I received an email-based interview request on climate a while back from Esquire Middle East. I have decided to include my whole response below. The questions they ask are nearly as informative as anything I say, as they betray that the editors of the publication have pretty much bought into not only global warming alarmism, but all the memes alarmists use to discredit skeptics. Its pretty clear all they know about the skeptic’s position is what they hear from alarmists about skeptics. Anyway, I responded to this from a hotel room in Kentucky and didn’t give it my best but I think it may be interesting to you. The questions are in bold, my answers in normal font.
Do you believe that global warming and climate change are a grave problem to the world at the moment ?
IF NO
What gives you reason to believe that global warming and climate change are not really happening?
I don’t deny they are happening, and neither do any other science-based skeptics. Alarmists like to tell the public that skeptics are taking these positions, in order to discredit them. The climate is always changing without any help from man — a good example is the drying up of North Africa over the last centuries. The period from 1600-1800 was among the coldest in the last 5000 years, so it is natural we would see warming in recovery from this.
Is there any scientific evidence to support that global warming and climate change is not really that harmful
I wrote a 90-minute presentation on this so it is hard to be brief. But here are a couple of thoughts1. I don’t deny greenhouse gas theory, that man’s CO2 can cause some incremental warming. The greenhouse gas theory has to be real, or the world would be much colder right now. No, what I deny is the catastrophe, that temperatures a hundred years hence will be five or ten degrees Celsius higher due to man’s co2
Interestingly, I think most everyone on the scientific end of the debate agrees that the direct warming from man’s Co2 acting alone will be relatively modest – on the order of a degree Celsius by the year 2100 according to the IPCC. Yeah, I know this seems oddly low — you never hear of global warming numbers as low as 1 degree — but it is actually a second theory, independent of greenhouse gas theory, that drives most of the warming. This second theory is that the climate is dominated by strong positive feedbacks that multiply the warming from CO2 many fold, and increase a modest 1 degree C of warming from man’s CO2 to catastrophic levels of 5 or even 10 degrees.
The example I use is to think of climate as a car. Co2 from man provides only a nudge to the car. The catastrophe comes from a second theory that the car (representing the climate) is perched precariously on the top of a hill with its brakes off, and a nudge from CO2 will start it rolling downhill until it crashes at the bottom.
When people say the science is settled, they generally mean greenhouse gas theory. But that means only the nudge is settled. What is far from settled is the second theory of strong net positive feedback in the climate, ie the theory the climate is perched on top of a hill. It is unusual for long-term stable but chaotic systems to be dominated by such strong positive feedbacks. In fact, only the most severe contortions allow scientists to claim their high-sensitivity models of catastrophic warming are consistent with the relatively modest warming of the past century.
2. The amount of unusual climate change we are seeing is GROSSLY exaggerated. We seem to be suffering under a massive case of observer bias in assessing any current effects of climate change. Extreme events, which have always existed, are used by both sides of the debate as supposed proof of long term global trends. But there is little useful we can learn about trends at the tails of the distribution, and it turns out that the means of key weather events in the US, from droughts to wet weather to tornadoes to hurricanes, show no meaningful trends.
We have this incredible hubris that by watching a chaotic system for about 20 years, we fully understand it. But climate has 30-year cycles, 200 year cycles, 1000-year cycles, etc. We don’t even know what is normal, so how can we say we are seeing things that are abnormal. We have seen a lot of melting sea ice in the Arctic, but we think we may have seen as much in the 1930’s, but we didn’t have satellites to watch the ice. And Antarctic Sea ice has been higher than normal while Arctic has been below normal.
Hurricanes are another great example. Al Gore swore that Hurricane Katrina was man-made, but it turns out there is actually a declining worldwide trend in hurricane and cyclone activity and energy, so much so that we hit the lowest level in 2009 since we started measuring by satellite 30 years ago.
Or take sea level rise. Sea levels are rising today and glaciers are shrinking. Sea levels are rising because they were rising in 1950 and in 1920 and in 1880 and in 1850. Sea levels have been steadily rising 1-3mm a year since about 1820 and the end of the little ice age. Ditto glacier retreat, which began around 1800 and has continued steadily to today, though the pace of retreat has slowed of late.
Imagine we wanted to look at customer visitation at a local restaurant that just closed after 60 years in business. If we watched for only a few hours, we might miss the huge variability of the crowds from early morning through each mealtime rush. Watch only for a day, and we might miss the seasonal variation, as vacationers pack the restaurant in March. Watch for just a year, and we might have missed the long, slow decline in visitation that eventually led to the restaurant closing. In climate, we are trying to decide if there is a long term decline at the restaurant after watching for the equivalent of only a few hours.
The reporting on whether manmade climate change is already happening is just awful. We see something happen that we can’t remember happening in the last 20 years and declare it to be “abnormal” and therefore “manmade.” Its absurd, and amazing to me that we skeptics are called anti-scientific when the science being practiced is so awful. The problem is that for academics, who are always scrambling for funds, climate change has become the best source of money. So you can’t just say you are studying acne, you have to say you are studying the effect of manmade climate change on acne. Essentially, we have told the academic world that they can get much more money for their work if they claim to see climate change. So is it any surprise they find it under every rock?
Are most scientists wrong?
