Study of ancient climate suggests future warming could accelerate

clouds
Credit: CC0 Public Domain

The rate at which the planet warms in response to the ongoing buildup of heat-trapping carbon dioxide gas could increase in the future, according to new simulations of a comparable warm period more than 50 million years ago.

Researchers at the University of Michigan and the University of Arizona used a state-of-the-art model to successfully simulate—for the first time—the extreme warming of the Early Eocene Period, which is considered an analog for Earth's .

They found that the rate of warming increased dramatically as carbon dioxide levels rose, a finding with far-reaching implications for Earth's future climate, the researchers report in a paper scheduled for publication Sept. 18 in the journal Science Advances.

Another way of stating this result is that the climate of the Early Eocene became increasingly sensitive to additional carbon dioxide as the planet warmed.

"We were surprised that the climate increased as much as it did with increasing carbon dioxide levels," said first author Jiang Zhu, a postdoctoral researcher at the U-M Department of Earth and Environmental Sciences.

"It is a scary finding because it indicates that the temperature response to an increase in carbon dioxide in the future might be larger than the response to the same increase in CO2 now. This is not good news for us."

The researchers determined that the large increase in climate sensitivity they observed—which had not been seen in previous attempts to simulate the Early Eocene using similar amounts of carbon dioxide—is likely due to an improved representation of cloud processes in the climate model they used, the Community Earth System Model version 1.2, or CESM1.2.

Global warming is expected to change the distribution and types of clouds in the Earth's atmosphere, and clouds can have both warming and cooling effects on the climate. In their simulations of the Early Eocene, Zhu and his colleagues found a reduction in cloud coverage and opacity that amplified CO2-induced warming.

The same cloud processes responsible for increased climate sensitivity in the Eocene simulations are active today, according to the researchers.

"Our findings highlight the role of small-scale cloud processes in determining large-scale climate changes and suggest a potential increase in climate sensitivity with future warming," said U-M paleoclimate researcher Christopher Poulsen, a co-author of the Science Advances paper.

"The sensitivity we're inferring for the Eocene is indeed very high, though it's unlikely that climate sensitivity will reach Eocene levels in our lifetimes," said Jessica Tierney of the University of Arizona, the paper's third author.

The Early Eocene (roughly 48 million to 56 million years ago) was the warmest period of the past 66 million years. It began with the Paleocene-Eocene Thermal Maximum, which is known as the PETM, the most severe of several short, intensely warm events.

The Early Eocene was a time of elevated atmospheric carbon dioxide concentrations and at least 14 degrees Celsius (25 degrees Fahrenheit) warmer, on average, than today. Also, the difference between temperatures at the equator and the poles was much smaller.

Geological evidence suggests that atmospheric carbon dioxide levels reached 1,000 parts per million in the Early Eocene, more than twice the present-day level of 412 ppm. If nothing is done to limit carbon emissions from the burning of fossil fuels, CO2 levels could once again reach 1,000 ppm by the year 2100, according to climate scientists.

Until now, climate models have been unable to simulate the extreme surface warmth of the Early Eocene—including the sudden and dramatic temperature spikes of the PETM—by relying solely on atmospheric CO2 levels. Unsubstantiated changes to the models were required to make the numbers work, said Poulsen, a professor in the U-M Department of Earth and Environmental Sciences and associate dean for natural sciences.

"For decades, the models have underestimated these temperatures, and the community has long assumed that the problem was with the geological data, or that there was a warming mechanism that hadn't been recognized," he said.

But the CESM1.2 model was able to simulate both the warm conditions and the low equator-to-pole temperature gradient seen in the geological records.

"For the first time, a climate model matches the geological evidence out of the box—that is, without deliberate tweaks made to the model. It's a breakthrough for our understanding of past warm climates," Tierney said.

CESM1.2 was one of the climate models used in the authoritative Fifth Assessment Report from the Intergovernmental Panel on Climate Change, finalized in 2014. The 's ability to satisfactorily simulate Early Eocene warming provides strong support for CESM1.2's prediction of future warming, which is expressed through a key climate parameter called equilibrium climate sensitivity.

