The Last Time the Globe Warmed

Thanks to Curiosity Stream for supporting
PBS Digital Studios. Imagine an enormous rainforest teeming with
life: trees, insects, pretty little birds. Primates are climbing in the canopy, while
crocodiles and turtles swim in the rivers below. Beautiful, isn’t it? Now imagine this lush rainforest … in the
Arctic. There was a time — and not too long ago — when
the world warmed more than any human has ever seen. So far. This ancient warming took place over the course
of just 200,000 years — the blink of an eye in geologic time — and it ended much like
it began: suddenly and mysteriously. It all started 56 million years ago, at the
very end of the Paleocene Epoch. Back then, life was still recovering from
the unpleasantness of the Cretaceous-Paleogene extinction event, which wiped out the non-avian
dinosaurs. And things were already warm by today’s
standards. There were no polar ice caps, which meant
sea levels were much higher. And the continents — which were just beginning
to take a familiar shape — were covered in habitats like temperate forests, and deserts,
and a belt of rainforests around the equator. But this environment was about to change. In fewer than 20 thousand years, the global
average temperature increased by 5 to 8 degrees Celsius. And the warming was greatest at higher latitudes. So, at the poles, temps on land reached an
average of 23 degrees, while the ocean waters got up to a balmy 20 degrees, This means you
could’ve gone for a comfy swim in the seas around Antarctica! This remarkable and sudden warming event is
known as the Paleocene-Eocene Thermal Maximum, or PETM, and it had a massive effect on
life on Earth. For one thing, when the PETM reached its peak,
rainforests had expanded much farther than they ever had before. Fossils from North America, Europe, and Asia
reveal habitats rich in plant life that today are associated with tropical rainforests
— even though these forests were nowhere near the tropics. The fossilized fronds of palm trees have been
found as far north as Wyoming, for example. And some places within the Arctic Circle,
like Ellesmere Island in Canada, show evidence of ferns, redwoods, and gingkos. So. How was all of this — any of this — possible? Our best clues can be found in ancient sediments. Marine sediment samples from Maryland to Antarctica
show that, about 56 million years ago, there was a sudden spike in the amount of carbon
dioxide and other greenhouse gases in the oceans. And judging by the types of carbon found in
these sediments, the gases likely came from organic matter, like plants. See, plants, like most living things, prefer
to use the lighter and more common isotope of carbon, carbon-12, as opposed to heavier
isotopes, like carbon-13. So, this biogenic carbon — which we’ve
talked about before — has a different chemical signature than carbon that’s never been
part of a living organism. And, sediments that date to the start of the
PETM, show a large and sudden drop in the ratio of carbon-13, compared to carbon-12. This means that a bunch of biogenic carbon
must have suddenly been released into the atmosphere, in the form of carbon dioxide,
methane, and other gases. But, where did these gases come from? Well, one hypothesis is that there was a rash
of massive wildfires that unleashed tons of CO2 that had been locked up in plants. Another model proposes that giant seams of
coal were exposed to the heat of volcanic activity, which would have released the carbon
from fossilized plants. Or it could be that an otherwise mild warming
event triggered the release of greenhouse gases, by melting deposits of a compound known
as methane hydrate. Methane hydrate is similar to ice, but it
contains molecules of methane trapped by molecules of water. And hydrates are usually stable, as long as
they’re under a lot of pressure, like deep in the oceans, or if they’re kept cold,
like in permafrost — the thick layer of frozen soil that forms in cold climates. But if these places warm up, the hydrates
melt, releasing bursts of methane, which is an even more potent greenhouse gas than CO2. And of course, the more warming that happens,
the more melting there is, which releases even more greenhouses gases, creating a classic
positive feedback loop. Now, no matter how it started, it’s worth
noting that, during the PETM, carbon was released into the atmosphere at only a fraction of
the rate at which it’s being emitted today. One study of marine sediments from the Arctic
showed that, at the peak of the PETM, as much as 1.7 billion metric tons of carbon were
released into the atmosphere every year, for at least 4,000 years. A similar study of sediments from New Jersey
put the figure at about 1.1 billion tons of carbon every year. Now, compare that to the amount of carbon
being released today. In 2014 alone, it was 9.8 billion metric tons
of carbon. So, 56 million years ago, carbon was being
released less quickly than it is now, but those emissions continued for thousands of
years. And it was more than enough to create a potent
greenhouse effect. With more carbon in the atmosphere than plants
could absorb, the planet started to change rapidly. In many places, the climate delivered a combination