I find judging science by counting scientists to be unproductive, so I have no idea. I will say that a lot of folks who sign petitions in support of the alarmist position have not really looked carefully at the science, they are merely showing support because they have been told skeptics are a bunch of religious fundamentalist anti-science types, so they want to express their support for science. It is ironic, as we found in the Climategate emails, that in fact they are supporting bad science, a small core group of scientists who have resisted normal scientific process of sharing data and replication
For some reason, we love to scare ourselves. Or, more likely, many people, particularly younger folks, like to feel that there is some way they can save the world, to deal with their own feelings of insignificance. And one can’t save the world unless it is in crisis. Every generation has these crises, and they are almost always overblown. Look at Paul Ehrlich — he has been wrong about 20 times. He said a billion people would die of starvation by 1980. He is just about never right, but people still lap up every thing he says. Because folks like him give people a sense of mission. And when you demonstrate to them that there is no crisis, they are not relieved (as one would expect someone to be when they find a crisis does not exist) — they are angry that you took their mission away from them.
What do you think is causing temperature changes on a scale never seen before?
Wow, you really are brainwashed. You have an assumption that we are seeing temperature changes on a scale never seen before, and so skeptics must start from this. But in fact the runup in temperatures from 1978-1998 that is the main “proof” of global warming is similar in scale and slope and duration to at least two other temperature increases between 1850 and 1950 which most definitely were not of anthropogenic origins. See here: http://www.climate-skeptic.com/2010/03/oh-maybe-ocean-occilations-are-important.html. There are many issues with which reasonable people can disagree, but your contention about temperature increases being unprecedented is simply wrong and accepted as wrong by about everyone.
What did you think to the results of Copenhagen?
*shrug* Copenhagen had little to do with climate and was much about lesser developed nations trying to extract money from wealthier nations. Climate was just a pretext — do you really think Robert Mugabe or Hugo Chavez care about climate change?
Why do governments seem so concerned with the issue?
The fear of man-made catastrophic climate change gives government officials their best leverage since the repudiation of communism to substantially increase the power of themselves and their government.
If fossil fuels will run out anyway, surely we should move to find alternatives. Why not now?
You are welcome to. Entrepreneurs around the world have been trying to do so for decades. Wealth beyond measure is there for the person or company who is able to do it. What are you going to do to speed it up if such a huge incentive already exists? The government sometimes feels like it can just have its way and wish things into being. It never works.If the technology is not ready, no amount of government prodding or mandating will make it ready. All we will get is more wasted spending and more dead-end technology investments and more public funds poured into the hands of the politically connected. Why hurry if we are not ready? There are still fossil fuels for decades. Why increase the costs to every consumer to hurry this transition to no purpose?
There are perhaps a billion people in the world, particularly in Asia, on the verge of emerging from poverty. They are only able to do so by burning every fossil fuel they can get their hands on. The alternatives that exist today are rich people’s toys, expensive sources of power that we can afford because they ease our guilt somehow. The poor don’t have this luxury.
Even if it is not guaranteed that manmade emissions are to blame, wouldn’t it be wise to act anyway? It’s a hell of a gamble to our children’s future.
Should we spend a trillion dollars on space lasers in case of an alien invasion of Earth? Why not, its a hell of a gamble to our children’s future. We can’t go pre-emptively fix every low-probability problem just because someone claims it might be a catastrophe. Why fix a hypothetical environmental problem when there are 10 other real ones impacting people today that we are ignoring.
The statement you are making only makes sense if the transition if free or low cost. But substantially eliminating fossil fuel use is tremendously expensive. In fact, it is more expensive at this point with current technology than anything the world has ever done. Folks who claim the costs are low are either ignorant or lying. Every major economy will see trillions of dollars of lost output. But forget the rich nations. Remember the billion people emerging from poverty. Strong world action will essentially consign these people to stay in poverty. Do you want your kids 1 degree cooler at the cost of putting a billion people into poverty? It is not the simple question you make it out to be.
Don’t we have a duty to protect or planet for future generations?(i.e. save it from deforestation, pollution etc)
Sure, but as I stated above, we have all kinds of duties to future generations, and not all of them have to do with the environment. But I would argue that the current obsession with small changes to trace levels of CO2 in the atmosphere has in fact gutted the environmental movement. Nothing else is getting done. Take deforestation. My personal interest is in protecting wilderness, and my charity of choice is land trusts that preserve the Amazon. But do you know the #1 cause of deforestation in the Amazon over the last decade? It was the Brazilian ethanol program, which is supposed to be fighting CO2, but now has been shown to do little or nothing for CO2 and it is incentivizing farmers to clear the Amazon to plant more switchgrass and other ethanol crops. Ditto in the US, where ethanol programs are raising food prices and adding to deforestationI would argue that CO2 is not even in the top 10 worst environmental problems in the world. Take clean water in Africa, which I do consider a top 10 problem. The only way Africans are going to get clean water is from using cheap energy to pump and treat water, cheap energy whose only really realistic source is from fossil fuels.
My prediction– 10-20 years from now, environmentalists are going to look back on the current global warming hysteria as the worst thing ever to happened to the environmental movement.
Further comments
Again, this is very off the cuff. I really delve into the science here: http://www.climate-skeptic.com/2010/01/catastrophe-denied-the-science-of-the-skeptics-position.html
SOME CONCLUDING THOUGHTS
OK, so every one of these questions are probing – they are hitting at perceived weaknesses in the skeptic’s position. Fine, it is good when the media is critical. But compare the questions above to the total softballs lobbed at alarmists.
IF YES
How bad is climate change at the moment?
What did you think to the results of Copenhagen?
Is it increasing at an uncontrollable rate? Or is there still a chance to reduce climate change and alter its predicted course of events?
Do you have any comments on the recent e-mail leak scandal that was publicized?
What do you think about the rising levels of climate change skepticism?
How could and/or will climate change or similarly global warming affect the Middle East region in particular the Arabian peninsula?
