Ancient climate change triggered warming that lasted thousands of years

Earth
A composite image of the Western hemisphere of the Earth. Credit: NASA

A rapid rise in temperature on ancient Earth triggered a climate response that may have prolonged the warming for many thousands of years, according to scientists.

Their study, published online in Nature Geoscience, provides new evidence of a feedback that could explain the long duration of the Paleocene-Eocene Thermal Maximum (PETM), which is considered the best analogue for modern climate change.

The findings also suggest that climate change today could have long-lasting impacts on global temperature even if humans are able to curb greenhouse gas emissions.

"We found evidence for a feedback that occurs with rapid warming that can release even more into the atmosphere," said Shelby Lyons, a doctoral student in geosciences at Penn State. "This feedback may have extended the PETM climate event for tens or hundreds of thousands of years. We hypothesize this is also something that could occur in the future."

Increased erosion during the PETM, approximately 56 million years ago, freed large amounts of fossil carbon stored in rocks and released enough carbon dioxide, a greenhouse gas, into the atmosphere to impact temperatures long term, researchers said.

Scientists found evidence for the massive carbon release in coastal sediment fossil cores. They analyzed the samples using an innovative molecular technique that enabled them to trace how processes like erosion moved carbon in deep time.

"This technique uses molecules in a really innovative, out-of-the-box way to trace fossil carbon," said Katherine Freeman, Evan Pugh University Professor of Geosciences at Penn State. "We haven't really been able to do that before."

Global temperatures increased by about 9 to 14.4 degrees Fahrenheit during the PETM, radically changing conditions on Earth. Severe storms and flooding became more common, and the warm, wet weather led to increased erosion of rocks.

As erosion wore down mountains over thousands of years, carbon was released from rocks and transported by rivers to oceans, where some was reburied in coastal sediments. Along the way, some of the carbon entered the atmosphere as greenhouse gas.

"What we found in records were signatures of carbon transport that indicated there were massive erosion regimes occurring on land," Lyons said. "Carbon was locked on land and during the PETM it was moved and reburied. We were interested in seeing how much carbon dioxide that could release."

Lyons was studying PETM core samples from Maryland, in a location that was once underwater, when she discovered traces of older carbon that must have once been stored in rocks on land. She initially believed the samples were contaminated, but she found similar evidence in sediments from other Mid-Atlantic sites and Tanzania.

Carbon in these samples did not share common isotope patterns of life from the PETM and appeared oily, as if it been heated over long periods of time in a different location.

"That told us what we were looking at in the records was not just material that was formed during the PETM," Lyons said. "It was not just carbon that had been formed and deposited at that time, but likely represented something older being transported in."

The researchers developed a mixing model to distinguish the sources of carbon. Based on the amount of older carbon in the samples, scientists were able to estimate how much carbon dioxide was released during the journey from rock to ocean sediment.

They estimated the climate feedback could have released enough carbon dioxide to explain the roughly 200,000-year duration of the PETM, something that has not been well understood.

The researchers said the findings offer a warning about modern climate change. If warming reaches certain tipping points, feedbacks can be triggered that have the potential to cause even more temperature change.

"One lesson we can learn from this research is that carbon is not stored very well on land when the climate gets wet and hot," Freeman said. "Today, we're pushing the system out of equilibrium and it's not going to snap back, even when we start reducing dioxide emissions."

Additional authors from Penn State are Timothy Bralower, Elizabeth Hajek and Lee Kump, professors of geosciences; and Ellen Polites, an undergraduate majoring in geosciences. Kump is also dean of the College of Earth and Mineral Sciences.

Researchers from the University of California Santa Cruz, the U.S. Geological Survey, the University of Delaware and the University of Louisiana at Lafayette also collaborated on this project.


Explore further

New study indicates carbon release to atmosphere ten times faster than in the past

More information: Shelby L. Lyons et al. Palaeocene–Eocene Thermal Maximum prolonged by fossil carbon oxidation, Nature Geoscience (2018). DOI: 10.1038/s41561-018-0277-3
Journal information: Nature Geoscience

Provided by Duke University
Citation: Ancient climate change triggered warming that lasted thousands of years (2019, January 21) retrieved 20 June 2019 from https://phys.org/news/2019-01-ancient-climate-triggered-thousands-years.html
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Jan 21, 2019
the climate changes. that's what chaotic systems do.

