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.
<!– This entry was posted on Sunday, June 6th, 2010 at 6:51 AM and is filed under Blog Article. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed. –>
Rob Vermeulen,
“For what I see, the model has been trained on the 1900-1970 period, where actually anthropogenic contributions are believed to have been already high. So, to summarize, it really looks like you’re fitting a signal that already has more than “natural” variability.”
Although, the IPCC already concedes the early 20th century warming is mostly natural, you make a valid point. CO2 forcing could possibly be acting through the PDO, AMO and SOI, putting them in warm phases simultaneously and more frequently. However, if these three phenomena have this explanatory power, then what are we to make of climate model attributions and projections when those models don’t reproduce the multidecadal climate modes? The fallback position here, if this result is robust, like the fallback positions of Spencer’s other work and Lindzen’s work is that these are diagnostics that the models fail. With the models being the main “evidence” for high climate sensitivities and a net positive feedback to CO2 forcing, they do not need yet another correlated diagnostic failure. The failures to reproduce the increase in precipitation (Wentz) and the surface albedo feedbacks (Roesch) were quite enough.
As there seem to be two Alexanders replying, I have added K to Alexander as my identifier.
An excellent post. Took me a while to understand some of it – I struggle with acronyms and have to keep referencing them to remind myself of what they signify – but the climate alarmist agenda seems more and more to be based on a hunger to control and to profit rather than open and falsifiable science. I continue to maintain that warmth is good, extreme cold is anything but.
I came across a link to this paper (http://www.probeinternational.org/UPennCross.pdf) in the financial post. It is absolutely superb. It really drives a coach and horses through the idea of climate “science” showing that so much of the scientific “certainty” is blatant propaganda.
I would urge everyone to send a link to their political representatives and local media.
Since one might expect AGW to manifest itself by enhancing natural warm modes of climate variability, this analysis proves nothing.
Further, it is difficult to envisage a climate system that is very sensitive to internal forcing, but insensitive to external forcings.
I have been evaluating similar correlations for some time. What I have found is:
1. You will get the same result as presented by Dr. Spencer simply by doing a regression between the Hadcrut data and and the exponentially weighted moving average (EWMA) of the SOI. The EWMA requires a characteristic time of at least 10 years (i.e. the weighting of the most recent point, for monthly data, is 1/120).
2. There is also a similar correlation between the AMO and the SOI (using the same EWMA). Thus the AMO and SOI are not independent variables. The AMO is a lagged response to the SOI.
That global temperatures are correlated to a lagged response to the SOI clearly shows that the SOI is the forcing variable. In other words, atmospheric temperature is driven by sea surface temperatures.
Knowing that global atmospheric temperatures are a lagged response to sea surface temperatures, characterized by the SOI, and that the SOI has moderated over the past decade, indicates that global warming will moderate as well.
I have also tried to identify drivers for the SOI, but none are readily apparent. And while the SOI appears to cycle between warmer and colder trends lasting several decades, there does not appear to be a clear long term direction to the data.
James Sexton says: June 7, 2010 at 9:34 pm
“…….which then cause a lagged temperature response.”
I don’t understand why there would be a delay in response time. Don’t clouds respond as soon as they are formed?
Can’t speak for Dr Spencer but my understanding is that most of this would be measured in Ocean terms where the time lags are longer (and heat capacity greater) than those for land. The lag could be years for a reduction in OHC near the equator to reach the poles.
Not sure it is as simple as that. Models are useful for all kinds of reasons. The problem many here have with models, especially climate models, is the view of some that it is reality that needs refining not a particular model.
Research Project: Express your vote in a climate change debate!
Do you want to use a cutting-edge collective intelligence system to see a systematic summary of the Climate Change debate and express your vote? Participate in this research project.
The project, run by the Center for Collective Intelligence at the Massachusetts Institute of Technology, aims to develop novel collective intelligence technologies that enable more effective deliberation with large groups. We are looking for people interested in using our technology to browse and rate a “map” of the argument about Climate Change. Participation in the study is entirely voluntary, and all data will be anonymized, so your confidentiality is assured.
To get started, simply follow this link: http://franc2.mit.edu:8000/ci/register?E-3NNLOF-1375
Your participation is highly appreciated!
Mark says:
June 7, 2010 at 11:18 pm
What this model shows is that it is useful for this purpose, ie demonstrating the origin(s) of warming (some of). There is no model that can predict the climate. To predict climate it would have to predict every aspect of climate (PDO, AMO, etc) and that is absolutely impossible and anyone who claims differently is either a liar or a fool.
