Global warming: Our best guess is likely wrong
No one knows exactly how much Earth’s climate will warm due to carbon emissions, but a new study this week suggests scientists’ best predictions about global warming might be incorrect. The study, which appears in Nature Geoscience, found that climate models explain only about half of the heating that occurred during a well-documented period of rapid global warming in Earth’s ancient past. The study, which was published online today, contains an analysis of published records from a period of rapid climatic warming about 55 million years ago known as the Palaeocene-Eocene thermal maximum, or PETM.
“In a nutshell, theoretical models cannot explain what we observe in the geological record,” said oceanographer Gerald Dickens, a co-author of the study and professor of Earth science at Rice University. “There appears to be something fundamentally wrong with the way temperature and carbon are linked in climate models.”
During the PETM, for reasons that are still unknown, the amount of carbon in Earth’s atmosphere rose rapidly. For this reason, the PETM, which has been identified in hundreds of sediment core samples worldwide, is probably the best ancient climate analogue for present-day Earth.
In addition to rapidly rising levels of atmospheric carbon, global surface temperatures rose dramatically during the PETM. Average temperatures worldwide rose by about 7 degrees Celsius — about 13 degrees Fahrenheit — in the relatively short geological span of about 10,000 years.
Many of the findings come from studies of core samples drilled from the deep seafloor over the past two decades. When oceanographers study these samples, they can see changes in the carbon cycle during the PETM.
“You go along a core and everything’s the same, the same, the same, and then suddenly you pass this time line and the carbon chemistry is completely different,” Dickens said. “This has been documented time and again at sites all over the world.”
Based on findings related to oceanic acidity levels during the PETM and on calculations about the cycling of carbon among the oceans, air, plants and soil, Dickens and co-authors Richard Zeebe of the University of Hawaii and James Zachos of the University of California-Santa Cruz determined that the level of carbon dioxide in the atmosphere increased by about 70 percent during the PETM.
That’s significant because it does not represent a doubling of atmospheric carbon dioxide. Since the start of the industrial revolution, carbon dioxide levels are believed to have risen by about one-third, largely due to the burning of fossil fuels. If present rates of fossil-fuel consumption continue, the doubling of carbon dioxide from fossil fuels will occur sometime within the next century or two.
Doubling of atmospheric carbon dioxide is an oft-talked-about threshold, and today’s climate models include accepted values for the climate’s sensitivity to doubling. Using these accepted values and the PETM carbon data, the researchers found that the models could only explain about half of the warming that Earth experienced 55 million years ago.
The conclusion, Dickens said, is that something other than carbon dioxide caused much of the heating during the PETM. “Some feedback loop or other processes that aren’t accounted for in these models — the same ones used by the IPCC for current best estimates of 21st Century warming — caused a substantial portion of the warming that occurred during the PETM.”
Source: Rice University
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
@Stefan
Well said!
I imagine the geologic positions of the continents played a part in this overall time period.
At the south pole, the deep ocean was able to circulate all the way to the pole (or very near to it). This allowed warm and cold water to be exchanged at a maximum rate and kept the south pole in a maritime climate.
At the north pole, the smaller Arctic ocean seems to be nearly completely cut-off in the reconstructions. The north Atlantic was just starting to open at this point.
It is possible that this Atlantic opening happened in a way that allowed the oceans to completely enter and exit the Arctic efficiently (and/or perhaps the Pacific side also opened at the same time) and this took the Earth from having a warm south pole and a cold north pole to a world which had both a warm south pole and a warm north pole. Any other time this has occurred in geologic history, the earth has been quite warm.
Earth 50 million years ago – a little after this event.
http://jan.ucc.nau.edu/~rcb7/050_Eocene_sm.jpg
(Likely redundant, but I can’t help myself…)
“There appears to be something fundamentally wrong with the way temperature and carbon are linked in climate models.”
DUH!
RE: Leif Svalgaard (19:14:39) :
If I didn’t know any better, the conclusion one might draw is that if climate models only predict half the actual warming due to CO2, then the effect of AGW would be twice what is predicted…
——————————————-
That is how the alarmist end of the media are playing this. Their argument is along the following lines:
“Our computation of carbon effect on climate accounts for only half of that rapid warming, so there is some terrifying effect that we do not understand yet that means that our current contribution of dirty, polluting, poisonous greenhouse gas may have twice as bad an effect as our models predicted.”