of humidity and heat that allowed vast rainforests to flourish. And among the animals that thrived in these
warm forests were reptiles. Fossils of alligators, crocodiles, and turtles
can be found in nearly every fossil bed from the PETM — even in the polar forests of Canada
and Greenland. And these lush forests were also where many
early mammal groups diversified — including our every own lineage, the primates. In fact, the earliest true primates appear
in the fossil record just as the PETM was starting to take off, 56 million years ago. They adapted quickly to a world covered in trees, developing things like forward-facing eyes, fingernails instead of claws, and opposable
thumbs. These features gave primates such an edge,
that by 53 million years ago, they could be found across the northern hemisphere — from
tiny Eosimias in China to Notharctus in Wyoming. But in the oceans, life in hothouse Earth
became much harder. In fact, in some places it was almost impossible. At the equator, ocean temperatures were unbearably
hot, sometimes reaching as high as 36 degrees, almost as hot as your average hot tub. This was probably too hot for many kinds of
plankton, which were — and are — the basis for most ocean food webs. But an even more devastating side effect of
high CO2 levels was ocean acidification. When ocean water absorbs CO2, it becomes more
acidic. And this in turn depletes the water’s concentration
of carbonates — the compounds that many organisms use to build shells and other structures. And this is why one of the clearest effects
of the thermal maximum can still be found in core samples from the deep sea. Sediments that date back to before the warming
are typically pale in color, because they’re rich with the skeletons of deep sea foraminifera. Also known as forams, these are tiny protozoans
that build shells of calcium carbonate. And where forams were abundant, the chalky
fossils of their shells turned the ocean bed white. But when the oceans became more acidic, the
sediments turned dark. Because … most of the forams just disappeared. During the PETM, between 30 and 50 percent
of all foram species went extinct. The same phenomenon also stunted the growth
of hard corals, which need carbonates to build their skeletons, too. So, during the PETM and for millions of years
afterward, big, complex coral reefs all but disappeared from the fossil record. All told, the thermal maximum was a mixed bag
for life on Earth – proving to be an important period for us mammals, but a major loss for
some marine life. And, like all dramatic events, the PETM did
come to an end. Although, we’re not sure how, or
why. Over the course of the Eocene epoch, the climate
slowly began to cool. And although the temperature occasionally
spiked again, it never reached the extremes of the maximum. Temperatures kept dropping during the Eocene
— so much so, in fact, that by the end of the epoch, 34 million years ago, polar ice
caps had begun to form. But, how did we get from rainforests near
the poles to ice caps? Well, the cause of the initial cooling that
actually stopped the PETM 53 million years ago remains a mystery. But something allowed that cooling to take
hold, and make the world even colder. And the answer here might have to do, again,
with plants. Arctic sediments that date back to the early Eocene
— 49 million years ago — have been found to contain huge swaths of fossilized aquatic
ferns known as Azolla. These plants thrived in the lush, warm Arctic. But as the environment changed, they died
off. And as they dropped to the seafloor, the thinking
goes, they took tons of carbon with them, which caused temperatures to drop even further. Despite how little we know about its end,
or its beginning, the Paleocene-Eocene Thermal Maximum shows us just how polarizing climate
change can be for life on Earth. For some organisms, like early primates, the
warming was a chance to develop new forms and spread to new locations. But for corals, forams, and other marine life,
such extreme heat spelled disaster. It gives us, in the midst of our own period
of warming, a view of how extreme the effects of climate change can be. And it allows us to make some pretty striking
comparisons. Remember when I said that, during the PETM,
the globe warmed more than humans had seen so far? Well, keep in mind that, in recent years,
the rate of annual carbon emissions have been more than five times greater than they were
at the peak of the PETM. As a result, our world is warming faster
than it did back in the Eocene. Just over the past hundred years, the average
global temperature has increased by about 0.7 degrees Celsius. But that’s just been over the past century. During the PETM, it took perhaps thousands
of years for temperatures to rise that much. So the PETM is the closest we can get to understanding
the effects of global warming today. And it has a lot to teach us about the extremes
that life experienced, on land and in the seas. Yes, rainforests full of primates and insects
and reptiles is beautiful. But I think you’ll agree with me that most
of us like them right where they are today. PBS Digital Studios is sponsored by Curiosity
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100 thoughts on “The Last Time the Globe Warmed”

