The Past Can’t Tell You the Future

Eemian Days

July 2023 was the hottest month since the Eemian interglacial. This period, which ended some 120,000 years ago, was about 1–2 degrees warmer than today’s pre-industrial baseline. In other words, it had an average temperature that is rapidly becoming our own.

The Eemian world was one that might have looked familiar to us. Almost all the fauna and flora that exists today was already present, and hunter-gatherer humans were widespread. But the familiarity was only at a glance. Hippos wallowed in the Thames River, Europe’s native elephants (Palaeoloxodon antiquus) roamed from Wales to Russia, and Scandinavia was an island.

With the repeat of similar temperature conditions today, many have been looking to the aforementioned Eemian to predict what our future conditions will look like. Others look further back, to the mid-Pliocene 3.3 million years ago, when temperatures were within the range we are expected to reach on current climate trajectories (2–3 °C warmer). “The answer [to the future] lies in…studying the Pliocene epoch” according to the scientist Rich Pancost. Another study considered the Pliocene a good proxy for what a ‘stabilized’ future climate future might look like, but:

“If a planetary threshold does indeed exist, the current trajectory might lead us directly towards a Hothouse Earth…This would put the Earth System in a state similar to that of the Middle Miocene (some 15–17 million years ago)”

This projection of past conditions into our future is appealing in that it (seemingly) provides answers. But this method falls apart the more closely one looks. The Eemian period had a green, verdant Sahara, whereas today only desert now stands — and expands. Northern Europe was far hotter in the Eemian, but Southern Europe was notably cooler than today. Coral reefs thrived, whereas today hotter conditions are causing mass die-offs. Despite the increased temperatures for tens of thousands of years, none of the global tipping points we are now approaching seem to have been triggered. Icecaps remained, the permafrost stayed frozen, and the Amazon rainforest did not flip to a dry savannah state.

The projection becomes even less accurate the further we look back. The Pliocene was characterized by a distinctive drying trend, whereas one of the most dangerous factors of contemporary climate change is how it is supercharging the atmosphere with moisture—leading to more severe storms and flooding. The past was its own world, and one that did not react to climatological stimuli in the same way our own times will.

Discontinuity is the Game

As tempting as it is to look for precedents to unfamiliar change, you cannot wring futurology from paleontology. The past offers important lessons, of course, but assuming a common course ignores quite how exceptional our own times are.

Whilst greenhouse gases have raised global temperatures before, they have never been emitted as rapidly as today. Not during the Eemian, not during the Eocene thermal maximum, nor even the Permian Great Dying — Earth’s worst-ever mass extinction. Likewise, the rapidity of climate change today is unprecedented. Aside from the asteroid that ended the Cretaceous period, the climate has never changed this rapidly.

New research suggests that the speed of change in a climate system has as much effect on the outcome as the overall scale of change. The faster we change, the more unfamiliar and more devastating the outcome will be. It’s like the difference between crashing your car at 50 mph, or at 100. The end result is directly related to how we get there.

Neither are we entering this era of change with the same ecological integrity as past climacterics [1]. The biospheric system is not a passive subject of the climate system, but one of its fundamental building blocks. More importantly, it is a moderating and adaptive system. It is why the Pleistocene ice ages never precipitated any major (non-anthropogenic) extinctions, because our ecological system was pliable to vast climate changes. We no longer possess this adaptive capacity, and cannot rely on our degraded environments adapting or shifting to more hospitable latitudes.

Another one of the problems with basing future scenarios on the past is that it assumes climate disruption takes us to a new baseline state — a ‘new normal’ if you will. But as the futurist Alex Steffen has said:

“The most challenging aspect of this planetary crisis is exactly [it’s] erosion of stability, of predictability, of continuity… not only of the loss of “normal,” but the unlikelihood of a “new normal” arising.”

Humans don’t live on geological timescales, neither do civilizations. Equilibrium (even relatively) is only reached on such epochal chronologies. We are not destined to experience the period ‘on the other side’ of the discontinuity, only its chaotic interregnum.

Data, not Lessons

Adaptation to the unexpected is what will define the future of our societies. The more we plan as if the past will mirror the future, the worse we will be prepared. Paleontology holds data vital to understanding climate changes, but not the answers to our current climacteric.

Of course, trying as best we can to predict potential futures is vital, lest we be caught off guard. But we cannot work off of precedent. Neither the Eemian nor Pliocene can tell us what we need to adapt to, much less give us any indications of how. Whatever climate emerges over the coming decades and centuries, it will bear little relation to our past. If we are to survive, the same must be true of us.

Notes

[1] Climacteric: A stage in the life of a system in which it is especially exposed to a profound change in health or fortune.