Funny how the alarmists can only ever accept that their models are wrong when they think that the outcome could be worse. Never the other way round. They only accept error when they think the models could be underestimating the carbon effect.
IF there was such a dramatic carbon effect, then why have we not seen much greater increases over the last 30 years? We are currently closer to the average over that time than we are to the cataclysmic predictions of the alarmists.
I mean we have only had 0.6 degrees of warming over a century and that is if you take the “anomolies” and piss poor recording of temperatures. It has likely been rather less than that in reality. Probably closer to 0.3 degrees. That level of climate change is actually, remarkably still. In historical terms, that is as close to stasis as you are going to get, so I really do not see a lot to be getting all steamed about.
The massive changes in temps back in the PETM are way outside of what we are getting all steamed up about now.
Could it not be that actually, most of the massive increase in temps back then had nothing to do with carbon? What was the sun doing? how about volcanic activity under the oceans? Was there any super massive meteorites hitting the earth then? What about the orbit of the earth, was that any nearer the sun back then? What about cloud cover? what about conditions which may have existed naturally back then that no longer exist and we have no clue about?
Grumbler (02:29:00) :
“gtrip (23:51:05) :
What dreadful hot weather we have! It keeps me in a continual state of inelegance.
Jane Austen (1775-1817) English novelist, author of “Sense and Sensibility”
What a nice way to say ’sweating like a pig!”
Recommended reading:
“Jane Austen’s Irony as Received in Film Adaptations” (Sorboe, M.N., Doctoral Thesis, Institute for Litterature, Oslo University 2008)
Trial Lecture: “Your haven in a world programmed to misunderstand obsession with things Austen’: Austen, film, and reception on the World Wide Web.” (Oslo University, 9 January 2009).
I believe Jane Austen would see and quite elegantly express the irony of the present day obsession with man-made climate politics.
This should come as no surprise to readers here. Afterall the difference between a water vapour positive feedback to temperature (in the models) and a negetive feedback (most likely in reality) is a massive difference in outcome.
In the models doubling of CO2 (worth 1 to 2 C of warming) gets positive feedbacked to anywhere between 4 and 8 C .
In the real world the feedback works the other way and we will mostly likely see around 1C of warming.
No-one can say for sure what caused the 7C of warming 55m years ago. One thing is certain it wasn’t caused by CO2. CO2 would have lagged the temperature rise , but still caused 1-2 C of warming due to its positive feedback.
So where does the initial temp rise come from?
Solar output variation has been suggested, but where is the evidence for this?
Ocean currents warming the arctic. There was no Ice at the poles 55m years ago so getting 5C of warming from this seems unlikely.
This event lasted 20,000 years so what is left. Some kind of albedo related event, making the Earth’s surface darker? To get the required temp increase would mean dropping the albedo from 0.3 to 0.26 , that’s a lot of stagnant algal bloom in the sea?
Frank Lansner (04:10:27) : I have a far out hypothesis. We have been observing stars for only a few hundred years. Maybe thousands if you include naked eye observations. We certainly don’t have data on stars going back millions of years and that is the point. What if the Sun is an irregular variable star? I suspect the increase in brightness wouldn’t have to be a lot in order to cause the inferred warming. I hate to go here, but what proxy could we look for? Increased melanin, assuming we can find any? Anything?
John Edmondson (06:02:35) :
This event lasted 20,000 years so what is left. Some kind of albedo related event, making the Earth’s surface darker? To get the required temp increase would mean dropping the albedo from 0.3 to 0.26 , that’s a lot of stagnant algal bloom in the sea?
So ,how about this?
http://www.mcclatchydc.com/environment/story/71842.html
” Hunters from Wainwright first started noticing the stuff sometime probably early last week. It’s thick and dark and “gooey” and is drifting for miles in the cold Arctic waters, according to Gordon Brower with the North Slope Borough’s Planning and Community Services Department.”