Climate models are not “models” in the scientific sense of the word. Atomic physics is founded on models, it has to be because we can’t see the atoms, but these models are subjected to detailed and persistent scrutiny. They are tested to their “limits” and when they fail, their failures are analysed and the model adjusted ‘mathematically’ and retested again and again. Physical models begin with a mathematical definition, are VV&T’ed, adjusted and VV&T’ed again until they agree PRECISELY with the known limits of reality. No climate model exists, to my knowledge, that has been through this exercise and therefore no climate model, in my opinion, has any useful predictive value.
Carlo says:
June 8, 2010 at 3:09 am
Is this so that your mediocre climate school can adjust it’s message to convince more of us that AGW is a valid science? or are you genuinely trying to engage in debate?
M77 says: June 8, 2010 at 12:45 am
Vukcevic, the correlation in the magnetic field intensity and arctic temp anomaly is way too good to be a coincidence.
I think there is a ‘somewhat remote’ possibility of a direct link between the geo-magnetic field and the AMO, with the GMF as driver with a degree of bidirectional feedback (work in progress).
PDO is more problematic, but there are tentative links there two, as I have shown here:
http://www.vukcevic.talktalk.net/LFC20.htm
However, it is often pointed out: correlation is not causation. Is it coincidence? Possible, but is it probable ?
My motto: ‘nature is adverse to a coincidence, it is ruled by a cause and the consequence’
I think that this graph supports the contention that the PDO is externally driven
http://astroclimateconnection.blogspot.com/2010/03/can-we-predict-when-pdo-will-turn.html
Dr. Spencer, I’m very appreciative of your work and contribution to this blog. But I continue to look for and have not found a survey of climate researchers that indicates what percentage believe the majority of warming during the last 50 years was due to anthropogenic pollution versus natural causes. Due you have such a reference? Or do you have some other objective method of determining the percentages? Otherwise, your opening statement “a minority of climate researchers” would show unsubstantiated bias.
This past weekend marked the first time northern Ohio had an EF4 tornado since the mid 1980s. Here is a recap of the tornado outbreak across northern Ohio this past weekend claiming 5 lives.
http://sabolscience.blogspot.com
Dr Spencer.
An interesting article.
I feel that in order to see distinct-although irregular-climate cycles it is useful to go as far back as possible and to home in on individual data sets that can be qualified, as opposed to relying on a single global temperature which is a composite record of very dubious provenance.
Here is my web site. It is called the Little Ice Age thermometers for a reason-it collects dozens of actual instrumental records from around the world, many of which were recording temperatures during much of the Little Ice Age.
http://climatereason.com/LittleIceAgeThermometers/
The oldest data set is from Central England which dates back to 1659. It clearly shows a very modest warming throughout its existence with the most notable upward slope being around 1700.
http://homepage.ntlworld.com/jdrake/Questioning_Climate/_sgg/m2_1.htm
The prime reasons for this modest increase in temperatures over the last 350 years can be seen in the next link. Clearly winters have become less cold through the last few centuries, hardly surprising as the LIA loosened its grip. So it would be more accurate to say that the UK has become less cold-due to warmer winters which have the greatest variance of any season-rather than become notably warmer overall.
http://www.climate4you.com/CentralEnglandTemperatureSince1659.htm
This sort of pattern of gentle warming for hundreds of years can be seen in my web site records, although the oldest ones are usefully collected here in Nicks’ old datasets.
http://i47.tinypic.com/2zgt4ly.jpg
http://i45.tinypic.com/125rs3m.jpg
Clearly the instrumental data available bears no relationship whatsoever to Michael Mann’s hockey stick which, instead of relying on actual instrumental records (and extremely good observation) believed that trees made better thermometers than thermometers.
http://en.wikipedia.org/wiki/Hockey_stick_controversy
If we extend the various graphs back through the ages we would be able to see the notable periods of warmth and cold that we can readily trace back at least 5000 years and we should view the unremarkable modern era in that context. I would assume that our period of natural warming will come to a halt at some point. Whether we are at that stage yet or not it is difficult to say. Certainly some parts of the world have shown little or no warming over the last few decades and some appear to be cooling. These are overwhelmed in the global records by a preponderance of warming stations (many in urban areas)
So it is easy to see that the climate changes over the years, but it would be very interesting if Dr Spencer could use his program to run the information from these old datasets and see what it tells us.
Tonyb
Dr. Spencer.