Jan 21, 2019
that could explain the long duration of the Paleocene-Eocene Thermal Maximum (PETM), which is considered the best analogue for modern climate change.

They had coal powers plants and SUV's back then?

Jan 21, 2019
that could explain the long duration of the Paleocene-Eocene Thermal Maximum (PETM), which is considered the best analogue for modern climate change.

They had coal powers plants and SUV's back then?


Meanwhile, 5 sentences later...

"Increased erosion during the PETM, approximately 56 million years ago, freed large amounts of fossil carbon stored in rocks and released enough carbon dioxide, a greenhouse gas, into the atmosphere to impact temperatures long term, researchers said.

Scientists found evidence for the massive carbon release in coastal sediment fossil cores. They analyzed the samples using an innovative molecular technique that enabled them to trace how processes like erosion moved carbon in deep time."

Jan 21, 2019
I think the truth is pretty obvious from the title of the article; "Ancient climate change triggered warming that lasted thousands of years". Between SUV's and coal, humans have basically F'ed themselves to the 'A for a couple of thousand years already. Pretty much all climate change currently is on the worst case trajectory so with Earth at +8C over average, this is going to be a painful time for a man.


Jan 21, 2019
"Global temperatures increased by about 9 to 14.4 degrees Fahrenheit during the PETM, radically changing conditions on Earth. Severe storms and flooding became more common, and the warm, wet weather led to increased erosion of rocks.

As erosion wore down mountains over thousands of years, carbon was released from rocks and transported by rivers to oceans, where some was reburied in coastal sediments. Along the way, some of the carbon entered the atmosphere as greenhouse gas."

It looks to me like the warming happened first, then CO2 was released due to increased erosion. Cart before the horse?

I don't know, but there are several articles on this site that suggest our knowledge of the PETM period is limited at best. Yet the same articles suggest this ancient period is our best analogy for modern global warming. It doesn't look like the science is settled to me.


Jan 21, 2019
@ChucktheCanuck Fuck you, denialist scum.

Jan 21, 2019
So, we don't know the origin of the first pulse that caused the PETM, but we know the reason it went on so long.

Considering we haven't seen the cause of the first pulse of AGCC other than in our own foolishness, why does this matter? What's being said here is that, no matter the cause of the first pulse, it ignites a second, far longer and more intense pulse. We have provided the first pulse, and the data is in almanacs. Which are written by economists, not scientists.

Next?

Jan 21, 2019
It's interesting reading over the theories of that initial cause. Many include a sudden injection of carbon into the atmosphere, either directly or incidentally such as a carbon-rich asteroid impact or volcanism releasing the gas or triggering secondary releases, which then had knock-on effects causing more to be released elsewhere in the system. There are no clear winning theories, all fit in some ways and not in others. As was already stated from the outset, PETM isn't a direct analogy to what we're currently experiencing, but being an analogy it's the closest thing in the geologic record we can look to. It's fascinating and, well, terrifying. This century is going to be a wild ride. A wild, terrible ride.

Jan 21, 2019
ChucktheCanuck

Ah, the standard denier mantra "CO2 follows warming"
CO2, a known powerful greenhouse gas, does not give a shit what puts it in the atmosphere. It will always exert the greenhouse effect, regardless.
It can act as a feedback adding to warming, as it does when ice ages end.
Or it can be a climate Forcing, that initiates the warming, like when humans put 38 Billion tons a year into the atmosphere. This is not hard to understand, though it seem to be for deniers, who constantly repeat the mantra. But then, they are not interested in understanding.
Shakum et al study found that when the last ice age (glacial period) ended, over an 11,000 year time frame, 93% of the warming happened After the CO2 increase.
The initial warming was triggered by orbital forcing, Milankovitch cycles.

Jan 21, 2019
Denier liars ignore positive feedbacks. They've been doing this for decades. It's simply a matter of arithmetic; they were picking their noses and eating it while arithmetic was taught to the other, non-stupid 8-year-olds.