What about other vulnerable countries?
What can the average citizen do more or less to help reduce climate change and its impact?
What do you predict will happen to major cities in the world if the problem of global warming is not addressed immediately?
How will an increase in global warming change the earth’s natural weather activities i.e. how will people and animals be affected, ecosystems, the weather….
How can we move forward on this issue?
Are you confident we can find a solution?
What are the chances of a new technology saving us? (for example, carbon capture)
Is carbon trading effectively passing the buck? Does it actually help
Only one is arguably critical — the one about the CRU emails — and look at the softball way in which it is asked. The journalists here make no secret of which side they are one.
Ahh, yes… Knew the infantile stab at my family would be forthcoming from the Troll. Predictable. Didn’t anyone ever teach you that if you have to resort to name-calling and ad hom you are losing the argument? Guess not.
I’m suprised you didn’t start with “yo mama” jokes, but I have a feeling that you grew up in AUS/NZ or GB and they really don’t have those kind of jokes there. (BTW, my wife is Auzzie which is where I’m betting you are from too, but honestly, it doesn’t matter whether you are or not. I don’t really care, and if I am right, I expect you’d lie anyway.)
And yes, it was a “you” as in “you all” or more appropriately, “y’all”. ;P
And the point still stands. You are denying (lamely) that global climate is -basically- cyclical in nature, made up of various other NATURAL cycles with extreme events interspersed. (like an asteroid strike, or super volcano.)
These cycles create a measure of equalibrium and are dominated by mostly negative feedbacks. (As is most EVERYTHING in the physical universe) Examples of these cycles include, but are not limited to:
-The Schwabe solar cycle (11yr)
-The Hale Solar Cycle (22yr)
-The Gleissberg Solar cycle (87yr)
-The de Vries solar cycle (210yr)
-The Hallstatt solar cycle (2300yrs)
-A possible 6000yr solar cycle (unnamed) (ref:http://www.springerlink.com/content/v856256j65142l48/)
-Cycles in Solar wobble
-The Milankovitch Cycle (ref:http://en.wikipedia.org/wiki/File:Milankovitch_Variations.png)
-The carbon Cycle
-The Biogeochemical Cycle
-The Pacific Decadal Oscillation (The big word on the end means “Cycle”)
-The North Atlantic Oscillation
-Thermohaline Ciriculation cycles
(ref:http://holocene.meteo.psu.edu/shared/articles/KnightetalGRL05.pdf)
-Volcanic Cycles
(ref:http://volcanoes.usgs.gov/yvo/about/history/cycles.php)
I could go on, but there is no point. By trying to say that there are no cycles in climate (or Solar physics for that matter), you just look plain ignorant.
Doc
Here, I’ll save Hunter the trouble:
-The Schwabe solar cycle (11yr)—WRONG!
-The Hale Solar Cycle (22yr)—WRONG!
-The Gleissberg Solar cycle (87yr)—WRONG!
-The de Vries solar cycle (210yr)—WRONG!
-The Hallstatt solar cycle (2300yrs)—WRONG!
-A possible 6000yr solar cycle (unnamed) (ref:http://www.springerlink.com/content/v856256j65142l48/)—WRONG!
-Cycles in Solar wobble—WRONG!
-The Milankovitch Cycle (ref:http://en.wikipedia.org/wiki/File:Milankovitch_Variations.png)—WRONG!
-The carbon Cycle—WRONG!
-The Biogeochemical Cycle
-The Pacific Decadal Oscillation (The big word on the end means “Cycle”)—WRONG!
-The North Atlantic Oscillation—WRONG!
-Thermohaline Ciriculation cycles—WRONG!
(ref:http://holocene.meteo.psu.edu/shared/articles/KnightetalGRL05.pdf)
-Volcanic Cycles—WRONG!
(ref:http://volcanoes.usgs.gov/yvo/about/history/cycles.php)
ALL WRONG YOU FUCKWIT!
BargHumer:
So, let me get this right, one side says the planet is in dire peril and the other says no, the consequences of trying to save the planet in dire peril will put millions of people in dire peril. Such an important watershed moment in world history yet all the blogging “experts” would rather engage in mud wrestling. Perhaps Nero’s higher priorities were justifiable after all.
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That is the discredited “precautionary principal”.
There are many perils much more likely and much more damaging than than global warming and it only makes sense to take care of them first.
A meteor/asteroid/comet large enough to cause a nuclear winter will impact the earth. The only unknown is the date. This is as certain as anything can possibly be.
Building a small number of spaceships with the required equipment to turn aside such meteors is so cheap it is almost free and yet it hasn’t been done ? Why not ? Because the “precautionary principal ” is used as a tool when logic fails.
The climate alarmists might be right so we must spend tens of trillions of dollars ! Nonsense !
The “precautionary principle”(PP) seems to have been enshrined in European law. The burden of proof that any action to reduce one risk does not itself cause harm, falls on those “taking action” (Wiki).
If this “PP” is discredited, it is hard to see how it has become law. On the other hand it is hard to see how it can be applied since those taking action also bear the burden for proving that such action will not harm anyone.
In the case of AGW, the “harm” that reductions in CO2 will cause continue to be ignored by those advocating the action. “PP” may be discredited but only because of the misinterpretation of it by those who seek to use it for their own ends.
In the case of a large meteor heading for Earth, ignoring the likely destruction of a continent may be justified in order to save the planet. Scientific consensus would be necessary that a direct hit is imminent, but wouldn’t that consensus be undermined by the scientists living on the doomed continent? Can a scientific consensus ever be truly scientific? I don’t think so.