The term equilibrium climate sensitivity refers to the long-term change in global temperature that would result from a sustained doubling—lasting hundreds to thousands of years—of carbon dioxide levels above the pre-industrial baseline of 285 ppm. The consensus among climate scientists is that the ECS is likely to be between 1.5 C and 4.5 C (2.7 F-8.1 F).

The equilibrium climate sensitivity in CESM1.2 is near the upper end of that consensus range at 4.2 C (7.7 F). The U-M-led study's Early Eocene simulations exhibited increasing equilibrium with , suggesting an Eocene sensitivity of more than 6.6 C (11.9 F), much greater than the present-day value.


Explore further

More sensitive climates are more variable climates, research shows

More information: "Simulation of Eocene extreme warmth and high climate sensitivity through cloud feedbacks" Science Advances (2019). advances.sciencemag.org/content/5/9/eaax1874
Journal information: Science Advances

Citation: Study of ancient climate suggests future warming could accelerate (2019, September 18) retrieved 23 October 2019 from https://phys.org/news/2019-09-ancient-climate-future.html
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Sep 18, 2019
Is it Holocene Thermal Maximum yet? Lasting 4000 years? No?

Call me.

Sep 18, 2019
Is it Holocene Thermal Maximum yet? Lasting 4000 years? No?

You always bring that up when an article so much as mentions climate but I and perhaps others have explained to you that the Holocene Optimum was not a global event and global temperatures during this time were essentially the same as they are now. Europe saw a heat spike, other parts of the world saw cooling.
Call me.

What's your number?

Sep 18, 2019
Earth's elliptical orbit and the axial wobble of our planet create constantly changing climate.

Sep 18, 2019
Deniers will be screaming "HOAX!" as they die of heatstroke.

Sep 18, 2019
No doubt about it in just a generation or two, planet Earth could be in the middle of a very rapid die off of every living thing. The very rapid increase in Anthropogenic Global Warming will have pushed the planet right into an apocalypse. I really don't see much of a future left for the deniers other than listening to them complain about all of their flake rightwing ideals being stepped on by the Democrats. Oh poor you... deniers boohuhuhoo.

The latest predictions have a 7C rise in them by 2100 but we are trending towards 8C due to inaction and a lack of leadership. That means an accelerated sea-level change, rapid and massive heat waves of increasing lengths, more violent storms and a severe impact on food supplies and trading routes. We'll begin to see extinctions etc. Lastly, we'll see financial collapse and chaos descends globally.

On your grave will be written "Oh boy, what fun it must have been to be a Trump supporter."

Sep 18, 2019
@howhot, and that's assuming the growing water crises near the Equator don't wind up triggering water wars, probably including nuclear weapons since there are several countries likely to be affected by these water shortages (and more important, the crop shortages they create) that have nukes. Think they won't use them? I think they will. The other choice is food riots and we aren't talking about governments that respect individual people. They are vermin to the rich and powerful, but dangerous vermin. Better to have a nuclear war than get strung up from a lamppost, is the way these governments think.

Sep 18, 2019
We have GOT to stop burning coal! Sorry for shouting, but this doesn't appear to be getting across to people. This is the single most important issue in the world today.

Sep 18, 2019
age, "Earth's elliptical orbit and the axial wobble of our planet create constantly changing climate."

unless you live in a mystical faarie-land with all the other deniers?

here on this planet?
trapped in self-inflicted reality

the enormous burden inflicted on the biosphere, of supporting the hordes of destructive Humanity, is difficult enough to sustain

yep, climate change is a normal, if unpredictable, chain of events
the additional problems of Human civilization making a bad situation worse
at high speed
it is the destructive intervention of anthropophagus instincts that we refuse to control

if we kill this world?
i'm calling it "The Matricide"
there ain't no where to run & hide

too many people, out of deliberate spite
refuse to make any effort to save this world
as long as we can deprive others of existence

you read the comments of the senile denial-cults?
they blatantly want the hope of a better future to die when their worthless existence ends

Sep 18, 2019
Who the hell downvotes the single most important action humans must take today to prevent mass death of humans tomorrow?

That's what people who think others are going to do the dying and don't care because their language or their religion or their skin color is "bad" do.

Simple as this: stop burning coal. Or maybe do the dying yourselves.

Sep 18, 2019
What's your position, anyway, "burn more coal?"