Clearly from the above article and subsequent comment there is not one single person on the planet who has any idea why our climate changes in this way or that, basically Mother Nature doesnt do sums and behaves exactly as she wants to at any given time and trying to make sense or logic of it is an absolute waste of time and energy. We may reduce Co2 and whilst in the process Mum might just decide that what we really need to give us some excitement is to allow Yellowstone to erupt, turn the sky black and push us into another ice age, then we all get to freeze to death and maybe after reading all of the guff above that might not be such a bad idea. There appears to be zillions of idiots who would prefer to argue the toss about a subject they clearly do not understand or ever have a chance of understanding that just getting on with their lives in the sure knowledge that one way or the other at some point in time you will be no more than dust. With a population of 6.77 billion and rising at some point there will just be insufficient habitat for anyone to exist. Common sense says that Co2 can never be the answer as to why our climate changes, it just does, it is chaotic, there is no formula and no reason and certainly throughout all of the magnificent catastrophies that have occurred with or without us there is no logic and no reason that can be attached. Earth is a lump of rock spinning through space, we are no more than a quirk of nature, get used to it and stop trying to find reason where non exists, enjoy whilst you are here because you really dont know – and never will know – just how long you have. We will all go to hell in a handbasket because a population of 10 billion is clearly unsustainable whichever way our climate goes hot or cold, out of preference a few degrees higher is more agreeable, 2 degrees cooler and you get no food whatsoever!
David Wells
According to a BBC Horizon prog some years ago now, I understood that one theory of mass extinction c500MYA, was volcanic Basalt lava eruptions in what is now Siberia that lasted for million(s) of years, when the Earth was in Pangea, raising Earth’s temp by 5°C. This then allowed (theoretically) methane clathrates (another scary story) to melt in the oceans & seas raising the Earth’s temp a further 5°C, which theoretically killed off 95% of the life on Earth! Question, now why could it not be anything to do with CO2 raising temp, but simply the massive heat exchange into the atmosphere from billions of tons (or tonnes if you prefer) of molton rock spewing out causing the CO2 to be released from the seas & oceans, as well as that from the eruptions themselves & from subsequent mass eruptions? The heat had to go somewhere & do something & the outgassing must have been significant! Or am I too simple & dumb?
David Wells (06:40:56) :
“We will all go to hell in a handbasket because a population of 10 billion is clearly unsustainable”
How did you arrive at this conclusion?
Why not give the Paleocene Eocene Thermal Reconstruction data to the people at GISS. Chances are they can adjust it to be in line with the current models.
rbateman (23:02:07):
It’s not the modern civilization that I wonder about. I know what they are doing with underground dwellings (escaping heat & cold, making wine and cheeses, etc.)… It’s the prehistoric hunter/gatherers. You can’t take a cave with you to follow the herds.
There were not humans on Earth 55 million years ago. The first hominids lived in Africa ~ 8 million years ago, during the Pliocene. Anthropoids appeared during the Eocene, when the fluctuation of temperature was 13 °C. The first hunters’ communities appeared around 500 thousand years ago. Prior to this date, meat-eaters hominids were scavengers.
I don’t see what the fuss is about.
The man-made global warming hypothesis is dependent on current warming being caused by CO2. The fact that previous warming is half an order of magntude higher for a period with a 70% CO2 rise is irrelevant. It is obvious that either the temperature measurement is wrong or there was another force at work. There is no evidence beyond “we can’t find anything else” that CO2 was the cause of the PETM warming. Whether CO2 aided, hindered, or sat idle while that other cause warmed the Earth is unknowable from this data.
In short, this isn’t evidence for either side of the debate, and anyone who brings it as evidence for or against the CO2-Temperature link is misconstruing evidence and deserves to have their degree revoked.
Now, one thing that I can say is that it does show that large-scale warming doesn’t necessarily cause mass extinctions. That’s all it shows.
Frank Lansner (04:10:27) :
solving the question how global change, including warming, could occur without a change in the isotopic composition of the exogenic carbon pool .
I’m a bit lost about the relevance of this. The topic is about that the models only predict half of the change that was observed during PETM. My observation was that if so, the models might also underpredict the current rise, and if so, that even larger rises may be in store for us, either from unknown causes or because the models are wrong and the real changes are twice the predicted ones. The scenario need not be linear, the unknown causes or the error in the models may not have hit yet. I have not verified [don’t know if I even can] the statement that ‘the models only predicts half the rise’, so perhaps all this is just fluff. My point is that I don’t see how this paper can be seen as a debunking of AGW. Rather the opposite, it seems to me.
Robert Kral (20:04:24) :
Come on, Leif, didn’t you read the whole thing?
