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
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Leif,
Read the last Paragraph! It states:
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.”
Especially the first sentence! “Something other than carbon dioxide caused much of the heating during the PETM.
So Climate Models are not getting the TOTAL picture in their runs. Which means inaccuracies galore! Something Us “Realists” have been trying to say for some time!
Bill Illis (18:20:27) :
I have charted the temp vs CO2 data over this period and there is really a poor correlation between the two. This chart also shows the important continental drift timelines which are fundamental to understanding this climate period.
http://img20.imageshack.us/img20/2464/tempvsco267m.png
[I added the new CO2 data at 1700 ppm during the short PETM 55 million years ago (there are other CO2 estimates which are lower and some people prefer to talk about the Eocene Thermal Maximum as lasting 5 or 6 million years rather than the short spike that this paper is about)].
—
Gee. I wonder why the ever-so-qualified “peer-reviewed researchers” at Rice didn’t think to do that simple little analysis> /sarcasm
2) I expect RC to be in FULL DEFCON 1 RETALLIATION/DAMAGE CONTROL tomorrow….
And who would notice?
Many major mammalian orders – including the Artiodactyla, horses, and primates – appeared as if from nowhere and spread across the globe 13,000 to 22,000 years after the initiation of the PETM.
Ruminants arrived on the scene and ate all the vegetation, releasing CO2.
Although Wikipedia also says major ocean currents reversed during this time and ocean currents wouldn’t be linked to a biological evolutionary event.*
Which makes me think the CO2 rise and temperature rise are a coincidence.
* I can think of one reason. Previously separate land masses joined like the way S America got joined to N America a few million years ago changing ocean circulation. The ruminants which had evolved on one land mass migrated to the new land mass.
Smokey (19:26:18) :
Here’s the money quote:
“The researchers found that the models could only explain about half of the warming that Earth experienced 55 million years ago.”
Like you, my take on this is that modern AOGCMs are NOT skillful both for today’s climate AND for the climate the earth experienced 55 million years ago! However, this is still surprising given that this is a hindcast and climate models can usually perform fairly well when you know the answer beforehand…
Speaking of which, thanks mostmuch, Mr. Illis, for posting that chart; very interesting.
And that was what crossed my mind, Lief Svalgaard. Earth during the Eocene WAS different geologically and climatologically than now (it was a warmer world in general, Gondwana hadn’t completely disintegrated so the oceanic currents were different, etc.), but even so it wasn’t different enough that there wouldn’t be similarities between how the climate responded then and how the climate will respond now. Which, if this paper’s conclusion holds up, is somewhat frightening. Comforting in an odd way as well, though, because although the Eocene thermal maximum was nasty for a lot of life, (and Yes, I know, after it there was a lot of diversification among mammalian life. That’ll happen after an extinction; the survivors radiate out to fill the vacated niches) it certainly doesn’t rank up there as on of the Big Five mass extinctions–and we’re only about halfway to a 70% increase in CO2, as well, although feedback mechanisms might drag the concentration up to ~500 ppm without any further help from us, in any case.
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…
Come on, Leif, didn’t you read the whole thing? The salient point is below.
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.”
George,
A 70% increase in CO2 gives 77% of the temperature rise associated with CO2 concentration doubling, not 38%. This gives the 3.5 degC rise calculated in the paper assuming an upper value of climate sensitivity, DT, of 4.5 degC per doubling of CO2, leaving 1.5 to 5.5 degC unaccounted for.
This looks as if it might be quite a large error, but I’m not as sure as the authors of this paper that there is a serious discrepancy here. The larger the climate sensitivity, DT, the greater the uncertainty in its value. This is because there needs to be a lot of positive feedback to cause such a high value of sensitivity. If the reference sensitivity without feedback is DT0, as the feedback factor, f, approaches 1 the sensitivity given by DT = DT0/(1-f) becomes large and highly responsive to small changes in f (see Roe and Baker, Science 318, p629 (2007)).
Using the accepted value of DT0 = 1.2 degC, f only needs to change from 0.73 to 0.82 to produce a 5 degC rise, or 0.92 for a 9 degC rise. Hence a value of the feedback factor, f, of 0.8+/-0.1 would be consistent with both current models and this paper. It would also indicate that climate sensitivity is at the top of expected range.
The analysis here is not dependent on whether CO2 injection from say volcanoes started the warming or CO2 was released and then amplified the warming from another initial source, and the paper offers both as possibilities.
The problem with rejiggering the climate models to show more sensitivity is that they will be in more trouble when it comes to explaining the current cooling.
Actually, the bigger problem would be that the carefully plotted synchronization between low CO2 and temps over the last millennium would go all meshugenah on them.
Was there a major sea movement 55 million years ago, like the Mediteranean filling up from the Atlantic fairly quickly? Wouldn’t such a sea movement churn up the CO2 from the bottom, causing a spike in atmospheric CO2?
As the event “passed” the calmer seas might re-sequester the CO2 fairly quickly, which would explain the spike up and then back down, as shown in the chart previously linked at:
http://img20.imageshack.us/img20/2464/tempvsco267m.png
Would such an even affect temperature, with the change of the water’s potential energy into kinetic?
(just the musings of a layman)
Oh dear, all your science chaps are doing it again. You’re looking at proxies and jiggling formulae when you should be seeking out direct evidence.
If we want to know what happened back then all we need to do is ask someone who witnessed it. Does anyone have Raquel Welch’s phone number?
