Warming in Last 50 Years Predicted by Natural Climate Cycles
by Roy W. Spencer, Ph. D.
One of the main conclusions of the 2007 IPCC report was that the warming over the last 50 years was most likely due to anthropogenic pollution, especially increasing atmospheric CO2 from fossil fuel burning.
But a minority of climate researchers have maintained that some — or even most — of that warming could have been due to natural causes. For instance, the Pacific Decadal Oscillation (PDO) and Atlantic Multi-decadal Oscillation (AMO) are natural modes of climate variability which have similar time scales to warming and cooling periods during the 20th Century. Also, El Nino — which is known to cause global-average warmth — has been more frequent in the last 30 years or so; the Southern Oscillation Index (SOI) is a measure of El Nino and La Nina activity.
A simple way to examine the possibility that these climate cycles might be involved in the warming over the last 50 years in to do a statistical comparison of the yearly temperature variations versus the PDO, AMO, and SOI yearly values. But of course, correlation does not prove causation.
So, what if we use the statistics BEFORE the last 50 years to come up with a model of temperature variability, and then see if that statistical model can “predict” the strong warming over the most recent 50 year period? That would be much more convincing because, if the relationship between temperature and these 3 climate indicies for the first half of the 20th Century just happened to be accidental, we sure wouldn’t expect it to accidentally predict the strong warming which has occurred in the second half of the 20th Century, would we?
Temperature, or Temperature Change Rate?
This kind of statistical comparison is usually performed with temperature. But there is greater physical justification for using the temperature change rate, instead of temperature. This is because if natural climate cycles are correlated to the time rate of change of temperature, that means they represent heating or cooling influences, such as changes in global cloud cover (albedo).
Such a relationship, shown in the plot below, would provide a causal link of these natural cycles as forcing mechanisms for temperature change, since the peak forcing then precedes the peak temperature.
Predicting Northern Hemispheric Warming Since 1960
Since most of the recent warming has occurred over the Northern Hemisphere, I chose to use the CRUTem3 yearly record of Northern Hemispheric temperature variations for the period 1900 through 2009. From this record I computed the yearly change rates in temperature. I then linearly regressed these 1-year temperature change rates against the yearly average values of the PDO, AMO, and SOI.
I used the period from 1900 through 1960 for “training” to derive this statistical relationship, then applied it to the period 1961 through 2009 to see how well it predicted the yearly temperature change rates for that 50 year period. Then, to get the model-predicted temperatures, I simply added up the temperature change rates over time.
The result of this exercise in shown in the following plot.
What is rather amazing is that the rate of observed warming of the Northern Hemisphere since the 1970’s matches that which the PDO, AMO, and SOI together predict, based upon those natural cycles’ PREVIOUS relationships to the temperature change rate (prior to 1960).
Again I want to emphasize that my use of the temperature change rate, rather than temperature, as the predicted variable is based upon the expectation that these natural modes of climate variability represent forcing mechanisms — I believe through changes in cloud cover — which then cause a lagged temperature response.
This is powerful evidence that most of the warming that the IPCC has attributed to human activities over the last 50 years could simply be due to natural, internal variability in the climate system. If true, this would also mean that (1) the climate system is much less sensitive to the CO2 content of the atmosphere than the IPCC claims, and (2) future warming from greenhouse gas emissions will be small.
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tonyb says: June 8, 2010 at 4:11 am
Clearly winters have become less cold through the last few centuries, hardly surprising as the LIA loosened its grip.
Hi Tony
I had a close look at the CETs summer-winter relationship and found something odd with records pre and post 1845. As an exercise I produced a short analysis.
Perhaps you could take a look, when you have some time to spare, and comment (if you whish by email).
http://www.vukcevic.talktalk.net/GWDa.htm
Since you are going public with that phrase, here’s a helpful tip: change “adverse” to “averse.”
Vuk
It looks interesting. I will email you separately
tonyb
I just started to read the hard copy of this report…..
http://www.economist.com/opinion/displaystory.cfm?story_id=15720419
This assumption is where the hotheads went wrong, way back when — they didn’t think of climate as fundamentally wobbly (variable from internal generated forcings), but as stable until forced. The climate record, pace the hockey stick, shows natural, unforced variability is the rule. Here are a few of a score of comments I’ve seen here on this topic:
Phlogiston also said:
He preceded that by:
Sphaerica says:
June 8, 2010 at 9:54 am
“So what you’ve done is to correlate, um, temperature to temperature. And you found a close correlation! Well done!”
