More Evidence for a Hot Ancient Earth

August 6, 2018

Actually not that ancient, geologically.

50 or so million years ago, things were pretty damn hot.  Problem is we are not sure why, as climate models have trouble reproducing the temperatures that rocks show prevailed at that time – so some kind of as-yet-not understood feedback may have been in play.  Methane? Possibly, but does that mean we are headed for that future?
Again, unclear.  Aradhna Tripati (above), and James Hansen (below) above walk thru the known unknowns.

The Atlantic:

But the most striking feature of this early age of mammals is that it was almost unbelievably hot, so hot that around 50 million years ago there were crocodiles, palm trees, and sand tiger sharks in the Arctic Circle. 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. There were perhaps even sprawling, febrile dead zones spanning the tropics, too hot even for animal or plant life of any sort.

This is what you get in an ancient atmosphere with around 1,000 parts per million (ppm) of carbon dioxide. If this number sounds familiar, 1,000 ppm of CO2 is around what humanity is on pace to reach by the end of this century. That should be mildly concerning.

“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. “But exactly how much it will warm by the end of the century, we don’t know. Based on our research of these ancient climates, though, it’s probably more than we thought.”

Last week, Naafs and colleagues released a study in Nature Geoscience that reconstructs temperatures on land during this ancient high-CO2 hothouse of the late Paleocene and early Eocene epochs—the sweltering launch to the age of mammals. And the temperatures they unearthed are unsurprisingly scorching.

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. 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. Naafs’ team studied examples of lower-quality coals called lignites, or fossilized peat. They had been collected around the world (everywhere from open-pit coal mines in Germany to outcrops in New Zealand), and spanned the late-Paleocene and early-Eocene epochs, from around 56 to 48 million years ago. 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. The team found that, under this past regime of high CO2, in the ancient U.K., Germany, and New Zealand, life endured mean annual temperatures of 2329 degrees Celsius (73–84 degrees Fahrenheit) or 10–15 degrees Celsius (18–27 degrees Fahrenheit) warmer than modern times.

“These wetlands looked exactly how only tropical wetlands look at present, like the Everglades or the Amazon,” Naafs says. “So Europe would look like the Everglades and a heat wave like we’re currently experiencing in Europe would be completely normal. That is, it would be the everyday climate.”

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. It has also ignited devastating wildfires across Greece and triggered an excruciating weekend for Spain and Portugal. But over 50 million years ago this would have been the baseline from about 45 to 60 degrees latitude. Under this broiling regime, with unprecedented heat as the norm, actual heat waves might have begun to take on an unearthly quality.

“Perhaps a heat wave in Europe would be something like 40 degrees Celsius (104 degrees Fahrenheit) for three weeks. We don’t know.” So that was life in the late Paleocene and early Eocene in the high mid-latitudes. But closer to the equator in this global sweat lodge, the heat might have been even more outrageous, shattering the limits of complex life. 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. But unfortunately, the temperatures from these samples were maxed out. That is, they were too hot for his team to measure by the new methods they had developed. So it remains an open question just how infernal the tropics became in these early days of our ancestors, but some computers tasked with recreating this planet spit out the stuff of science fiction.

“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. “But we have no data so we don’t know.”


3 Responses to “More Evidence for a Hot Ancient Earth”

  1. rhymeswithgoalie Says:

    50 million years ago it was so hot that India got distracted and rammed into Asia (and insurance didn’t cover it). The uplifted Himalayas accelerated the removal of CO2 from the atmosphere.

    (OK, some of us need mnemonics to keep track of geologic history.)

  2. I did my own little investigation. In the worst cse scenario in which humaity does nothing to reduce CO2-emissions we go to a 690 PPM of CO2 in the atmosphere. This scenario is still pretty near what we are doing at the moment. In a slightly different scenario, also with hardly any attempt to reduce the CO2-emissions we get to 590 ppm. See my ivestigation (Dutch only):

  3. Susan Anderson Says:

    I’m taking every chance to remind people of this villainous story (h/t Eli Rabbett).

    Lies, corruption, and endangering all our futures:

    “Fred Singer is the most unethical scientist, in my opinion, that I have ever met. I said so in the early 1990s, publicly, and I am still confident in the truth of this statement.”

    “retraction was coerced. It was required to stop the SLAPP suit brought against me by a conservative think-tank in Washington that wanted to keep Fred Singer in action.”

    “my wife was … terrorized by this lawsuit. We had three young children. I was a Harvard postdoc now needing to find a next academic posting. She was a graduate student at Harvard. … She was scared we could lose our house and all our assets. We new it would be a 2-3 year ordeal that would drain our resources and attention…. Defending for a year took an enormous amount of my time. That is the meanness and force of a SLAPP suit.”

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