The Weekend Wonk: PETM – the Fire Last Time

August 28, 2016

Useful 2014 Lecture above, reposting some info on this below.

PETM, the Paleocene – Eocene Thermal Maximum.

That’s the last time in earth history that things changed in a way similar to the way they are changing now. It was 55 million years ago, give or take a millenium.

Scientific American (sub required – you can also buy single issues) has an article by one of the real experts, Lee Kump, comparing the pace at which the earth changed during the most recent Great Warming event.  As the sobering graph shows, the current CO2 buildup is prodeeding at a blistering pace compared to the ancient past.  Current rates of change are thousands of times faster than normal, and even 10 times faster than one of the most spectacular geological changes in the record.

The PETM bears some striking resemblances to the human-caused climate change unfolding today. Most notably, the culprit
behind it was a massive injection of heat-trapping greenhousegases into the atmosphere and oceans, comparable in volume to
what our persistent burning of fossil fuels could deliver in coming centuries….. New answers provide sobering clarity. They suggest the consequences of the planet’s last great globalwarming paled in comparison to what lies ahead, and they add new support for predictions thathumanity will suffer if our course remains unaltered.

The PETM had a big impact on life in the oceans, as evidenced by this sediment core.

According to Kump:

..Today investigators think the PETM unfolded something like this: As is true of our current climate crisis, the PETM began, in a sense, with the burning of fossil fuels.

At the time the supercontinent Pangaea was in the final stages of breaking up, and the earth’s crust was ripping apart, forming the northeastern Atlantic Ocean.

As a result, huge volumes of molten rock and intense heat rose up through the landmass that encompassed Europe and Greenland, baking carbon-rich sediments and perhaps even some coal and oil near the surface. The baking sediments, in turn, released large doses of two strong greenhouse gases, carbon dioxide and methane.

Judging by the enormous volume of the eruptions, the volcanoes probably accounted for an initial buildup of greenhouse gases on the order of a few hundred petagrams of carbon, enough to raise global temperature by a couple of degrees. But most analyses, including ours, suggest it took something more to propel the PETM to its hottest point.

When the gas releases began, the oceans absorbed much of the CO2 (and the methane later converted to CO2). This natural carbon sequestration helped to offset warming at first. Eventually, though, so much of the gas seeped into the deep ocean that it created a surplus of carbonic acid, a process known as acidification.

Moreover, as the deep sea warmed, its oxygen content dwindled(warmer water cannot hold as much of this life-sustaininggas as cold water can). These changes spelled disaster for certain microscopic organisms called foraminifera, which lived on the sea floor and within its sediments. (the whitish colored sediment at the bottom of the core here – PS) The fossil record reveals their inability to cope: 30 to 50 percent of those species went extinct.

The message of the graph, and the core, are clear. We are changing the planet at a rate unprecedented outside of the most severe convulsions the planet has seen in 4 billion years of history. We do not know what the results will be.
I don’t think I want my children and grandchildren to find out.

In the video below, James Hansen’s abbreviated lecture on paleo-history since the PETM.



4 Responses to “The Weekend Wonk: PETM – the Fire Last Time”

  1. mbrysonb Says:

    A word to the wise is sufficient… I wish I knew what would suffice to get an adequate response to this threat underway.

  2. I think information like what is presented in this post scares the shit out of people, which causes them to retreat into a state of tactical ignoring. It represents a Big Picture that the layman terms as “out of his control,” and that since the event does not really affect society now, why really worry about it? They think, “There will surely be a solution, right?”

    So, it becomes easier to get worked up with the easier current events of the day such as arguing over the election, or other short term issues. Folks retreat into their respective camps to commiserate and pass around a plate heaped full of confirmation bias.

    I shared this article on both my Facebook profile and my FB “group.” Out of 225 “friends” I’ll probably get a few “likes,” and even less comments. Yet, yesterday, I posted some good personal news on my FB profile and at this time I have received a slew of likes and comments. It’s just the way the human mind works, and is one of the reasons why I suspect we won’t dig our way out of this mess of our own making; but will rather keep digging ourselves deeper.

  3. Scarier analogy, at least on the rate of CO2 injection: ( Ogden, Sleep,
    “Explosive eruption of coal and basalt and the end-Permian mass extinction”.

    Dr Neil deGrasse Tyson dramatized this even in his COSMOS episode, “The lost worlds of planet Earth” (

    While the pace of introduction of CO2 into atmosphere was apparently comparable to today, in the end-Permian this CO2 was lofted high into top-of-troposphere and stratosphere due to rising heat columns from the Large Igneous Province (LIP) that was producing it by burning through coal beds. Most of our CO2 is emitted near the Earth surface, with the exception of aircraft which do emit high in atmosphere. This is why, per mass unit, the CO2 from aircraft make a much larger contribution to forcing than does the same mass unit at Sea Level.

    The thing that bothers me, as a dynamicist, and some others is wrapped up in your observation “As the sobering graph shows, the current CO2 buildup is proceeding at a blistering pace compared to the ancient past.” We don’t know what effects a large time derivative of forcing might have. At geological scales, it surely LOOKS like an impulse, and, if the climate system were predominantly linear, we’d see an impulse response and that’s all. But it’s far from that kind of linear, and we don’t know if there are bifurcations in its state space. Some of these could be directly interpretable, such as the shutting down or reversal of the AMOC. But others could be latent. These possibilities have been examined in part:

    And it seems if such a thing were about to happen, the changes might be quite subtle:

    I have made some additional remarks about this here:

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