Ha ha ha, you still think the carbon cycle means “carbon varies cyclically”! You really think that all you have to do is list things with the word “cycle” in, and that will prove that each and every climate influence varies in an easily parametrised periodic fashion. Well, why not carry on? Water cycle! CNO cycle! Carnot cycle! Menstrual cycle! Ring cycle! My god, everything is cyclic! And therefore, CO2 does not cause global warming!
What a despicable cunt you are. You have not got even the faintest idea about how the climate works. You are mentally ill-equipped to understand science. Why don’t you just fuck off and leave it to those who have the intellect to grasp the basics? Your input is irrelevant, tiresome and disastrously ill-informed.
@hunter(the pathetic troll),
You should continue this forever. You should keep this up- on your own you are helping people see that CAGW extremism results in terrible personality disorders and loss of intelligence.
But in your case, maybe there was not much to lose?
Keep up the great support of the skeptical cause by way of demonstration.
The “precautionary principle”(PP) seems to have been enshrined in European law. The burden of proof that any action to reduce one risk does not itself cause harm, falls on those “taking action” (Wiki).
BargHumer
If this “PP” is discredited, it is hard to see how it has become law. On the other hand it is hard to see how it can be applied since those taking action also bear the burden for proving that such action will not harm anyone.
[ It is discredited because it is invoked only by those who can’t prove actual harm. (Hence precautionary ) The second pert is also interesting. Spending tens of trillions of dollars on CO2 reduction is clearly harmful. The question is the supposed benefits.– NetDr]
In the case of AGW, the “harm” that reductions in CO2 will cause continue to be ignored by those advocating the action. “PP” may be discredited but only because of the misinterpretation of it by those who seek to use it for their own ends.
[PP is not practical because of the large number of problems facing mankind and the limited resources we have at our disposal to solve them. We must pick our battles wisely. — NetDr]
In the case of a large meteor heading for Earth, ignoring the likely destruction of a continent may be justified in order to save the planet. Scientific consensus would be necessary that a direct hit is imminent, but wouldn’t that consensus be undermined by the scientists living on the doomed continent? Can a scientific consensus ever be truly scientific? I don’t think so.
[I am not saying to wait until a meteor has been spotted I am suggesting building the ships long before one has been detected in the theory that we can never be 100 % certain that we have seen all possible objects. That is where the PP comes in. Just a few years ago a rather large chunk of iron passed between the earth and the moon and wasn’t detected until it was past us. The PP specifies that the harm be unproven or it is not precautionary any more. — NetDr]
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As far as “green jobs” are concerned, unless there is an actual problem they are make work.
We could hire 100,000 people to dig holes and 100,000 more to fill them in. We could pay each of our workers $100,000 and the economy and taxes would go crazy.
We could be the world leader in hole theory and could grant PhD’s in Hole. The best and brightest students would go into hole theory and to heck with curing cancer.
Or you could just listen to the experts…oh I forgot, you all are experts. Well, perhaps you’d like to prove the good folks at Real Climate wrong?
The lure of solar forcing
Filed under:
— gavin @ 15 July 2005
It’s obvious.
The sun provides 99.998% of the energy to the Earth’s climate (the rest coming from geothermal heat sources). The circulation patterns of the tropical Hadley Cell, the mid latitude storm tracks the polar high and the resulting climate zones are all driven by the gradients of solar heating as a function of latitude. So of course any significant change to solar output is bound to affect the climate, it stands to reason! Since we can see that there are changes in solar activity, it’s therefore just a question of finding the link. Researchers for over a century have therefore taken any climate records they can find and searched for correlations to the sunspots, the solar-cycle length, geomagnetic indices, cosmogenic isotopes or smoothed versions thereof (and there are many ways to do the smoothing, and you don’t even need to confine yourself to one single method per record). At the same time, estimates of solar output in the past are extremely uncertain, and so there is a great deal of scope in blaming any unexplained phenomena on solar changes without fear of contradiction.
Astute readers will notice that there is a clear problem here. The widespread predisposition to believe that there must be a significant link and a lack of precise knowledge of past changes are two ingredients that can prove, err…., scientifically troublesome. Unfortunately they lead to a tendency to keep looking for the correlation until one finds one. When that occurs (as it will if you look hard enough even in random data) it gets published as one more proof of the significant impact that solar change has on climate. Never do the authors describe how many records and how many different smoothing methods they went through before they found this one case where the significance is greater than 95%. Of course, if they went through more than 20, the chances of randomly stumbling onto this level of significance is quite high.
The proof that this often happens is shown by the number of these published correlations that fall apart once another few years of data are added, cosmic rays (which are modulated by solar activity) and cloudiness for instance.
Sometimes even papers in highly respected journals fall into the same trap. Friis-Christensen and Lassen (Science, 1991) was a notorious paper that purported to link solar-cycle length (i.e. the time between sucessive sunspot maxima or minima) to surface temperatures that is still quoted widely. As discussed at length by Peter Laut and colleagues, the excellent correlation between solar cycle length and hemispheric mean temperature only appeared when the method of smoothing changed as one went along. The only reason for doing that is that it shows the relationship (that they ‘knew’ must be there) more clearly. And, unsurprisingly, with another cycle of data, the relationship failed to hold up.
