They were strange days at the beginning of the age of mammals.
There are also polar bears, but Eberle luckily hasn't had any run-ins so far-though perspective can play tricks on you at the top of the world, and a snow-white artic hare on its hind legs at the appropriate distance can appear threatening enough.
The planet was still hungover from the astonishing disappearance of its marquee superstars, the dinosaurs.
And when the earth system finally does arrive at its equilibrium, it will most likely be in a climate state with no analog in the short evolutionary history of Homo sapiens.
And the temperatures they unearthed are unsurprisingly scorching.
On the other side of the blue-green orb, in waters that today would surround Antarctica, sea-surface temperatures might have topped an unthinkable 86 degrees Fahrenheit, with near-tropical forests on Antarctica itself.
To see exactly how hot, Naafs' team also analyzed ancient lignite samples from India, which would have been in the tropics at the time-that subcontinent still drifting across the Indian Ocean toward its eventual mountain-raising rendezvous with Asia.
“You put more CO2 in the atmosphere and you get more warming, that's just super-simple physics that we figured out in the 19th century,” says David Naafs, an organic geochemist at the University of Bristol.
And though the gulf is narrowing, and models are catching up, even those that come close to reproducing the hothouse of the early Eocene require injecting 16 times the modern level of CO2 into the air to achieve it-far beyond the rather meager doubling or tripling of CO2 indicated by the rock record.
And we know methane can actually amplify high-latitude warming, so maybe that's some of the missing feedback.”
Earth's newest crater was still a smoldering system of hydrothermal vents, roiling under the Gulf of Mexico.
In the wake of Armageddon our shell-shocked ancestors meekly negotiated new roles on a planet they inherited quite by accident.
Before long, life settled into new rhythms: Earth hosted 50-foot-long boas sliding through steam-bath jungles, birds grew gigantic in imitation of their dearly departed cousins, and mildly modern mammals we might squint to recognize appeared.
Naafs' team studied examples of lower-quality coals called lignites, or fossilized peat.
That should be mildly concerning.
There were perhaps even sprawling, febrile dead zones spanning the tropics, too hot even for animal or plant life of any sort.
And yet, there is a seeming disconnect, between traditional projections for future warming-like those made by the International Panel on Climate Change (IPCC), which predicts around 4 degrees Celsius (7 degrees Fahrenheit) of warming by the end of the century under a business-as-usual emissions scenario (still frightening) and sea-level rise measured in mere inches (still frightening)-and the scarcely recognizable Earths buried in the rocks and created under similar CO2regimes, like those that Eberle unearths.
yet at equilibrium for a 400-ppm world.
The changes that we've already set in motion, unless we act rapidly to countervail them, will similarly take millennia to fully unfold.
The last time CO2 was at 400 ppm (as it is today) was 3 million years ago during the Pliocene epoch, when sea levels were perhaps 80 feet higher than today.
And they are around 50 million years old.
The continents were in slightly different positions, leading to a vastly different ocean circulation and boundary conditions quite unlike our own world, 50 million years on-with all the tectonic, oceanographic, and biological changes that come with such a yawning expanse of time.
But over 50 million years ago this would have been the baseline from about 45 to 60 degrees latitude.
Most worryingly, the climate models that we depend on as a species to predict our future have largely failed to predict our sultry ancient past.
Naafs' work fits into a larger developing picture of Earth as an almost unrecognizable greenhouse planet of the distant past.
Ellesmere is as far north as you can get before you fall off North America and run into Pere Noel drifting over pack ice.
Her target is warmer-weather fauna.
We have to be careful when making comparisons between the two.
“Some climate models suggest that the tropics just became a dead zone with temperatures over 50 degrees Celsius (122 degrees Fahrenheit) like in Africa and South America,” says Naafs.
“We know the hotter it gets the more methane comes out of these wetlands, but we know nothing about the methane cycle beyond the reach of ice cores which only goes back 800,000 years...
“These wetlands looked exactly how only tropical wetlands look at present, like the Everglades or the Amazon,” Naafs says.
If we do, in fact, push CO2 up to around 1,000 ppm by the end of the century, the warming will persist and the earth will continue to change for what, to humans, is a practical eternity.
To study Earth's past, scientists need good rocks to study, and fortunately for geologists and fossil-fuel companies alike, the jungles and swamps of this early age of mammals left behind lots of coal.
They were able to reverse engineer the ancient climate by analyzing temperature-sensitive structures of lipids produced by fossil bacteria and archaea living in these bygone wetlands, and preserved for all time in the coal.
Within a few million years, loosed from under the iron heel of the vanished giants, they began to experiment.
That is, they were too hot for his team to measure by the new methods they had developed.
And it won't be for quite some time.
“So Europe would look like the Everglades and a heat wave like we're currently experiencing in Europe would be completely normal.
We don't know.” So that was life in the late Paleocene and early Eocene in the high mid-latitudes.
The Powder River Basin in the United States, for instance, is filled with fossil Paleocene swamplands that, when burned today, contribute about 10 percent of U.S. carbon emissions.
“If we were to burn all the fossil fuels and wait a few centuries we might return to this,” he says.
“The fossil forests on Ellesmere are spectacular,” Eberle says about the ecosystem entombed in the arctic soils.
But unfortunately, the temperatures from these samples were maxed out.
You have tapirs-so you've got tapirs living pretty close to the North Pole in the early Eocene, which today-clearly tapirs are not at the North Pole,” she says, laughing.
Clearly we are missing something, and Naafs thinks that one of the missing ingredients in the models is methane, a powerful greenhouse gas which might help close the divide between model worlds and fossil worlds.
“Basically every type of paleoclimate research that's being done shows that high CO2 means that it's very warm.
“You've got alligators, giant tortoises, primates, things like that.
Here, featureless highlands overlook ice-choked fjords and a lone Peary's caribou might mingle with a dozen musk oxen under a vast Nunavut sky.
“You start really looking into them and you go, ‘Wow.
That modern European heat wave has, in recent weeks, sent sunbathing Scandinavians and reindeer to the beach in temperatures topping 90 degrees Fahrenheit in the Arctic Circle.