Leif says:
Why indeed!?! I suppose that one can be an optimist like Smokey and imagine that this somehow means that the KNOWN radiative forcing due to a given change in greenhouse gases had nothing to do with the warming and there was some way more monstrous forcing around so that the climate sensitivity turns out to be rather small.
However, it is rather disturbing when most of the paleoclimate evidence seems to be pointing in the direction of a climate system that is more sensitive, not less sensitive, to perturbations!
Of course what happened 55 million years ago is relevant to present day and is as well known especially at the 150 years scale or even 5,000 y scale… we are in full delirium here.
Notwithstanding, the North Atlantic is barely existing, the Himalayas are still an ocean, and the Alps are just starting to be formed… Anyone with knowledge of atmospheric circulation must understand that this is a fundamentaly different pattern and aerological domains than those of todays, with consequences as to the climates experienced in various places.
So models cut off from the physical reality of meteorological phenomenons are as inept now than they are when applied to a 55million year old world. Who is reviewing these papers? Who is allowing that stuff to pass for science?
None of this matters.
It’s settled.
Al Gore simply wants global governance.
Denny (19:38:16) :
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
So, there must be something els out there to bite us, perhaps the AGW will turn out to be even worse than we thought…
How about this. Rising temperature causes an increase in CO2??? Duh.
Maybe Al Gore can start a company that profits from the anti global warming point of view. Maybe subsidies to Al Gore enterprises for new coal plants? The poor guy has only made a $100 mil on the GW scam. Give him a break.
The Herald Sun’s Andrew Bolt (on his website) has just accused al gore of lying on an interview with ABC telivision Australia.
The world at the time of the PETM looked dramatically different than the world of today. Different geographic locations for all land masses, different ocean systems. Apples and oranges.
They don’t need to adjust their models. They’ll just get NOAA to adjust the temperatures from 55 million years ago.
Now all they need to do is publish an article on how increased levels of CO2 actually suppress the mechanisms for measuring temperature and we are really 3 degrees warmer than what we thought we were.
moron (20:33:44) :
Cause Effect – Which is Which?
What comes first? Temp or Carbon?
A timely concept!
Also from wikipedia
On the other hand, there are suggestions that surges of activity occurred in the later stages of the volcanism and associated continental rifting. Intrusions of hot magma into carbon-rich sediments may have triggered the degassing of isotopically light methane in sufficient volumes to cause global warming and the observed isotope anomaly. This hypothesis is documented by the presence of extensive intrusive sill complexes and thousands of kilometer-sized hydrothermal vent complexes in sedimentary basins on the mid-Norwegian margin and west of Shetland [30][31]. Further phases of volcanic activity could have triggered the release of more methane, and caused other early Eocene warm events such as the ETM2.[10]
The methane caused the warming and the CO2 just resulted from its decay in the atmosphere.
We can’t assume CO2 caused any of the warming until we know what happened in the PETM. Until then what is cause and what is effect is just speculation.
Denny (19:38:16) :
Leif,
Read the last Paragraph! It…
Denny, the last paragraph is ambiguous. I think Leif is correct in his observation, if I correctly interpreted what he said. I have bolded the important words from the last paragraph of the article:
“Some feedback loop or other processes that aren’t accounted for in these models…”
A feedback loop, or creation of energy from nothingness; AGWers could well attribute the feedback loop to CO2 paranormal thermal powers.
The phrase “other processes” includes a wide range of situations, the desertification, for example.
This from physicsforums.com strikes me as plausible
Andre et al, (2006) Understanding the Paleocene Eocene Thermal Maximum, a reconstruction
Keywords Paleocene Eocene Thermal Maximum clathrate Pangea PETM
Abstract
The Paleocene Eocene Thermal Maximum is characterized by enigmatic proxy evidence suggesting warm climates, and, as inferred by numerous publications, massive marine methane hydrate (clathrate) destabilization events. The recent discovery of a near-tropical Arctic ocean however requires a review of existing hypotheses, including greenhouse forcing, to check for the trigger and the cause of events of the PETM.
Here we propose that alternately the same proxy evidence, in toto, could have been caused by another mechanism. After the breakup of the Pangaea supercontinent some 200 million years ago, North America moved in a semicircle clockwise towards the north, hinging around the Greenland – Svalbard area until Alaska and Beringia made contact. Thus the Arctic Sea became isolated and no longer had contact with open oceans. Then the evaporation of the Arctic inner sea exceeded accumulation for a prolonged period causing a significant sea level lowering in comparison with the rest of the oceans. Furthermore, the tectonic movements of the plates may have enlarged the Arctic basin as North America continued to move progressively to the southwest, lowering sea level iin the Arctic basin further.
At the start of the Eocene, 55 Ma ago, the Turgai Strait, splitting Siberia from North to South may have connected the virtually empty Arctic basin and the near-tropical Tethys sea, resulting in an Arctic basin which would have started to fill rapidly with the warm surface water of the Tethys sea, not only transporting alien biota towards the Arctic but also warming up the area. The resulting abrupt sea level drop of some 15-30 meters in a very short time would have caused a secular destabilization of the marine methane hydrates, which would then explain the remaining proxy evidence pertaining to isotope excursions and the Elmo. Hence the empty-Arctic-basin-hypothesis appears to be backed by the evidence, challenging the case for the Palaeocene Eocene Thermal Maximum to be explained primarily as an enhanced Greenhouse forcing scenario.
That’s how you get tropical algae at the North Pole