The potential for self-delusion is significantly enhanced by the fact that climate data generally does have a lot of signal in the decadal band (say between 9 and 15 years). This variability relates to the incidence of volcanic eruptions, ENSO cycles, the Pacific Decadal Oscillation (PDO) etc. as well as potentially the solar cycle. So another neat trick to convince yourself that you found a solar-climate link is to use a very narrow band pass filter centered around 11 years, to match the rough periodicity of the sun spot cycle, and then show that your 11 year cycle in the data matches the sun spot cycle. Often these correlations mysteriously change phase with time, which is usually described as evidence of the non-linearity of the climate system, but in fact is the expected behaviour when there is no actual coherence. Even if the phase relationship is stable, the amount of variance explained in the original record is usually extremely small.
This is not to say that there is no solar influence on climate change, only that establishing such a link is more difficult then many assume. What is generally required is a consistent signal over a number of cycles (either the 11 year sunspot cycle or more long term variations), similar effects if the timeseries are split, and sufficient true degrees of freedom that the connection is significant and that it explains a non-negligible fraction of the variance. These are actually quite stiff hurdles and so the number of links that survive this filter are quite small. In some rough order of certainty we can consider that the 11 year solar cycle impacts on the following are well accepted: stratospheric ozone, cosmogenic isotope production, upper atmospheric geopotential heights, stratospheric temperatures and (slightly less certain and with small magnitudes ~0.1 deg C) tropospheric and ocean temperatures. More marginal are impacts on wintertime tropospheric circulation (like the NAO). It is also clear that if there really was a big signal in the data, it would have been found by now. The very fact that we are still arguing about statisitical significance implies that whatever signal there is, is small.
Over the multi-decadal time scales, there is more reasonable evidence for an NAO and surface temperature response to solar changes though the magnitudes are still small. Over even longer time scales (hundreds of years) there are a number of paleo-records that correlate with records of cosmogenic isotopes (particularly 10Be and 14C), however, these records are somewhat modulated by climate processes themselves (the carbon cycle in the case of 14C, aerosol deposition and transport processes for 10Be) and so don’t offer an absolutely clean attribution. Nonetheless, by comparing with both isotopes and trying to correct for climate (and geomagnetic) effects, some coherent signals have been seen.
Some contrarian commentators have recently fallen into the habit of mass mailing any new solar-related abstracts and implying that the existence of solar forcing in the past negates any possible recent anthropogenic impact on climate. Since these studies do not have any implication for the radiative impact of CO2, and don’t change the fact that there has been no effective change in any solar indices since about 1950, it is hard to see a substantial basis for this (implied) argument. For instance, there has been a lot of recent attention paid to Mangini et al. (2005) where a solar link to a new Alpine speleothem record was claimed. However, a quick analysis (right) indicates that the explained variance in the record (smoothed over 25 years) correlated to the 14C-production function (a slightly cleaner solar proxy than the resdiual atmospheric 14C (Muscheler et al, 2005 – see comment/link below)) is only about 5%. Hardly a definitive refutation of anthropogenic greenhouse gas forcing.
A more interesting question is whether our current understanding of how solar forcing works is sufficient to explain the clearest solar impacts in the record. During the most studied period, the Maunder Minimum (MM) in the late 17th Century, sunspots were very rarely seen and that corresponded to a particularly cool period in the Northern Hemisphere (particularly in Europe as is seen in the speleothem record as well – NB. cooler temperatures are associated with increased isotope ratios). In order to assess that, all other forcings that were operating at the same time need to be considered as well. The MM was also a time of enhanced volcanic activity, and the cooling from this was probably comparable with the cooling due to solar effects (an exact attribution is impossible given the uncertainties in both forcings) .Another important factor is that the records of cooling at the MM are predominantly continental and mainly located in North America and Eurasia. This is consistent with the eveidence for a weak NAO at this time in independent reconstructions.
So can models using what we are reasonably sure of match these results? The answer is probably (us climate scientists always need to hedge!). Using the known amplification of the solar cycle (and presumably the long term trend) in the UV band, allowing stratospheric temperatures and circulation patterns to adjust and including the direct radiative forcings from the sun and volcanoes, we found that it gave temperature anomalies and spatial patterns that were in fair agreement with the observations (Shindell et al, 2003). To be sure, there is still some wiggle room – but within the uncertainties in climate sensitivity, the magnitude of the long term trend in the solar forcing and the error bars in the temperature reconstructions, the model-data fit is quite good. Should those error bars be revised in the future, that conclusion might have to be revisited, but as things stand there is no obvious discrepency that requires some new exotic physics to explain it. That doesn’t mean that there isn’t some other mechanism we haven’t thought of yet, but it does mean that you can’t claim that there must necessarily be such a mechanism.
In summary, although solar forcing is real, the implications of that are often rather overstated. Since there has been a clear history of people fooling themselves about the importance of solar-climate links, any new studies in the field need to be considered very carefully before conclusions are drawn, especially with respect the warming over recent decades, which despite all of this discussion about solar activity, is almost all related to anthropogenic greenhouse gases.
Update (Jul 24): Upon further investigation, it appears that the archived age model for the speleothem (cave record) from Mangini et al (2005) is the version that has been tuned to maximise the correlation to the Delta 14C record they used. Thus any correlation with the 14C production record I used (since it is different) will be minimised. This actually makes it very difficult to assess how significant any particular correlation is (a perennial problem in solar-climate studies) – ideally you would probably want to sub-sample the distribution and see how big a correlation you could get from wiggle matching random data (within the limits of the few measured dates). Thus, my contention that solar doesn’t explain much of the variability in this record isn’t valid. It could explain anything from 5 to 40% (with unknown error bars). Sorry for any confusion.
“Never do the authors describe how many records and how many different smoothing methods they went through before they found this one case where the significance is greater than 95%. Of course, if they went through more than 20, the chances of randomly stumbling onto this level of significance is quite high.
