Back to the future: climate change lessons from the Pliocene era

Of the many clichés passed from generation to generation, “You must understand your past in order to understand your future” is both the most intuitively correct and consistently ignored.

Too often the historian’s excavation of the past is considered to be of merely academic interest rather than a stark warning about the social, political and economic conditions that can re-enable historic calamities.

Dr Chris Brierly (UCL Geography), who delivered the Lunch Hour Lecture on 13 February, is pursuing historical research to help us comprehend our past and possibly safeguard our future from devastation.

Instead of looking back 100 years at Franz Ferdinand’s assassination, Brierly looks back 5 million years, when the world was curiously similar yet significantly different to the one we inhabit today.

Brierly explained how his research concentrates on mapping the tropical climate of the Pliocene epoch, which began around 5 million years ago and ended 2.6 million years ago.

Just like the present, the Pliocene world was both warm and cool: grassland expanded and ice-caps accumulated. It did, however, have a structurally different tropical sea climate.

This discrepancy shows how Brierly’s research has implications for our immediate future.  The fact that in spring last year carbon dioxide concentrations in our atmosphere passed “400 parts per million” – a level not seen since the Pliocene era – only highlights this.

If current carbon-emitting current trends continue, Brierly argues we could be looking at a similar tropical oceanography to that of the Pliocene, one defined by vast pools of warm water stretching across the Pacific and Indian Ocean.

This shift towards large areas of warm ocean water, as opposed to the sporadic, localised warm water typical today, could lead to significant rainfall and atmospheric changes, endangering human societies.

Fascinatingly, the lecture explained how climate scientists illuminate the past. Whereas a historian may fight for access to guarded archives, climate scientists drill long cylinders of mud from the ocean floor and analyse the chemical content to discern a passage of time.

Brierly also detailed a method for mapping past carbon dioxide levels by examining the size of stomata, the pores that regulate gas exchange, in fossilised leaves. These innovative attempts at time-travelling are a testament to the creativity of the best scientists.

Brierly’s strongest rhetorical device was his modesty: far from prioritising his thesis above others, he was faithful to the tenets of the scientific method. It was great to hear him emphasise the possible epistemic and methodological uncertainties of his own analysis.

He said that it’s possible the computer mapping software he uses, essential in projecting climactic outcomes, could be flawed or that their collected data is incorrect. He rightly pointed out that the former would be quite worrying as the software he uses at UCL is the same one used by the UN’s International Panel on Climate Change.

The closing words of Brierly’s talk were designed to shake his audience out of an academic slumber: he said, “I don’t want to live in a Pliocene climate”. If we want to reduce the possibility of an unstable future climate, “we need to act now, not in thirty years”.

As flooding in Britain evolves from the peculiar to the perennial, climate change has once again gripped our ever-shortening attention spans. Perhaps the one beneficial outcome of the floods will be its reiteration of the interdependence between suburban and agricultural development and climate. Hopefully, forever discrediting the scepticism about the link between human activity and weather, which permeates our  daily subconscious.

But what happens when the floods subside? The implication of Brierly’s conclusion depended on his audience’s capacity to fuse short-term and long-term logic: to act now for tomorrow.

This crucial question occupied me for a full five minutes after the lecture, until I went to Sainsbury’s to get a meal deal and discovered there were no more Hoisin duck wraps. And the queue for the self-service checkout was massive.

Wait, what were we talking about again?

Homepage image: An ideal landscape of the Pliocene period (Riou) Source: Wellcome Library, London