Should read:
“So what you’ve done is to correlate, um, natural temperature cycles to current temperatures. And you found a close correlation! Well done!”
What he has shown is that the phasing of these natural cycles is such that they constructively interfere in recent times to produce at least a substantial portion of our current warming cycle. What we see in our limited field of view as a secular trend is, in fact, merely an isolated segment of a complex oscillation.
@Steve Garcia
‘The PDO, AMO and SOI are phenomena in themselves, driven essentially by the sun.’
Of course phenomenon, but I’d disagree driven essentially by the sun. I have come to understand that the oceans are driven by earth revolving around its own center in a yearly wobbly manner, the currents are created by the flat plateaus sticking up above em and endless mountain ridges below. And of course not to forget about the ever present man in the moon on his daily travels around and around always dragging the water mass’ with him. So then that would essentially be what creates all them oscillations. The Sun just heats the oceans around the equator which just adds to the chaos just like the cold desalinated but melting sea ice at the arctic adds to the chaos, but not essentially driving any ocean.
How much circulation would there really be if earth was stationary rock solid with no moon?
The trolls on parade today are demonstrating clearly why they will never understand climate:
1) They dont understand anything about dynamic chaos and spontaneous nonequilibrium pattern,
2) thus they are baffled at thought of internally generated oscillations;
3) They never did differential calculus at school so they dont understand the difference between absolute and relative values, and the idea of differential quantities;
4) They believe that pressure is a proxy for temperature
5) They believe the AGW establishment fabrication of climate history with all temperature variation pre-1950 air-brushed out, a MWP successfully “lost”,
6) They have no curiosity about the real world climate, believing only computer models built to force a falsified climate record into a predetermined AGW outcome.
Reasonable extrapolation of Dr Spencers model forward based on the PDO, AMO and SOI trends probably predicts a temperature downturn. A successful forward (as opposed to backward) climate prediction will also be something beyond their experience.
A decrease in cloud cover would do it — and that could be caused by all sorts of feedbacks and whatnot in a chaotic system (see above). Spencer’s book stresses the impact of natural variation in cloud-cover changes.
richard telford says:
June 8, 2010 at 2:39 am
“Since one might expect AGW to manifest itself by enhancing natural warm modes of climate variability, this analysis proves nothing.”
___________
I would tend to agree, though I can appreciate the good Dr.’s thoroughness of approach. We simply don’t know how AGW might be affecting and enhancing these natural cycles ocean heat equalization. If indeed, the bulk of the heat from AGW has gone into the ocean as the models indicate it has, then you’d expect some acceleration in the cycles. Dr. Spencer’s whole point seems to be about the rate of change of temperatures, and as discussed many times, the big event, or the big “shift” in that rate of change began during the “climate shift” of 76-77, of which much has been written, and not much resolved. We know the shift occurred, and we know ocean heat content had been rising prior, and pretty much ever since. The cause? Natural? AGW? A little of both?
Bart says:
June 8, 2010 at 11:20 am
What he has shown is that the phasing of these natural cycles is such that they constructively interfere in recent times to produce at least a substantial portion of our current warming cycle. What we see in our limited field of view as a secular trend is, in fact, merely an isolated segment of a complex oscillation.
I am shocked.
Changes in cloud cover do not offer an explanation for a cooling stratosphere. Stratospheric cooling has been cited as a “fingerprint” of anthropogenic greenhouse warming and as a phenomenon that does not occur from decreased cloudiness. Since this cooling is clearly observed it casts serious doubt on the viability of Dr. Spencer’s decreasing cloud cover model.
Sphaerica says:
June 8, 2010 at 9:54 am
Dr. Spencer,
Various web sites define these indexes as:
The PDO Index is calculated by spatially averaging the monthly sea surface temperature (SST) of the Pacific Ocean north of 20°N.
The Southern Oscillation Index (SOI) is calculated from the monthly or seasonal fluctuations in the air pressure difference between Tahiti and Darwin.