  1. If you ever needed proof that we are in for a rough ride over the next few thousand years this is it. I don't think that there will be as many of us alive in say 1000 years as there is now.

  2. The last time the globe warmed, about 10,000 years ago, the ice age entered the temporary comfortable period in which we live. (PS, that's right, we're still living in that ice age)

  3. So.. currently we are on course for most life forms – including our own – to die off, but the planet will eventually regenerate with new life forms developing over the next few million years….. Reassuring. thanks.

  4. all this says to me is that man isnt the cause of global warming,nature it's self is and it isnt going to effect the world in 12 years if it takes 200,000 years to warm 8 degrees,coral reefs did not end,maybe your not heard of the great barrier reef in australia ? it's a beautiful coral reef

  5. RIght. And man had nothing to do with it then and nothing to do with it now. The push to do "something" is made by the globalist left who want to control each and every aspect of our lives. The global warming scam is the biggest fraud of all time with its current moronic bartender head honcho advocate the donkey toothed imbecile Cortez.

  6. So, by implication we should all panic and pay the extra 'green', taxes our western governments are fausting on us?
    That's a nope.

  7. Here's what we need, and a lot of it : Thorium based nuclear reactors. Thorium of course, are even more abundant than uranium. Thorium reactors are cleaner, and best of all, can't melt down.
    In fact, Roosevelt & Co should've chosen it when they could've, instead of going the weaponisable uranium route. But of course, he served the needs of his M.I. Complex puppet masters.

  8. what about 100 yrs ago when you could sail across the north pole because of lack of ice. the real climate scientists not only disagree with your so-called facts ,they predict a major cooling trend coming soon. for me i like to be warm. i love the global warming, not to big on the global cooling and much less on the coming ice age ,eeeuuuwww Brrrr very nippy ,nipply

  9. Interesting to note; you don’t even consider Sun activity or the Earths trajectory round the Sun nor the Earths tilt or the Moons trajectory or its distance from Earth. All these factors change over time and as you have made the point of not including these various other factors, I can’t take you seriously. Sorry but you are giving only half a story.

  10. Humans are a temporary factor of the planets history. The planet will eliminate all humans and go on a few more billion years. It makes me laugh when I hear "save the planet", the planet is getting ready to flick us off like a bad case of fleas.

  11. Carbon and carbon dioxide are two completely different things. Shortening CO2 to Carbon. is wrong, and misleading. If this series is really serious about science, the two should never be used interchangeably.

  12. Obviously the true north is changing. It has changed around thirty miles recently. Some even that say the polar caps were once filled with tropical rain forests, this beg the question as to how much has the polar north changed over the last million years… Where were the polar caps when Antarctic was a tropical land mass… Just ask'un…

  13. Last time earth warmed was 200 000 years ago. What are you talking about? Last 400 000 years ago have been ice age after ice age. At the end of each ice age there have been warmings leading to interglacials, like the one we experience now. The interglacials, each about 10 000 years of duration, have consisted in warmings and coolings, warmings and coolings. Last cooling apart from the present one, took place in the middle ages. Not 200 000 yago. And surely not 54 million yago.

  14. No mention of the biggest climate change causer in the solar system – The Sun which is 99% of the system. Instead "we don't know why the planet cooled."

  15. So wait… The globe warmed, and humans had nothing to do with it? Color me shocked. It's almost as if the planet does it on its own…

  16. 99% of these comments: "I do not have a clear understanding of weather vs climate"
    1% of these comments: Trying to educate said 99% idiots

  17. During that time the CO2 levels were 1000 to 2000 PPM. This is very high compared to our 440 PPM of today AND even with it so high, life on Earth did NOT come to an end due to the high levels of CO2 and increased temperatures.

  18. LOTS more trees. Vastly fewer babies. East less meat. Stop driving gas hog cars. Stop using the ocean as a huge toilet. I'm sure people can think of more things that might help if WE ALL DID THEM.

  19. So, we only have a thousand years to reduce greenhouse gasses? This guy was espousing a theory, yet didn't say that directly, nor did he say it's a fact. Perhaps a well formed theory, but a theory, none the less.

  20. 'To suddenly label CO2 as a "pollutant" is a disservice to a gas that has played an enormous role in the development and sustainability of all life on this wonderful Earth. Mother Earth has clearly ruled that CO2 is not a pollutant.' (Robert Balling, as quoted by Popular Technology)

    Climate changes because of circulation patterns caused by Solar activity ( changes in irradiance, Magnet Field, absorption in the stratosphere, Cosmic rays modulation) and the stages of the moon. Man does not have the ability to change circulation patterns. Temperatures changes has nothing to do with CO2. You can not control CO2 (you breath out CO2 (40,000 ppm) plant food). CO2 can never be a air pollutant ( 2 USA supreme court judges) The weather Climate system is powered by solar energy. The Total solar irradiance (W/m2) (temperature) data matches very well with Northern Hemisphere temperatures. Compare Total solar irradiance (W/m2) vs Total Water Vapour matching very good. Climate has being changing for 4.5 billion years. Climate change is nothing that you have to prove, it is always changing. Making Climate change into something that is alarming, which governments are doing is weird and irresponsible and devious.