OK … so now we just need a mechanism for predicting the PDO, AMO, and SOI. I don’t doubt that these cycles affect the earth’s temperature, but the model you’ve come up with is just as useless as the GCMs that the Alarmists use, unless it can be made to have some sort of skill with regards to predicting future climate.
So the question stands, are you working on ways to predict these cycles in terms of directions and magnitude of change? Also … “publish”!!!
Some nice pics of the shuttle & ISS crossing our natural warming oven:
click1
click2
click3
[source]
Dr. Spencer,
Climate has yet to include mechanical factors such as rotational energies on an orb (which creates different areas of atmospheric climate), pressure, atmospheric friction, magnetics and centrifigal forces. I would include gravity but it is showing to be an electro-magnetic event.
Interestingly enough, most Ice Ages occur at the highest peak of gases produced which effects atmospheric interaction with the planets eco-system to lower gases by killing off plant and animal life that produce it.
So far scholars are showing that if “if it don’t include mathematics, it ain’t science”mentality.
I guess the key question in research now is: do scientists understand the SOI/PDO/AMO sufficiently to be able to predict their future oscillations?
Because if your conclusions are right, then temperature predictions depend on that.
And, I suspect, that SOI predictions may depend on solar parameters, the solar wind and certain functions of the atmosphere.
Not an easy set of predictions to be sure…….
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 what Anthony and I are showing here:
http://wattsupwiththat.files.wordpress.com/2009/05/figure6.png?w=510&h=300
I.e., the cycles are cycles of “temperature change rate.” When I get around to it, I plan to do a little simulation along the lines of what Roy posted up a few days ago on his blog about how random cloud changes can produce “excursions” in the “temperature change rate” comparable to what we see in the historical record. My idea is to take a simple sinusoidal model of a beat wave composed of 9 and 20 year cycles (the two main frequencies in the instrumental record of global temperature) and subject them to disturbances with a random variable having a standard deviation comparable to the standard deviation of monthly changes in the rate of change in global temperature.
As I said in my comments on Roy’s blog, I think the rate of change in temperature is composed of a “persistent” force from natural cycles of decadal and bidecadal (and possibly longer) length, and an “anti-persistent” tendency from random shocks to the system. That itself is not particularly profound. What is profound is showing — if it proves to be the case — that natural cycles with very modest parameters (the cycles shown in the link have amplitudes that could be explained by known variation in TSI), when subjected to random shocks of an order demonstrated in nature, can produce centennial (or longer) changes in global temperature on the order actually observed. I.e., it could be explained “naturally.” This is Roy’s insight, and I’m just thinking it through in terms and with reference to data I’m more familiar with.
Thx. Dr. Spencer. My questions would be: 1) how do we know there is no relationship btw GHG conc and those indicies (PDO, AMO, SOI)? 2) what are the outcomes of other obvious tests on the robustness of the approach (southern hemi? global? ) . Also, I enjoy your posts but it seems that your rarely ever come back to answer questions…additional discussion of the more critical questions would be greatly appreciated and would go a long way toward increasing credibility.
Are you making the point the EF4 tornadoes in Ohio should have been increasing in frequency during the last 25 years according to CAGW propoganda while in actuality they remain quite rare?
Sent from the southern end of tornado alley where we haven’t had an EF5 since 1997.
“the model wouldn’t account for an GHG-induced increase of the frequency of El Ninos, for example.”
This is verifiable, that GHG’s increase the frequency of El Ninos?
Smokey says:
June 8, 2010 at 4:37 am
Some nice pics of the shuttle & ISS crossing our natural warming oven:
Amazing. Also the pic at the top of this thread is remarkable, considering the subject matter of the post. Are we to take away the idea that the oceanic cycles are controlled by the sun and moon??
😉
Re David Holliday
IPCC claims most of the post 1970 warming is man-made (they mistaken it with warm PDO/AMO cycle, while both oscillations were known well before IPCC 2007 report, but never mind).
German IPCC-friendly climatologist Mojib Latif recently acknowledged the PDO influence ans stated, that 15 to 50?% of recent warming is attributable to PDO.
Me says that when we remove UHI or poor tropics record from HadCRUT, there is no warming remaining, attributable to CO2.
The big problem with any model is, few if any scientists know which are the leading factors and which are the lagging factors. Most skeptics believe (or can at least bring up) the fact (as I’ve seen it presented) that co2 lags temp by 800’ish years. This isn’t something a short term model can take in to consideration.
Besides, the earth needs us like a dog needs a flea.