Citizen Writes
Research hot topics
Humanity’s energy binge has pushed back Earth’s next Ice Age
2024-11-19
By Professor Jan Zalasiewicz, Honorary Professor Colin Waters, Professor Mark Williams and Professor Jens Zinke, School of Geography, Geology and the Environment
We are not living on the same planet as our great-grandparents, as they grew up in pre-WWII times, or any of our ancestors back through recorded history. That is the message of the proposed Anthropocene epoch in which, due to human impacts that have become overwhelming since the mid-20th century, the Earth is now hotter, more biologically degraded and polluted. And so, it has become less sustainably habitable for both humans and non-humans.
But is this just a blip? – a brief planetary stumble from which the Earth will soon bounce back to resume its former condition, that of the Holocene Epoch that reigned and nurtured human civilization for more than 11 millennia after the ice caps last receded? A newly published synthesis, led by Colin Summerhayes of the Scott Polar Research Institute at the University of Cambridge, working with colleagues of the Anthropocene Working Group that includes us, shows, rather, that the course of Earth history has been fundamentally shifted, not least as regards its climate state. The Anthropocene is here to stay, over geological timescales.
Greenhouse gas emissions have soared since the mid-20th century, to our knowledge faster than at any time in Earth history. Carbon dioxide levels are now higher than at any time in the last three million years, and if one factors in the effect of methane, also now sky-rocketing. The nearest comparison may be 15 million years ago in the warm Miocene Epoch, when much of the Antarctic ice sheet melted. The Earth’s resulting energy imbalance (where more heat is gained than lost by the planet) is now more than a watt each square metre. It has led to the Earth now being about 1.5° Celsius warmer than in pre-industrial times, fuelling extreme weather that now continually hits the headlines. Polar ice is melting, sea levels are rising, and ecosystems worldwide are being devastated – and the energy imbalance means that more heat is in the pipeline.
Modelling the Earth’s perturbed climate into the far future means that humanity’s energy binge has pushed Earth’s next Ice Age to at least 50,000 years in the future – and with more greenhouse gas emissions that figure increases to half a million years. These are truly (at least) epoch-scale changes, and emphasize the reality of the Anthropocene as a new force in planetary time.
It’s not just a delay of the next Ice Age that is at stake here: if it was just a case of prolonging the kind of conditions that characterized the last 11,700 years, that typified the warmth and stability of the post-glacial Holocene Epoch in which human civilization developed, we would all be cheering. But this sudden influx of greenhouse gases has already made this a hotter world than at any time in the Holocene, and this threatens to intensify, to take us back into the kind of hothouse world in which the dinosaurs lived: a very different and more hostile kind of planet. And, we must recall that this sudden, drastic ratcheting up of the greenhouse effect is coming on top of, and adding to, other recent forms of human-induced global biological mayhem, such as through widespread habitat loss and myriad species invasions, as described in another recent major paper on the Anthropocene led by one of us (Mark Williams). Global warming is even now taking millions of species out of their comfort zones, and many are already perishing from its effects: either literally being unable to take the heat; by being starved out of existence as food chains are dislocated; or, succumbing to the myriad pollutants that we have released into the environment.
It is becoming increasingly clear that the climate crisis and the global biodiversity crisis are two sides of the same coin: of a brutal shift in planetary conditions, reducing the Earth’s habitability. Their close relation is already the focus in commentary on the recent COP16 summit on biodiversity in Colombia and the COP29 climate summit in Azerbaijan. One cannot address one problem without working on the other. And to address them properly, we need to comprehend the nature of the Anthropocene as a truly new (even if still informal) planetary epoch, one that that we are researching as part of an international effort involving many scholars, across a wide range of disciplines.
What to do? Clearly, human societies must adapt to the new conditions, and prepare for the long haul. It would be prudent, too, to quickly and severely restrict further greenhouse gas emissions, so the Earth does not become the kind of extreme hothouse which triggered mass extinctions in the geological past. Human civilization really is at stake, and every tenth of a degree, and every local ecosystem protected, really do count.