As temperatures warmed during the PETM, plants disappeared in huge numbers from the areas that became inhospitable, appearing in wetter and cooler environments more conducive to life. In the Bighorn Basin, Scott Wing saw a shift in the thousands of plant fossils he and his team uncovered. As temperatures rose, local plants vanished from the region only to be replaced by those normally found in hotter areas, like the Gulf Coast, close to 3,000 kilometres southeast.
As in the past, global migrations are now happening due to warmer climates: pine beetles shifting north and decimating boreal forests; ticks mov- ing poleward and spreading Lyme disease. In research from Science and Nature covering four thousand species of both plants and animals globally, roughly half were escaping hotter climates and sliding poleward to colder areas. Terrestrial creatures crept north about 16 kilometres a decade, and marine species moved four times faster. The impacts of contemporary warming on agriculture could be especially transformative. “The wheat belt is going to be in Canada,” Wing says, “and not in the U.S.” He added that in some arid environments, the heat could “make the Dust Bowl era look like child’s play.”
Estimates put the number of extinctions that occurred during the PETM at around 10 per cent of all species. That might sound low to some, considering the drastic changes the planetary system went through. Wing cautions me from drawing a lesson from this. In many ways, we are still in the relatively early days of PETM research, he says, with most studies limited to specific geographic areas like the Bighorn Basin. The field is still wide open for further research, literally and figuratively.
But Wing’s words of caution go beyond this, too. Other changes during the PETM have not yet manifested today — but Wing and other experts believe they could, and they would, be significant threats to our planet. Whether they happen or not largely depends on timing.
Geologist Neil Carleton marvels at the fossils underfoot by Ottawa’s Champlain Bridge. (Photo: Javier Frutos/Can Geo)
It took anywhere from around 5,000 to 10,000 years for temperatures to rise during the PETM, all the resulting effects. Geologically speaking, that’s barely the blink of an eye. Even then, many species still had time to adapt to the higher temperatures: to shrink in size, to migrate. Despite the relative speed of warming, the adaptation process continued.
But what occurred during the PETM in thousands of years is happening now in hundreds. We are warming our planet 10 times faster than during the PETM, and so any solace we take in the relatively low PETM extinction rates should break on the shoals of our more rapidly heating reality. Two degrees over several hundred years could cause much more damage than warming over several thousand. “I can’t emphasize how important that is,” Wing says.
Zeebe, too, seems equally troubled by the current rate of warming. “How the system will react is not exactly clear,” he says.
This uncertainty extends to another issue related to timing: if, how and when the dominoes fall. While underwater volcanic eruptions and the burning of organic matter sparked the PETM, many experts are split on whether this then triggered other phenomena — such as the release of methane pockets trapped below the ocean floor or of large amounts of carbon stored in peat deposits. Wing gravitates towards this second camp, where the volcanic activity during the PETM set off chain reactions in other greenhouse gas-emitting events, further accelerating the gush of CO2 and rapid heating. “My guess is that it was, in fact, triggering something else,” he says.
I once looked at these types of scenarios — like thawing permafrost releasing stores of pent-up methane — as doomsday outliers: scary as hell but unlikely to happen. But the science on these triggers, or tipping points, is now stronger. Like a teetering Jenga tower, climate change could spark the crash of other systems. For example, the West Antarctic Ice Sheet, which contains about six per cent of the world’s fresh water, is especially vulnerable to global warming-induced collapse, which could raise global sea levels by 3.3 metres. If that happens, it could displace more than 100 million people. Scientists believe the triggering temperature for the ice sheet collapse is between 1.5 and 2 C above pre-industrial levels — and we are already at 1.2 degrees of warming. What’s more, as one report from the Intergovernmental Panel on Climate Change put it, the collapse of this ice sheet would be “irreversible for decades to millennia.”
“We were no longer even situated near the beginning of time. We were, in some ways, merely creatures living among the stars and just one part of a long planetary history.”
The thawing permafrost scenario, which would release billions of tonnes of methane into the skies, is also likely already underway. And again, this sudden ejection of stored greenhouse gas would be, according to another report from the Intergovernmental Panel on Climate Change, “irreversible on time scales relevant to human societies.”