Sep 18, 2019
DSm as long as he is getting paid by the coal lobby?

the answer is yes, that's exactly what he wants

& if he's trolling for free?
all the other denierbots will mock & jeer at him for not getting his 24 pieces of silver

Sep 18, 2019
dangerous lunatics propose sending earth into another ice age

https://www.natur...-07533-4

Sep 18, 2019
which had not been seen in previous attempts to simulate the Early Eocene using similar amounts of carbon dioxide—is likely due to an improved representation of cloud processes in the climate model they used,

so they know all about what eocene clouds wer like , ie we found a way to tweak the model to get the result we wanted

Sep 18, 2019
@snooze, you didn't say "burn more coal." Stop dodging and step up and bat. Or admit your own doubts.

Sep 19, 2019
It's not only time to stop burning coal, it's also time to get serious about geoengineering. Otherwise we won't have a hope in hell.

Sep 19, 2019
Predicting the future is hard but we do it all the time with weather models that extend a week or two in advance. But just a couple of years ago those long-range predictions weren't that good. So just a couple of years ago we all thought we could stop AGW at 2C in 2100 with 8C a possible worst case. Models improved, time went on and the outlook looked tended toward 4C but 2.5C if we acted then. There was just not enough action and then there was outright hostility towards law restricting the creation of CO2, with a repeal of efforts to attack the issue. It follows that 7C Average global temperature rise is now the projected new normal with 8-10C as possible.

If that is not madness ... what is deniers?

Sep 19, 2019
The Bering Sea, home of Halibut and King Crab, and road for Salmon to reach spawning streams, has warmed up.
Warmed up twelve degrees on the bottom, allowing Pacific Cod, previously stopped by cold water, to increase by a factor of twenty. Twenty times more cod, eating the King Crab as well as starving the Halibut of ocean bed nourishment.
The Salmon are dying in the warm streams due to no oxygen at the higher temperatures. Not a big deal now but in five years when all the salmon are returning to get caught trying to spawn again there will not be any due to no eggs laid this year.

This is going to hurt. Also causing pain is the continuing rise in temperature, especially in the tropics where climate refugees are already causing major exodus and famine.

The shooting wars have begun over resources as well.
Denial is the only thing the ignorant have left to hold on to. It is certainly too late to stop and preparation takes intelligence deniers do not have.

Denial, pathetic and sad.

Sep 19, 2019
It was up to 15 degrees C warmer in past history with plenty of life everywhere.
And more alarmist crap science, claiming CO2 rise causes heat rise. When the reality is; CO2 rise follows the heat rise. Fools.

Sep 20, 2019
wow oldcoot,
i surely wish i had your time machine
& could escape back to a previous century,
with a smaller population, causing less devastation to this world's biosphere

either that or your are pounding down some primo peyote?
"don't bogart that joint, my friend..."

Sep 21, 2019
So, there *are* runaway effects in greenhouse gas warming. Scary!

Earth's elliptical orbit and the axial wobble of our planet create constantly changing climate.


Yes, like those that helped the transition between the Pliocene and current Pleistocene. And your point was? If it was that these changes are dramatic and scary, especially when we humans force them at 1000 times the wobble response rates, point well taken: this is so much worse!

Sep 21, 2019
I once saw a cartoon, a room full of lab-coated people hanging their heads and looking despondent, with one in the foreground telling someone else,"The final test results are in. EVERYTHING causes cancer."
Everything causes global warming. Right?

Sep 21, 2019
It's not only time to stop burning coal, it's also time to get serious about geoengineering. Otherwise we won't have a hope in hell.

If you don't get emissions down to zero, geoengineering won't work. As an example, in the case of the most commonly described geoengineering, injecting aerosols into the atmosphere, if something causes that aerosol injection to stop (war, accident, etc.), the warming increases rapidly and exceeds the current warming due to the additional GHGs that have been put in the atmosphere. This leads to additional disasters that may prevent a return to geoengineering. So if you plan on doing geoengineering, you need to stop emitting GHGs. And if you stop emitting GHGs, then you really don't need geoengineering.

Sep 21, 2019

I once saw a cartoon, a room full of lab-coated people hanging their heads and looking despondent, with one in the foreground telling someone else,"The final test results are in. EVERYTHING causes cancer."
Everything causes global warming. Right?