The proof that this often happens is shown by the number of these published correlations that fall apart once another few years of data are added, cosmic rays (which are modulated by solar activity) and cloudiness for instance.”
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Sounds exactly like our broken climate models.
I know a man that studied old racing forms and when he thought he had found a patten he ran a model of it until the model made money. [In the past]
When he tried to make money in the present the model didn’t work. He then redid the models and tried again. Again it didn’t work.
The models are like driving a car looking in the rear view mirror. When the road turns, as it did, you crash.
“Astute readers will notice that there is a clear problem here. The widespread predisposition to believe that there must be a significant link and a lack of precise knowledge of past changes are two ingredients that can prove, err…., scientifically troublesome.”
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And yet that is exactly what the CO2 mafia does time and again. All temperature changes are caused by CO2, the trick is to find out how. [The irony is too delicious.The pot is calling the kettle black ?]
This is the new scientific method pioneered by Dr Mann.
They have a hypothesis and try to prove that it is true, which is backwards. The real scientific method is to try to prove that it is false. Dr Mann is the poster child for the new method. He cherry picked his data and massaged it with software that found hockey sticks in “red noise”
Waldy brought up the Mann-Wegamn dispute.
To summarize, Mann created the “hockey stick” using non-centered Principal Component Analysis. McIntyre and McKittrick, and later Wegman, stated
that Mann’s use of non-centered Principal component Analysis was flawed, and that the algorithm in effect was “searching for hockey sticks”.
Mann et al at “realclimate”, on January 6, 2005, stated that McIntyre and McKittrick were mistaken, and cited “Jolliffe” as an authority on PCA, stating that
non-centered PCA was a valid procedure.
Tamino later posted a series on “PCA” on his blog, “Open Mind”. Part 4 was posted on March 6, 2008. In this posting he asserted that
non centerd PCA was perfectly okay, stating,
” You shouldn’t just take my word for it, but you should take the word of Ian Jolliffe, one of the world’s foremost experts on PCA…”
Finally there’s a reply from Ian Jolliffe himself, who in effect said McIntyre and McKittrick’s criticism was correct, and Mann’s hockey stick
was based on dubious statistics.
From the January 6, 2005 “realclimate” post,
http://www.realclimate.org/index.php/archives/2005/01/on-yet-another-false-claim-by-mcintyre-and-mckitrick/
“6 Jan 2005
On Yet Another False Claim by McIntyre and McKitrick”…
“McIntyre and McKitrick (MM), in one of their many false claims regarding the Mann et al (MBH98) temperature reconstruction, assert that the “Hockey Stick” shape of the reconstruction is an artifact of the “non-centered” Principal Components Analysis (PCA) convention used by MBH98 in representing the North American International Tree Ring Data Bank (ITRDB) data series. “…
“Contrary to MM’s assertions, the use of non-centered PCA is well-established in the statistical literature, and in some cases is shown to give superior results to standard, centered PCA. See for example page 3 (middle paragraph) of this review. For specific applications of non-centered PCA to climate data, consider this presentation provided by statistical climatologist Ian Jolliffe who specializes in applications of PCA in the atmospheric sciences, having written a widely used text book on PCA. In his presentation, Jollife explains that non-centered PCA is appropriate when the reference means are chosen to have some a priori meaningful interpretation for the problem at hand.” ….
On March 6, 2008, “Open Mind” defended Mann’s hockey stick.
http://tamino.wordpress.com/2008/03/06/pca-part-4-non-centered-hockey-sticks/
“First let’s dispense with the last claim, that non-centered PCA isn’t right. This point was hammered by Wegman, who was recently quoted in reader comments thus:
“The controversy of Mann’s methods lies in that the proxies are centered on the mean of the period 1902-1995, rather than on the whole time period. This mean is, thus, actually decentered low, which will cause it to exhibit a larger variance, giving it preference for being selected as the first principal component. The net effect of this decentering using the proxy data in MBH and MBH99 is to produce a “hockey stick” shape. Centering the mean is a critical factor in using the principal component methodology properly. It is not clear that Mann and associates realized the error in their methodology at the time of publication.”
Just plain wrong. Centering is the usual custom, but other choices are still valid; we can perfectly well define PCs based on variation from any “origin” rather than from the average. It fact it has distinct advantages IF the origin has particular relevance to the issue at hand. You shouldn’t just take my word for it, but you *should* take the word of Ian Jolliffe, one of the world’s foremost experts on PCA, author of a seminal book on the subject. He takes an interesting look at the centering issue in this presentation.”
And finally we get a reply from Jolliffe himself:
http://tamino.wordpress.com/2008/08/10/open-thread-5-2/#comment-21873
“Ian Jolliffe // September 8, 2008 at 9:36 am
Apologies if this is not the correct place to make these comments. I am a complete newcomer to this largely anonymous mode of communication. I’d be grateful if my comments could be displayed wherever it is appropriate for them to appear.
It has recently come to my notice that on the following website, related to this one, my views have been misrepresented, and I would therefore like to correct any wrong impression that has been given.
http://tamino.wordpress.com/2008/03/06/pca-part-4-non-centered-hockey-sticks/
An apology from the person who wrote the page would be nice.
In reacting to Wegman’s criticism of ‘decentred’ PCA, the author says that Wegman is ‘just plain wrong’ and goes on to say ‘You shouldn’t just take my word for it, but you *should* take the word of Ian Jolliffe, one of the world’s foremost experts on PCA, author of a seminal book on the subject. He takes an interesting look at the centering issue in this presentation.’ It is flattering to be recognised as a world expert, and I’d like to think that the final sentence is true, though only ‘toy’ examples were given. However there is a strong implication that I have endorsed ‘decentred PCA’. This is ‘just plain wrong’.