The conclusion, Dickens said, is that something other than carbon dioxide caused much of the heating during the PETM. “Some feedback loop or other processes that aren’t accounted for in these models — the same ones used by the IPCC for current best estimates of 21st Century warming — caused a substantial portion of the warming that occurred during the PETM.”
Some over-interpretation of much and substantial. As I read it ‘half’ was CO2, the other half is then ‘much’ and ‘substantial’. So, the authors seem to concur that IPCC is half-right, and if so AGW is a huge problem [double of what Al Gore and IPCC claim].
Much more likely the PETM just shows that large fluctuations occur naturally and that we can’t [and therefore shouldn’t try very hard to] do much about it.
By the way, all this issue of CO2 and global warming will surely be forgotten , even temperature records will get back to normality if everbody accepts to pay a bit more for the energy we use.
Leif Svalgaard (08:26:06) : I’m not getting your logic. The fact that the models only predict half the warming does not prove CO2 is the cause of any past warming. One logical conclusion is that the models don’t work. But the fact that the models don’t work in no way implies any temperature changes past or present are anthropogenic. Explain yourself.
Energy can be released as movement also, as in this morning’ s big earthquake in New Zealand, so, what if accumulated heat (energy) is released as such?
Jim (09:18:46) :
The fact that the models only predict half the warming does not prove CO2 is the cause of any past warming. One logical conclusion is that the models don’t work. But the fact that the models don’t work in no way implies any temperature changes past or present are anthropogenic.
Suppose that the models explained 99% of the warming. Then you could say that they work. If they explained 90%, you could still say that they work, but that they are missing a tiny bit. If the explain 80%, they still work, but are missing a bit more. As long as that explain a significant fraction, they still work but are missing some additional factor (maybe volcanism, methane, whatever). If they explain X%, etc. One can quibble about what X should be. Normally in science, a model that explains 50% is not too bad, one just has to identify the additional factor [which should be easier since we can now remove the 50% explained by the model and look at the residual]. If one posits from the outset that the models don’t work, or the data is wrong, then there really can be no scientific discussion. My problem with the paper is that I don’t see where they state that that the models were run with the [some of them unknown] conditions back then.
Leif Svalgaard (10:10:22) :
1. From what I have read, the models don’t do a very good job of explaining recent temperatures, so I’m not ready to say they are working. AFAIK, the models as they stand don’t prove the recent climate changes are due to man-made CO2.
2. If I knew the models were based 100% in physics with no adjustable parameters and one could input the appropriate initial conditions and replicate a past temperature dataset for some, even if small, amount of time; then I might rely on the model to tell me how the climate works. But since climate is chaotic, such a model would not allow me to predict longer term temperatures.
3. You have to assume the models are working in order to do as you describe. That assumption seems invalid.
Jim (10:25:42) :
3. You have to assume the models are working in order to do as you describe. That assumption seems invalid.
Based on what? No model is perfect. A model explains a certain amount X of the variance [or change]. To posit that the model is wrong you are saying that X is zero. That has to be justified. I’m saying that X is greater than zero, and that the model explains that part. If X is small, the model is not very useful. So it comes down to what X is. It could well be 50%, I don’t think we know. What is your estimate of X?
The Missing, forgotten and Only Factor: The Sun.
That inconvenient, “invisible” for many, oil-painted fireball on heavens’ spheres. Heh! 😉
Are there any proxies for solar irradiation indices which can be measured in a similar way for the PETM? Would be interesting to know, wouldn’t it??
Leif,
The paper did model the PETM climate – the climate sensitivity is directly extracted from the derived values of CO2 injected into the atmosphere and the temperature change from the isotopic ratios.
There is no big discrepancy between this value of climate sensitivity and the values from current models – it’s just at the upper end of the range. It’s not even obvious that there should be good agreement – the climate was several degrees warmer then than now and there was 1000 ppm of CO2 even before the injection event. Hence the climate sensitivity could have been substantially shifted from today’s values.
The perfect model of a wood fire would, presumably, be an identical wood fire. So if I lay two identical fires and light them identically, can I reasonably expect the burning of the wood to be identical 30 mins. later?
Seems to me that a perfect model of our climate wouldn’t be able to reproduce itself from identical inputs, let alone model the climate.
So if a perfect model gives us pretty possibilities but piss-poor prophecies by its very nature, how come they expect us to buy simplistic rubbish?