

References:

1. Macmillan. (2019, May 21). Anthropocene now: influential panel votes to recognize Earth’s new epoch. Nature News. nature.com/articles/d41586-019-01641-5
2. Clem, K., Massom, R., Stammerjohn, S., & Reid, P. (2022, Aug 2). Antarctic Sea Ice #1: Physical Role and Function. (N. Gilbert, Ed.) Cryosphere. doi.org/10.48361/tqhw-c793
3. Lenton, T., Rockström, J., Gaffney, O., Rahmstorf, S., Richardson, K., Steffen, W., & Schellnhuber, H. (2019, Nov 27). Climate tipping points — too risky to bet against. Nature, 575, pp. 592-595. doi.org/10.1038/d41586-019-03595-0
4. MacLeod, K. G., Quinton, P. C., Sepúlveda, J., & Negra, M. H. (2018, May 24). Postimpact earliest Paleogene warming shown by fish debris oxygen isotopes (El Kef, Tunisia). Science, 360, pp. 1467-1469. doi.org/10.1126/science.aap8525
5. Raworth, K. (2012). A Safe and Just Space for Humanity: Can we live within the doughnut? London: Oxfam. Retrieved Mar 20, 2024, from www-cdn.oxfam.org/s3fs-public/file_attachments/dp-a-safe-and-just-space-for-humanity-130212-en_5.pdf
6. Richardson, K., Steffen, W., Lucht, W., Bendtsen, J., Cornell, S. E., Donges, J. F., . . . Rockström, J. (2023, Sep 13). Earth beyond six of nine planetary boundaries. Science Advances, 9(37). doi.org/10.1126/sciadv.adh2458
7. Steffen, W., Broadgate, W., Deutsch, L., Gaffney, O., & Ludwig, C. (2015, Jan 16). The trajectory of the Anthropocene: The Great Acceleration. The Anthropocene Review, 2, pp. 81-98. doi.org/10.1177/2053019614564785
8. Taconet, N., Méjean, A., & Guivarch , C. (2020, Feb 26). Influence of climate change impacts and mitigation costs on inequality between countries. Climatic Change, 160, pp. 15-34. doi:doi.org/10.1007/s10584-019-02637-w
9. Zhong, R. (2024, March 05). Are We in the ‘Anthropocene,’ the Human Age? Nope, Scientists Say. Retrieved March 20, 2024, from The New York Times: nytimes.com/2024/03/05/climate/anthropocene-epoch-vote-rejected.htm

This article was prepared by Catriona Nguyen-Robertson, and follows a presentation to the Royal Society of Victoria on 8 April 2021 titled “The Anthropocene: Where on Earth are we going?” delivered by Professor Will Steffen (Australian National University). First published 4 May, 2021, revised and republished on 2 April, 2024.