In the Blink of an Eye, We’re Turning Back the Climatic Clock by 50 Million Years

By Tom Yulsman | December 14, 2018 3:45 pm
This animation based on computer modeling shows what climatic conditions will look like out to the year 2280 if we emissions of greenhouse gases are not restrained. The color coding shows how future conditions would compare to climates of the past. (Source: "Pliocene and Eocene provide best analogs for near-future climates," K. D. Burke et al, Proceedings of the National Academy of Sciences Dec 2018, 201809600; DOI: 10.1073/pnas.1809600115)

This animation depicts climatic conditions out to 2280 assuming emissions of greenhouse gases are not restrained. The color coding shows how future conditions would compare to past climates, with lighter orange corresponding to the Pliocene Epoch about 3 million years ago, and darker orange to the Eocene about 50 million years ago. Dark red indicates future climatic conditions with no past analog. (Source: “Pliocene and Eocene provide best analogs for near-future climates,” K. D. Burke et al, Proceedings of the National Academy of Sciences Dec 2018, 2018)

Absent serious action on climate change, we’ll continue careening toward a climatic cliff. And modern civilization will be hard-pressed to survive the plunge.

This is the essential take-away from new research probing Earth’s climatic past to yield insights into our future. The research finds that if our emissions of carbon dioxide and other greenhouse gases continue unabated, Earth’s climate will warm by the year 2150 to levels not seen since the largely ice-free Eocene Epoch about 50 million years ago.

That may seem like a long time on a human timescale. But consider that the research shows we’re currently on course to reversing 50 million years of cooling in just a couple of centuries. That may be so rapid that it will outpace our ability to adapt our agricultural and other modern life support systems.

Thanks to our emissions of greenhouse gases, “the Earth system is well along on a trajectory to a climate state different from any experienced in our history of agricultural civilizations,” write Kevin Burke and his co-authors in a paper published in the Proceedings of the National Academy of Sciences.

Here’s why that’s troubling: Modern human civilizations, made possible by agriculture, have thrived in what scientists term “a safe operating space,” meaning a stable, relatively benign climate. But now, staying within that safe space seems to be “increasingly unlikely,” the researchers write.

“If we think about the future in terms of the past, where we are going is uncharted territory for human society,” says the study’s lead author, Kevin Burke, in a press release. Burke led the research while he was a graduate student in the lab of paleoecologist John “Jack” Williams of the University of Wisconsin-Madison.

“We are moving toward very dramatic changes over an extremely rapid time frame, reversing a planetary cooling trend in a matter of centuries,” Burke says.

Temperature trends for the past 65 million years and potential geohistorical analogs for future climates. Red arrows show six geohistorical states of the climate system: Paleocene, Miocene, Oligocene, TK, TK and TK. A time series showing global mean annual temperatures is also shown. Major patterns include a long-term cooling trend, periodic fluctuations driven by changes in the Earth’s orbit, and recent and projected warming trends. Temperature anomalies are relative to 1961–1990 global means. (Source: TKTK

Temperature trends for the past 65 million years and potential past analogs for future climates. Red arrows show  “geohistorical” states of the climate system. From the left, these are the early Eocene Epoch; the mid-Pliocene; the last interglacial, or LIG; the mid-Holocene; the pre-industrial period; the historical period; and projections for the future (at extreme right). The time series shows how global mean annual temperatures departed from the 1961 to 1990 mean. Major patterns include a 50-million-year cooling trend beginning in the Eocene, periodic fluctuations driven by changes in the Earth’s orbit, the recent warming caused by human activities, and projected warming. (Source: “Pliocene and Eocene provide best analogs for near-future climates,” K. D. Burke et al, Proceedings of the National Academy of Sciences Dec 2018, 2018)

To conduct the research, Burke and his colleagues compared climatic conditions of several periods in geologic history with computer model projections of the future. These projections assumed different greenhouse gas emission scenarios.

One sobering finding was that we are already headed toward a climatic state like that of the mid-Pliocene Epoch about 3 million years ago even if we do manage to reduce our emissions of greenhouse gases. In fact, thanks to burning of fossil fuels and other human activities, carbon dioxide concentrations in the atmosphere are already at Pliocene levels: more than 400 parts per million. We just don’t have a Pliocene-like climate yet because most of the planet’s surface is covered in oceans — and all that water takes time to warm up.

The research shows that if we undertake moderate emissions reductions, we’ll stabilize at Pliocene-like temperatures by 2040. During the Pliocene, temperatures were between 3.2 and 6.5 degrees Fahrenheit (1.8 to 3.6 degrees Celsius) warmer than they are today.

At their peak, sea level during the Pliocene stood 72 feet (22 meters) higher than today. Luckily, inertia in the climate system means that it would take a few centuries before sea level would come up to that level again. (Looking at past climates, scientists have documented maximum rates of sea level rise of three to five meters per century.)

Even so, Pliocene-like temperatures should bring a host of climate impacts that will prove challenging for modern societies to adapt to. And over time, we’ll have to deal with that Pliocene-like sea level rise.

“There is a very good relationship between sea level and temperature on the planet,” says James White, a paleoclimatologist at the University of Colorado who was not involved in the current research. “If you warm up air, and you warm up water, you melt ice. And when land ice melts and goes into the ocean, you raise sea level.”