  21. carbon levels rise AFTER temperature rises. that's a yet unexplained fact nobody likes to talk about. (Al Gore fooled his audiences back then by omitting this fact)

  22. im actually for global warming, im sick of it being cold all the time. This is actually pretty exciting, i might be living the the tropics in 20 years

  23. no warming for nearly the last twenty years
    mass immigration to western countries and stifling of dissenting views throw PC language
    interference in farming practices making farming unviable in western countries the same farms being bought by chinese
    push to eliminate meat from western diets and replace with soy based protein, not great for male testerone and again those same beef producers being bought for chinese population
    the wholesale spread of socialism and the destruction of democracy and capitalism

  24. Where is the medieval warming period? Where is the 1930s? How much has the earth warmed in the past 15 years? Why did Michael Mann lose his defamation lawsuit in Canada against a TRUTH defense?

  25. The depictions of the weather in these climate shifts are always depicted as placid. Is that because the weather systems were benign or we have no idea how to predict how the earths weather would have been with subtropical polar regions? I think all that heat in the oceans would have produced very profound magnitudes in weather.

  26. So global warming is good then!…..we have been scammed, well some useful idiots have. If the sun doesn't go super nova soon we're all doomed, doomed I tell you doooooommmddddd.

  27. They forgot to preface this with the words 'we believe'. This is a theory, an educated guess.
    Hundreds of models with many differring explanations. They just took the data they liked and went with it.

  28. Finally, a documentary that notes life will not end when the earth warms! Sure, life will change, but that is called EVOLUTION. Surely you have heard about that. In fact if you paid attention, this documentary notes that primates developed and flourished when the earth was warmer. No, the earth will not be the same as it is today as Global warming takes effect. Yes, life is going to change. But that is the whole thing about life on earth – it changes. Life adapts to the environment it is in. Without adaptation, life would have ended right after it began. If you think that Humans are destine to rule the earth forever, you have failed history.

  29. Couldn't global warming be similar to how the stock market moves? If you look at it on a very short interval, it's volatile. You see quick spikes and dips. But if you look at it over a longer period of time, those spikes and dips even out, and the rises and falls appear to be slower. I wonder if maybe when we study the climate 50 million years ago if we're only able to see longer period trends rather than spikes and dips over short intervals of time. Maybe the reason it looks like the earth is warming so quickly right now is because we're only looking at a very short interval of time–the last 100 years. This could just be a quick spike that, if we looked at things over a longer period of time, would even out. Maybe spikes like this have been common in the past, but we can't know because we can only see things over larger intervals. I mean if there were little dramatic spikes and dips during the heating that happened 50 million years ago, would we be able to detect it?

  30. This bloke can't make up his mind, global warming was bad but primates thrived , CO2 is bad but trees thrived, water heated up -bad,yet i bet those animals living near ocean vents loved it. coral died, yet go to the ocean & coral is everywhere. So the world changed some died some lived, about the same as every era ever.

  31. And there wasn't a SINGLE HUMAN AROUND to cause it.
    The Climate is dynamic. Always has been and always will be.
    Anybody talking about "man-made climate change" is both a liar, and a RELIGIOUS FANATIC.

  32. " It remains a mystery", "it might have to do with plants", "in the last century the temperature rise by 0.7" , "no matter how it started" , hypothesis no: 1, 2, 3, …

  33. This guy needs to watch answer in genesis this world has been here for only about 4500 to 4700 years the flood was 4300 years ago the only thing you have to do is BELIEVE…..

  34. Moral of the story… Climate change is only an issue, if your looking out for the world of human to maintain control. Democrats are against PETA, ASPCA, and the Environment.. they just want the world to not go into global warming again – because the last tine (PETM) "humans" evolved. I say, "Lets try again – and hail our Lizard Overlords!"

  35. This is the time when primates started to evolve into beings that could live parasitically off their fellow primates by manipulating data, invoking misleading half-truths, and presenting gross assumptions as unquestionable realities.

  36. 9:15 Ok, if you're not bringing Volcanic Winters into this I wont even take you seriously. Had one in the 1816 and you mean to tell me that didnt cool the earth at all? 180,000,000,000 tons of material spewed then. Thats 180 trillion tons. You're talkin 9.8 billion tons today? LOL big freakin whoop.