The link to the presentation fails, as I changed my affiliation 18 months ago, and the website where the talk lived was closed down. The talk, although no longer very recent – it was given at 9IMSC in 2004 – is still accessible as talk 6 at http://www.secamlocal.ex.ac.uk/people/staff/itj201/RecentTalks.html
It certainly does not endorse decentred PCA. Indeed I had not understood what MBH had done until a few months ago. Furthermore, the talk is distinctly cool about anything other than the usual column-centred version of PCA. It gives situations where uncentred or doubly-centred versions might conceivably be of use, but especially for uncentred analyses, these are fairly restricted special cases. It is said that for all these different centrings ‘it’s less clear what we are optimising and how to interpret the results’.
I can’t claim to have read more than a tiny fraction of the vast amount written on the controversy surrounding decentred PCA (life is too short), but from what I’ve seen, this quote is entirely appropriate for that technique. There are an awful lot of red herrings, and a fair amount of bluster, out there in the discussion I’ve seen, but my main concern is that I don’t know how to interpret the results when such a strange centring is used? Does anyone? What are you optimising? A peculiar mixture of means and variances? An argument I’ve seen is that the standard PCA and decentred PCA are simply different ways of describing/decomposing the data, so decentring is OK. But equally, if both are OK, why be perverse and choose the technique whose results are hard to interpret? Of course, given that the data appear to be non-stationary, it’s arguable whether you should be using any type of PCA.
I am by no means a climate change denier. My strong impressive is that the evidence rests on much much more than the hockey stick. It therefore seems crazy that the MBH hockey stick has been given such prominence and that a group of influential climate scientists have doggedly defended a piece of dubious statistics. Misrepresenting the views of an independent scientist does little for their case either. It gives ammunition to those who wish to discredit climate change research more generally. It is possible that there are good reasons for decentred PCA to be the technique of choice for some types of analyses and that it has some virtues that I have so far failed to grasp, but I remain sceptical. ”
Ian Jolliffe
So you have it from the acknowledged foremost authority on PCA that Mann’s hocky stick was based on dubious statistics.
Troll,
Yes… I am a “despicable cunt”, for what exactly, no one knows but you. Whatever.
Again, you put words into my mouth. Apparently that’s the only way you know how to argue. (Other than to spout obscenities) Make up a false position for your “opponent”, claim they said it, and then knock it down.
I never said that the carbon cycle varies cyclically. I said that is a “cycle” that influences global climate. Although, I’d be willing to bet that if you were to actually check… there are aspects of the “Carbon Cycle” that do vary cyclically.
You are doing an extremely poor job of picking my posts apart. You have skipped over 90% of the things I’ve said, and then focused on one or two specific aspects and then MADE UP my position for me. Then you proceed to make a vulgar pronouncement that I’m wrong, followed by more name-calling.
In this whole amateurish process you provide no real information, no citable references, no *proof* of any kind that backs you up in any way. Honestly, you’re an ignorant, vulgar, sad-sack wannabe of marginal entertainment value and even less societal value. I’m surprised that Warren hasn’t banned you.
This discussion is over.
Doc
Waldoitshotouthere:
The most significant part of your whole quote can be found at the bottom of the page.
“Update… Thus, my contention that solar doesn’t explain much of the variability in this record isn’t valid.”
He just shut himself down.
Doc
Waldoitshotouthere:
Incredible !
You didn’t even read what you posted. Simply incredible.
Doc nailed your hide to the shed Fred !
Ummmm…read the entire post again carefully, netdr and Doc.
1) The whole point of the RC post is that we do not know about solar cycles to determine how much effect they have (did either of you actually read the post?).
2) The point of my post was to give Doc and hunter an actual expert on the subject. But most importantly in regard to your above comments…
Ready?
3) Gavin is talking only about one particular study as an example of a claim which overstates its conclusions. He is not talking about his entire post, simply a single study that he commented upon in the body of his post. You did see that, didn’t you? No? Oh, well here, let me help you.
This is para. #8
“Some contrarian commentators have recently fallen into the habit of mass mailing any new solar-related abstracts and implying that the existence of solar forcing in the past negates any possible recent anthropogenic impact on climate.”
In other words, some people are just too ready to declare solar activity the fabled forcing. Gavin says whoa nelly!
“Since these studies do not have any implication for the radiative impact of CO2, and don’t change the fact that there has been no effective change in any solar indices since about 1950, it is hard to see a substantial basis for this (implied) argument.”
Since these studies no not change the nature of CO2, and since there has been no change in solar activity since 1950, it is hard to see that there is a correlation between solar forcings and climate change.
Now here is where Gavin starts talking about the study he will later correct himself on:
“For instance, there has been a lot of recent attention paid to Mangini et al. (2005) where a solar link to a new Alpine speleothem record was claimed. However, a quick analysis (right) indicates that the explained variance in the record (smoothed over 25 years) correlated to the 14C-production function (a slightly cleaner solar proxy than the resdiual atmospheric 14C (Muscheler et al, 2005 – see comment/link below)) is only about 5%. Hardly a definitive refutation of anthropogenic greenhouse gas forcing.”
That’s it. In other words, there is nothing in Mangini et al to suggest that the study of solar forcings refutes any findings about CO2. Gavin estimates that the “production function” is only 5%. This is the only thing he is corrects – this 5% number, that’s it.