The 20 meters of sea level rise that correspond to a Pliocene-like climate “is enormous,” White says. It would submerge coastal cities around the globe which are currently home to many tens of millions of human beings.

The silver lining is that by reducing carbon emissions, we’d at least stabilize climatically without things getting even more challenging. But if we don’t reduce our emissions, the planet will continue to warm — quite dramatically.

By the year 2150, Earth’s average temperature would rise by a staggering 23 degrees Fahrenheit (13 degrees Celsius) above current conditions, taking them to Eocene-like levels. During that geologic epoch, there was no permanent ice on the planet, and sea level is estimated to have been at least 100 meters higher than today.

If we follow this path, the rapid change we’d trigger would be without precedent during the entire Cenozoic Era, the age of mammals, which began about 65 million years ago when the dinosaurs went extinct.

“What the planet’s going to do is very predictable,” White observes. Basic physics plus research on past climatic states provides confidence that “temperatures will rise, sea level will go up, and storms will get worse. It’s all very predictable. What’s not is how we will respond.”

I don’t know about you, but I’d prefer to respond in a way that would leave us in the Pliocene, not the Eocene.

  • Mike Richardson

    This milestone would be reached during the lifetime of any potential grandchildren, or at least great grandchildren, I might have. A bit of a ways off for most folks alive now, but certainly an extremely rapid change in geological time. However, generations currently alive will be seeing some pretty severe disruptions long before 2150, and could potentially experience the end of civilization before we reach that threshold. The window for meaningful action to mitigate the most severe impacts of climate change is clearly closing. Whether out of concern for our descendants, or even ourselves, humanity needs to treat this growing crisis with the urgency it deserves.

    • Tom Yulsman

      And as urgently as we need to mitigate emissions, we also have to focus on adapting to changes already underway, and changes that will soon leave us in a Pliocene-like state. But for some reason, mainstream news outlets like the New York Times insist on covering climate change as a simplistic ‘good guys versus bad guys’ political story focusing only on one dimension: mitigation of greenhouse gas emissions. Yes, of course, we have to do that, and in a very big way. But we’re ignoring an equally important part of our long-term response to climate change.

  • A J

    The hyperbole both sides of this debate exhibit is a fear tactic and factually inaccurate. The end of civilization??? Not likely.

  • James Swanson

    What do you think about it? Are we able to change that? Or we should just accept it?

  • John C

    Absent serious action on climate change…


    For starters:

    1. Convince billions of people in India and China to give up coal, and thus seriously downgrade their personal economic expectations.

    2. Build a huge number of latest generation nuclear power plants, ignoring fierce political opposition from greens.

    3. Closer to home, add 10,000 sq. miles (larger than the area of Vermont) of solar panels to the U.S. grid to replace carbon power generation.

    4. Exponentially expand and upgrade the U.S. power grid to handle #3.

    5. Everybody on Earth hold their breath for a year.

    They’re all about as easy to do.

    Climate change falls into the category of a “wicked hard problem”, like fixing poverty or war. It is of such staggering complexity and scale that we can only hope for an approximate solution, as with poverty or war.

    • With Respect

      1. New renewables are cheaper than new coal, including in India and China (both of which outspend other nations on renewable R&D). Economic wellbeing is fully decoupled from coal, or any fossil fume emitter, except insofar as downside smog, climate change, affects on ecosystems overall impact economics.

      2. New renewables are much cheaper than nuclear. The standard for nuclear among safety experts is ALARA — As Low As Reasonably Achievable. Fully deploy all renewable options, find those nuclear opportunities that are tenable, and resolve nuclear’s appalling waste disposal issues, and you have a case. Blaming ‘greens’ for the problems inherent in the business case for nuclear? Just absurd.

      3. Your numbers are dated. It’s ~7,500 square miles, or roughly 600 square feet per person, if you go pure solar, most of which can fit on rooftops or deserts. That can be cut in half to 300 square feet per person if you add wind power, which has a tiny footprint. Cut that in half again if you expand hydroelectric and geothermal electric. All of which is cheaper than any form of fossil. And then there’s offshore wind.

      4. Renewables make grids less expensive, not more expensive, due to the duck curve, if you upgrade to inexpensive ultra high voltage DC and take advantage of the best solar and wind peaking in the west just as the east’s demand peaks. Add some storage, and you make the grid more reliable overall, and far cheaper.

      Your firehose of fossil falsehood is transparent excuse to keep dumping wastes without paying for their disposal.

  • Christopher Johnson

    The one thing we know for sure: climatologists as a group are for more enamored of the “solution” than they are alarmed about the “problem”.



ImaGeo is a visual blog focusing on the intersection of imagery, imagination and Earth. It focuses on spectacular visuals related to the science of our planet, with an emphasis (although not an exclusive one) on the unfolding Anthropocene Epoch.

About Tom Yulsman

Tom Yulsman is Director of the Center for Environmental Journalism and a Professor of Journalism at the University of Colorado, Boulder. He also continues to work as a science and environmental journalist with more than 30 years of experience producing content for major publications. His work has appeared in the New York Times, Washington Post, Audubon, Climate Central, Columbia Journalism Review, Discover, Nieman Reports, and many other publications. He has held a variety of editorial positions over the years, including a stint as editor-in-chief of Earth magazine. Yulsman has written one book: Origins: the Quest for Our Cosmic Roots, published by the Institute of Physics in 2003.


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