  37. But can't we melt the ice caps just a little? I mean they don't need to be like tropical or anything, just temperate. It's ok if they freeze in winter.

    Just make them stop exporting so much extra cold in winter. They're like freaking batteries of bad weather.

  38. I'm suspicious of anybody that comes at me with a jackhammer presentation on any subject. Oh I get it, were not supposed to have time to think between auditory insults.

  39. Like he said the co2 back then came from a loss in plants so it could be easily compensated by a rising amount of plants which isn’t possible now as our co2 comes from fossil fuels

  40. Quick question. Why hasn't Africa tried irrigating inward from the ocean to re-green the continent? It would be construction on a massive scale, but just dig the ditches and get water flowing in from the ocean. #TheThingsIWonder

  41. In response to your bottom line at the end: It is immaterial whether or not we "like them right where they are today" (the flora and fauna of the Earth). The Earth's record proves that the flora and fauna will not do so, regardless of what we humans do to try to change it, just like it doesn't matter what we do with respect to our own mortality as individuals.

    As you imply in the video, the Earth has rarely had ice caps during its ~5 billion year existence and our ice caps will, once again, melt in the future. Nope–no polar bears either (which are all doing great, ATM, despite the alarmists cries that they are threatened).

    Your argument sounds great but it's obviously just a bunch of crap science brainwashing, once one takes the time to dig deeper into the question of climate change. You and your ilk don't actually know what caused the PETM (CO2 is the claimed perp) any more than you know what ended it (which you admit you don't know). Nope–CO2 never was the temperature control knob:

    You and your tyrannical masters are whipping people into a frenzy while they bark up the wrong tree so that you may deny them fundamental liberties and their pursuit of happiness. It's that simple.

  42. well you look smart you sound smart but my pappy also told me if it looks like a duck swims like a duck its probably a platypus

  43. In other words… the earth will continue to go on. Plants and animals come and go. Yet somehow, mankind thinks they can control the natural elements. If man can finally control earthquakes, tsunamis, wildfires, rain, floods, hurricanes, tornadoes, meteors, asteroids, comets, and the earths orbit, and even prevent war… I’ll finally be convinced that they’ll be able to control global warming.

  44. This isn't possible. Scientists have clearly told me my evil truck is responsible for the end of the world…oh and cow farts.. I almost forgot the cow farts.

  45. There are other interesting topics on long term cycles of Glaciation or Ice Age Formation. While not quick to explain, there are key variables that all need to align for all the conditions to be right for a sudden cooling of the Earth. I am referring to the following but there are other hypothesis that are related to other major and earlier periods in the Earth's history.

    Milankovitch said three factors determine how much solar radiation reaches the Earth: the eccentricity of the Earth’s orbit, the angle of the Earth’s axis and the wobbling of the Earth’s axis.
    These three factors undergo periodic changes in what are known as Milankovitch Cycles

    Check out this topic:

  46. I am willing to venture an unsubstantiated guess, a theory if you will, that the sudden end to the PETM may have something to do with a critical ambient temperature that was reached, not in the air, but in the soils or more easily the oceans.

    And we all know so much of plant life is governed by the bacteria and fungi in the Earth's soil. So if these organisms were let's say mesothermic, and had theoretically some upper maximum for their existence, and if that upper maximum was suddenly reached, could a large scale die off of a critical species or species" of cyanobacteria contribute to the end PETM or Eocene decline? Could it be as simple as a sudden and massive die off of blue green aquatic algae?

  47. Am I the only guy that is looking forward to the effects of global warming.  I'm sure the residents o Greenland will be happy when they can have agriculture once more.

  48. So the video takes us to the end of the period in which the CO2 is at unheard of high levels and that 'causes' the cooling trend indecated in the graphic? When are man made global warming advocates going to realize (if ever) that atmospheric CO2 follows, not leads, global warming? Plus zero explanation of warm poles, most likely from a very thick, dense atmosphere' circulation.

  49. ive seen ur videos on vlog brothers…how much does the UN pay u to push their climate change initiative…quit twisting science history

  50. Imagine if the earth periodically went through cycles of warm and cold, imagine if the sea rose and receded as a consequence of this, imagine if people had to adapt to this changing environment during thousands of years, imagine if the climate was beyond our control and we were at the mercy of the natural forces in the universe. Then global warming would seem more normal, and you would realize how insignificant you really are.
    For you climate hysterics, I should point out that the maximum sea level rise has been vastly underestimated. If the ice sheets near the poles melt, not only will the land there rise, but the land around the equator will sink, because the earth has a constant volume.

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