[Note that air pressure is dependent upon, and therefore a proxy for, temperature.]
The AMO signal is usually defined from the patterns of SST variability in the North Atlantic once any linear trend has been removed.
So what you’ve done is to correlate, um, temperature to temperature. And you found a close correlation! Well done!
Now kindly use this to predict future temperatures. Please extend your graph and your model to predict temperatures through the year 2060. Oh, wait, we have to wait until 2060 to do that, so that you have the temperature readings with which to predict the temperature readings.
Also, kindly explain the mechanism (other than hand waving, magic, and climate gremlins) that is actually causing the warming. You’ve described it. You’ve quantified it. You’ve “predicted” it based on a correlation to three temperature based indexes. But explain it. How does a planet with a relatively stable climate suddenly, dramatically warm?
——-
UHI effect ?
This is really funny:
dynamic chaos and spontaneous nonequilibrium pattern
Where chaos is found, chances are the trouble is ours not nature’s.
Non-equilibrium: I agree on that one! if self (auto)-anthropogenic.
They never did differential calculus at school LOL!
How do you think COMPUTERS solve such calculations?
By using the four elemental operations! Didn’t you know it?
That is the real problem of science now: The more complicated the more “intelligent”
Only a fool like Pitagoras could have only used a string (the monochord) to understand all laws of nature!
Who the fools are and who the sages . We live in interesting times, where everything should and will be revisited.
“GeoFlynx says:
June 8, 2010 at 11:45 am
Changes in cloud cover do not offer an explanation for a cooling stratosphere. Stratospheric cooling has been cited as a “fingerprint” of anthropogenic greenhouse warming and as a phenomenon that does not occur from decreased cloudiness.”
Controlling the message… “Fingerprinting” of course is a term chosen to create the association with a human fingerprint, like “only this human can have caused this fingerprint”.
Of course you know that it’s not that easy with temperatures. Something cools, as a GCM has predicted. Is the GCM now correct in all its projections? At the same time, the same GCM fails to correctly project temperatures in the tropical troposphere.
To put it simply: It could be coincidence, your stratospheric cooling. The GCM’s got one thing right. Way to go. Coincidence sounds much better than “Fingerprint” in my opinion.
rogerkni says:
June 8, 2010 at 11:31 am
Sphaerica says:
How does a planet with a relatively stable climate suddenly, dramatically warm?
A decrease in cloud cover would do it — and that could be caused by all sorts of feedbacks and whatnot in a chaotic system (see above). Spencer’s book stresses the impact of natural variation in cloud-cover changes.
——————————————————————————–
And yet, the idea I got from the days after 9/11/2001 was that cloud cover has increased markedly in the jet age….
Wren
To get some appreciation for “stable” climate see Easterbrook’sSHORT-TERM WARM/COOL CYCLES FROM THE GREENLAND ICE CORE
A scientific model may be effective in calculation without any understanding of the underlying physical cause. E.g. Newton developed his laws of gravity with no understanding or effort to “explain” gravity.
There are numerous physical causes together with chaotic fluctuations. Climate science is very new. One does not have to “explain” it fully to make major advances as Spencer is doing.
Sphaerica says:
June 8, 2010 at 10:21 am
Gail Combs,
Models however are NOT scientific facts and Dr. Spencer is not calling this “model” a fact.
And whom, anywhere, any when, has ever said that models, or any specific model, is a fact? You made that up.
You either believe it is appropriate to use models in science, or you believe it is inappropriate. So don’t dodge the question. Which is it?
_________________________________________________________________________
It is inappropriate to use models in science and use them to write “Summaries for Policymakers” It is inappropriate to use models in science and use them as the basis for a film designed to frighten children as well as adults. And it is certainly UNETHICAL to continue pushing those models down the throats of the world’s people, knowing they will devastate economics and ultimately lead to misery and death especially when you write in an e-mail:
“The fact is that we can’t account for the lack of warming at the moment and it is a travesty that we can’t,” Dr. Trenberth
The AGW climate models are the basis for the EU carbon trading and may soon be the bases for the Cap & Trade or EPA regulation of CO2. If those models are NOT being used as “fact” then what are they being used for??? Hype in the world’s most devastating hoax????