Well, the current "truth" is that man-made CO2 is responsible for global warming. But, as reality increasingly poke holes in that fib, they will continue, until they blame and discard, EVERYTHING. Finally, left with a planet of ignorant people, hanging their heads and looking despondent, one in the foreground will tell another; "The final test results are in. Global warming caused EVERYTHING".

Sep 21, 2019
@antigoracle.
Well, the current "truth" is that man-made CO2 is responsible for global warming. But, as reality increasingly poke holes in that fib, they will continue, until they blame and discard, EVERYTHING. Finally, left with a planet of ignorant people, hanging their heads and looking despondent, one in the foreground will tell another; "The final test results are in. Global warming caused EVERYTHING".
I would have liked to have been there to witness the group of doctors and nurses gathered around the consulting room hanging their heads and looking despondent while one of them in the foreground tried to tell your parents that there was no cure for 'weapons-grade-stupidity'; but that they shouldn't blame themselves because there is only so much that nurture can do in the face of nature's sometimes nasty surprises. I wonder if your parents know what you have been doing for your 'thirty pieces of silver'. Probably better they didn't know what you are/do, @antigoracle. Sad.

Sep 21, 2019
Well @RC, I hope you can at least find some consolation in being there when your parents admitted, your stupidity, incurable. Now there is a "fix" for your crazy, so be a good idiot, and go take your meds.

Sep 21, 2019
@antigoracle.
I would have liked to have been there to witness the group of doctors and nurses gathered around the consulting room hanging their heads and looking despondent while one of them in the foreground tried to tell your parents that there was no cure for 'weapons-grade-stupidity'; but that they shouldn't blame themselves because there is only so much that nurture can do in the face of nature's sometimes nasty surprises. I wonder if your parents know what you have been doing for your 'thirty pieces of silver'. Probably better they didn't know what you are/do, @antigoracle.
Well @RC, I hope you can at least find some consolation in being there when your parents admitted, your stupidity, incurable. Now there is a "fix" for your crazy, so be a good idiot, and go take your meds.
Your 'comebacks' are getting more feeble and lame by the day now, mate. A sure sign that your 'weaponised stupidity' is not achieving what your 'handlers' paid for. Not good for them or you. :)

Sep 21, 2019
Nah @RC, that there is just crazy talk. Now, if you could just be a good idiot and go take your insanity pills, even stupid you will see that.

Sep 21, 2019
@antigoracle.
Nah @RC, that there is just crazy talk. Now, if you could just be a good idiot and go take your insanity pills, even stupid you will see that.
The pharmacy was all out of "insanity pills', mate. It seems some crazy has cornered the market of same. Gave his name as "@antigoracle": care-of a troll-factory address somewhere in Russia, and marked: for use in 'weaponised stupids' injection-room. Are you their Internet 'insanity pills' buyer as well as their Internet 'weaponised stupid' representative, mate? Sad.

Sep 22, 2019
So @RC, thanks for the confirmation, I knew that was crazy talkin'. So sorry about the pills, mate. I told some people I wanted to try and experience your mind, well the crazy bit. Since there is no way on god's green earth that I'm going subject myself to severe head trauma, just to negotiate the minefield that is your kind of stupid. Anyway, they told some people who told some people and then they were all curious about your condition. Hence, the pills situation. No worries though, the pharmacy will have you covered tomorrow. Happy.

Sep 22, 2019
@antigoracle.
So @RC, thanks for the confirmation, I knew that was crazy talkin'. So sorry about the pills, mate. I told some people I wanted to try and experience your mind, well the crazy bit. Since there is no way on god's green earth that I'm going subject myself to severe head trauma, just to negotiate the minefield that is your kind of stupid. Anyway, they told some people who told some people and then they were all curious about your condition. Hence, the pills situation. No worries though, the pharmacy will have you covered tomorrow. Happy.
You, the 'weaponised stupid' and/or 'denialism-programmed bot' named @antigoracle "told some people", you say? Ain't that 'nice', you 'telling some people' about the "insanity pills" being used in your Russian.GOP/Fossil-funded Troll-Factory 'injection room' where you and your fellow 'weaponised stupids' go 'insane' together. What a scene: drivelling 'run-of-the-mill stupids' being turned into drivelling 'hyper-stupids'. :)

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