Jan 21, 2019
cantdrive85

Can't think? Do you think "They had coal powers plants and SUV's back then?"
is actually an intelligent comment? It is not. It is idiotic nonsense worthy of a 3rd grader.


Jan 21, 2019
ChucktheCanuck

Nobody is claiming the science is settled concerning the PETM.
That humans are now causing global warming is most certainly settled science.
Did you know, that humans are increasing atmospheric CO2 100 times faster than the very fastest that nature did in the last 450,000 years, and almost certainly in 800,000 years or more? Ice core data shows CO2 levels and changes for that long ago.
We have increased CO2 by 120ppm in 138 years, The fastest that nature did that in the last 450,000 years took 20,000 years.
We have increased CO2 by 80ppm just since 1960 -58 years. One of the 6 major CO2 increases in the last 450,000 years took 80,000 years to do that.

That CO2 traps heat in the lower atmosphere, and how it does it, have been known since 1859. How much warming for a given CO2 increase was first quantified in 1896.


Jan 21, 2019
This comment has been removed by a moderator.

Jan 22, 2019
"Settled science" and arithmetic are for science kiddies who've been educated to believe that numbers cannot lie and that science is the objective arbiter sin qua non of reality. They are not aware that certainty in science died in 1904. They will tell you fervently and with religious passion that 1+1=2 everywhere and at times throughout the Universe, yet that statement of equality is not even true at all times and everywhere on Earth.... go figure!


Jan 22, 2019
It's interesting to note that the PETM witnessed a huge explosion of mammals. That warm period gave creatures like us a big boost. Presumably, a warming now will result, not merely in the extinction of species that don't evolve quickly enough, but in the development of new species adapted to the new environment, about which we cannot even yet conceive. Humanity itself may evolve into something new. The universe is a dynamic place. Get used to it.

Jan 22, 2019
sounds like an impeachable offense to me, quick call algore


"Settled science" and arithmetic are for science kiddie


HOT


Childish, and irresponsible.

The universe is a dynamic place. Get used to it.


You repeat the very first comment - it was ineffective, your players died. The discussion is about a preventive change, and the consequences if we do not prevent it.

One of those you do bring up, the diversity of existing clades and the ecologies will change irreversibly over millions of years. (5 million in the latest estimate.) Considering that mammal species becomes on average 1 Myrs - our ancestral Erectus became 2 Myrs-- and we are already closer to 0.5 Myrs (0.3 more precisely), humans will never see your putative "good effects"..

And the latest paper I saw on diversity after mass extinctions was that the result was precisely chaotic for any measures of "good/bad", Get used to it.

Jan 22, 2019
"It doesn't look like the science is settled to me."

- Chuck the Dumb Fuck Canuck

Too dumb to even consider conversing with. You are now ignored, Dumb Fuck.

Jan 22, 2019
As is this mental midget - petersonwalter

Jan 23, 2019
When I first glanced at the headline it seemed to read: "Ancient climate change triggered warning that lasted thousands of years." Hehe.

Jan 23, 2019
the climate changes. that's what chaotic systems do.

yes, and in this case one aspect of those changes can be triggered by our activity.

Jan 28, 2019
Part of the modelling problem may be assuming that the earth's crust and biosphere is a closed system with a constant amount of carbon.

I wonder if the cooling of the earth core & mantle can result in chemical equilibrium shifts that eject significant amounts of CO2 and other carbon compounds to the surface. Especially carbon and oxygen dissolved in iron. Those changes might also be intertwined with shifts in the earth's magnetic field. There might be stairsteps composed of natural tipping points there as well. Followed by absorption into the biosphere.

Jan 28, 2019
Yes humans (especially overpopulated billions of humans) are a factor in modern climate change. But I see nothing that says natural change stops because humans arose. Nor am I convinced that the biosphere is a closed system unaffected by by internal processes of the earth's core and mantle.

Similarly long term statistics about environmental conditions can lie to short term oriented humans - because truly chaotic systems don't necessarily spread changes or rare events around evenly. There is no guarantee of 25K years separation for events that have averaged . 25K cycles in the "recent" past. Scale your thinking to the fact that the Earth is about 4.5 billion years

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