DirkH says:
June 8, 2010 at 12:16 pm
We can keep groping in the dark or dare viewing other explanations, like:
http://www.holoscience.com/news.php?article=9eq6g3aj
rogerkni says:
June 8, 2010 at 11:16 am
I see. So because a bunch of people talk about it on WUWT, it’s true? The world is quite simply too complex for man to understand, and all professional scientists were too dumb to recognize the complexity in the system? Everyone except for magically brilliant Dr. Spencer?
Wren says:
June 8, 2010 at 11:53 am
Hmmm. And how does that explain Dr. Spencer’s presentation of the lower tropospheric satellite readings here?
While I would personally disagree with Dr. Spencer as to whether the source of global warming is natural or anthropogenic, his recent thesis does acknowledge the existence of global warming as well as the general shape and condition of the “hockey stick” and the rise in global temperatures that it represents. Hopefully, this will put to rest the following:
1. The “Hockey Stick” controversy itself.
2. The shrinking cryosphere and decreasing Arctic ice.
3. The debate over rising sea levels due to thermal expansion and meltwater.
4. Changes in a warming biosphere – migration, vegetation, lizards, pine beetles etc.
“DirkH says:
June 8, 2010 at 12:16 pm
“GeoFlynx says:
June 8, 2010 at 11:45 am
Changes in cloud cover do not offer an explanation for a cooling stratosphere. Stratospheric cooling has been cited as a “fingerprint” of anthropogenic greenhouse warming and as a phenomenon that does not occur from decreased cloudiness.”
Controlling the message… “Fingerprinting” of course is a term chosen to create the association with a human fingerprint, like “only this human can have caused this fingerprint”. ”
Excuse me, i was annoyed by the word “Fingerprint”, i consider usage of such terms neurolinguistic programming or NewSpeak. Usually these terms are designed by PR agencies like futerra to control a debate.
When i said that GCM’s could by a pure stroke of luck have guessed the cooling of the stratosphere correctly i left open the justified question about why the stratosphere could be cooling, if cloud cover is not a reasonable explanation.
So i’ll just have a guess. CO2 is rising, that i don’t dispute, and it has a temporary warming effect, that much i acknowledge. And this will lead to a redistribution of energy and the surface temperature will warm slightly and the stratosphere will cool as guessed correctly by the GCM’s. Where i completely disagree with the GCM’s is the feedbacks. While the professionals assume large positive feedbacks i assume a net negative feedback (a negative feedback that is more negative than the standard negative feedback that is to be expected from the Stefan-Boltzmann law) in line with Ferenc Miskolczi’s theory. According to his theory, an increase in one GHG (CO2) must be compensated by a loss in another GHG (water vapor).
This net negative feedback has to result in an impossibility of the absolute level of CO2 being causative for the temperature anomaly but a possible causation of the temperature anomaly by the first derivative of the CO2 level, as the net negative feedback gives the system a high-pass characteristic. There is a lag time involved so over short periods the high pass characteristic will not be identified correctly. The last decade with it’s lack of warming could be a harbinger of this characteristic.
An according drop in humidity of the stratosphere has already been observed.
(and it hadn’t been projected by a GCM because they don’t incorporate Miskolczi’s theory)
http://www.scientificamerican.com/article.cfm?id=is-water-vapor-in-the-stratosphere-slowing-global-warming
phlogiston says:
June 8, 2010 at 11:24 am
You missed the point (why am I not surprised). It’s not possible for this model to predict temperatures, and any “successful forward climate prediction” as you call it is not possible with his model, because his inputs are the temperatures. His inputs are the PDO, AMO and SOI indexes, which can only be determined after they happen, and are themselves readings of sea surface temperatures.
His model has no predictive capability whatsoever. It’s like being able to predict the Dow Jones average using 3 well correlated, selected stocks. It’s of no value, because if you can’t predict those stocks, then you can’t predict the DJ average, so what’s the point? Worse yet, the stocks are themselves part of the Dow Jones, so what you’ve done is to say that you can predict an average by using some of the components used to ultimately compute the average; Accomplishing zero, but fooling a lot of wishlets into thinking they are seeing something magical, that shows them what they truly, truly want to believe.
All of you folks will agree that how a wonderful thing is having a big, big, carbon footprint, like eating, right now, a delicious and carbon polluting barbecue!