This reference to future timescales, well beyond our lifetimes, brings us to the third and final issue of time — and the hardest to wrap our minds around. When the PETM started, it took 5,000 to 10,000 years to stuff the atmosphere with vast plumes of carbon dioxide. Bloated with CO2, the atmosphere then took more than 150,000 years to return to pre-PETM levels. Once saturated in the atmosphere, it takes a long time to naturally sequester the molecule. “Most people are not aware of this,” says Zeebe. And for Wing, this was the biggest lesson he wanted people to draw from the PETM: the understanding that the impacts of our actions now will last millennia. To return carbon dioxide to pre-industrial levels — from 419 to 270 parts per million — could take as long as 10,000 years. “For human purposes,” Wing told me, “it might as well be permanent.” For a species that thinks in election cycles, this is hard to grapple with.
It’s for this reason, climate scientists warn, we must urgently lower emissions to prevent us from going over at most 2 C of warming. That’s non-negotiable, and we’ve already wasted precious time. But consider- ing that the CO2 already jammed into the atmosphere will be with us for a longer time — for thousands of years, even if we went to net-zero emissions today — many think we need to act with equal urgency to adapt. Protecting against the devastating droughts and rising seas, especially in countries lacking protective infrastructure, is increasingly critical. And so is, a growing chorus of experts say, the need for technologies like direct air capture: machines that suck carbon dioxide directly from the air and store it deep within the Earth or use it to create usable products like fuel. Ten years ago, most would have thought direct air capture was a “moral hazard,” taking attention away from things we can do now to lower emissions, like renewable power and electrification. But Wing believes time has already run out, and perceptions are shifting.
“We’ve gone from worrying about moral hazards,” Wing says, “to worrying about how the hell do we limit the amount of damage.”
Our atmosphere takes on roughly an additional two parts per million of CO2 every year. If we can get our acts together, thousands of years from now our descendents might, after cursing us for getting them into this mess, grudgingly thank us for the (relatively) early efforts to limit the fallout.
Imprints of ancient life, glimpsed among our modern structures, are reminders of the deep time of life on Earth. (Photo: Ben Powless/Can Geo)
Pouring a cup of coffee in the morning, the steam swirling off the black, liquid surface, I rarely think about the long expanse of geologic time, despite inhabiting a world chock-full of reminders. I rarely let my mind wander to the Ottawa River, where Carleton and I saw the stromatolite fossils, those oxygen-producing powerhouses, etched in rocks like giant circular cells. Or to the Bighorn Basin, where PETM creatures lived in a dryer, hotter climate. Or even to the countless other fossils below my feet, these traces of Earth’s prehistoric past. Instead, I’m preoccupied with my daily to-do list and already anticipating my second coffee.
That’s why we have paleoclimatologists. While we think in days, weeks and years, they think in epochs. Through rocks, fossils and sediments, they study the slow march of time and the equally slow evolution of species and climates. Climate change, which is altering our biosphere in hundreds of years, is alarming to paleoclimatologists like Zeebe and Wing who normally observe these changes in thousands or millions of years.
Wing, who speaks with an impassioned yet methodical cadence, shares how his research of deep time gave him a new philosophic perspective. Near the end of our conversation, he reflected on the larger impact of scientific thought. How, since Galileo, humans had discovered their true insignificance: we were not the centre of the solar system. Because of Darwin, we were no longer even situated near the beginning of time. We were, in some ways, merely creatures living among the stars and just one part of a long planetary history.
But Wing has had to rethink that notion. “Now, all that is true,” he tells me, “but what our technological society is capable of doing is profound on a planetary scale. The effects will last for geologic time.” If paleoclimatologists were to study our current moment millions of years down the road, the fingerprints of our actions would show up everywhere. The chemicals leached into the ground, the layers of non-biodegradable garbage, the spike of countless species killed from climate change and industrialization. If the Paleocene-Eocene was a monumental event, so too is what many describe as the Anthropocene — a human-shaped epoch underway today. The point being: we may not be the centre of the universe, but we are not insignificant. “That is a pretty profound shift in how we think about ourselves.”