Later, because he is an honest commentator (unlike some people we know), Gavin comes back to point out that he made a mistake when talking about the variability of this particular study and writes “my contention that solar doesn’t explain much of the variability in this record isn’t valid. It could explain anything from 5 to 40% (with unknown error bars).” So his original point – that we don’t know enough yet about solar forcings – is still absolutely intact, with a de facto example to boot.
It’s pretty sad, folks, when a guy with my level of scientific training has to point something like this out. You should just begin each of your posts with “Oh yeah, well” before you begin posting about “climate mafias” and the like.
Sorry, netdr, no hides on the shed yet, my friend. Are you sure you’re actually an engineer? Why does your moniker link back to CS – a question you continually ignore.
Ah, so clearly you have forgotten why you even became obsessed with cycles. I suppose I’ll have to remind you:
“The cooling portion of a climate cycle that included the LIA ended roughly around 1800, give or take a few years. Now, what happens at the end of a cycle swing? Obviously, it goes back the other direction. Therefor, calling the warming that occurred NATURALLY after the LIA a “recovery” is just fine”
Obviously you think you know of all the supposed cycles you need to add together to understand the climate system perfectly, and you think they all add up to warming after 1800. So go on then, list all the cycles, their periods and their amplitudes. Show that they all add up to global warming. And explain why CO2 is not a greenhouse gas in your understanding.
Alternatively, admit that you said something spectacularly stupid, based on appalling ignorance and grotesque misunderstandings. And then stop bullshitting about subjects you know nothing of.
“I’m surprised that Warren hasn’t banned you”
Ha ha! You think he reads these comments? Have you ever seen even a single response to anything that anyone has said? He’s considerably more stupid even than you, and doesn’t have the intellect to understand the comments, let alone respond.
Waldo
Sorry it won’t wash.
“Update (Jul 24):Thus, my contention that solar doesn’t explain much of the variability in this record isn’t valid. It could explain anything from 5 to 40% (with unknown error bars). Sorry for any confusion.”
****************************************************************
The solar cycles could explain up to 40 % of the warming.
Your hide remains firmly nailed to the shed Fred !
Okay, now you’re just being stubborn – “could explain” – as in, ‘we don’t yet know’ the variability of “this (particular) record.” Which was the whole point of Gavin’s post in the first place and the whole point of his correction in the second. But that’s fine if you want to run around with your V-sign in the air, netdr, if it makes you feel better.
What I find fascinating is the mentality of the denialist camp. It’s obvious that netdr did not read or digest the post, and yet Mr. M…I mean, netdr’s first reaction is to begin looking for propagandistic statements such as “that is exactly what the CO2 mafia does.” Actually, this is exactly what someone like Limbaugh or Hannity does. Again netdr, you should just begin each post with “Oh yeah, well” and then continue from there. And then there’s Doc Navy who ostensibly has some scientific background who also apparently did not digest the content of the post and who immediately leaps on the idea that Gavin “shut himself down.”
As I’ve posted to Wally any number of times, there is no real science here, simply the adolescent need to declare victory over the bad guys. And this evaporates once we actually look at the what the bad guy scientists say rather than read some highly inflammatory cross-posting from C3 or some other blog-source.
Oh folks, how can you ignore this when it is so obvious?
In response to Waldy’s defense of Mann’s hocky stick:
To summarize, Mann created the “hockey stick” using non-centered Principal Component Analysis. McIntyre and McKittrick, and later Wegman, stated
that Mann’s use of non-centered Principal component Analysis was flawed, and that the algorithm in effect was “searching for hockey sticks”.
Mann et al at “realclimate”, on January 6, 2005, stated that McIntyre and McKittrick were mistaken, and cited “Jolliffe” as an authority on PCA, stating that
non-centered PCA was a valid procedure.
Tamino later posted a series on “PCA” on his blog, “Open Mind”. Part 4 was posted on March 6, 2008. In this posting he asserted that
non centerd PCA was perfectly okay, stating,
” You shouldn’t just take my word for it, but you should take the word of Ian Jolliffe, one of the world’s foremost experts on PCA…”
Finally there’s a reply from Ian Jolliffe himself, who in effect said McIntyre and McKittrick’s criticism was correct, and Mann’s hockey stick
was based on dubious statistics.
From the January 6, 2005 “realclimate” post,
http://www.realclimate.org/index.php/archives/2005/01/on-yet-another-false-claim-by-mcintyre-and-mckitrick/
“6 Jan 2005
On Yet Another False Claim by McIntyre and McKitrick”…
“McIntyre and McKitrick (MM), in one of their many false claims regarding the Mann et al (MBH98) temperature reconstruction, assert that the “Hockey Stick” shape of the reconstruction is an artifact of the “non-centered” Principal Components Analysis (PCA) convention used by MBH98 in representing the North American International Tree Ring Data Bank (ITRDB) data series. “…
“Contrary to MM’s assertions, the use of non-centered PCA is well-established in the statistical literature, and in some cases is shown to give superior results to standard, centered PCA. See for example page 3 (middle paragraph) of this review. For specific applications of non-centered PCA to climate data, consider this presentation provided by statistical climatologist Ian Jolliffe who specializes in applications of PCA in the atmospheric sciences, having written a widely used text book on PCA. In his presentation, Jollife explains that non-centered PCA is appropriate when the reference means are chosen to have some a priori meaningful interpretation for the problem at hand.” ….
On March 6, 2008, “Open Mind” defended Mann’s hockey stick.
http://tamino.wordpress.com/2008/03/06/pca-part-4-non-centered-hockey-sticks/
“First let’s dispense with the last claim, that non-centered PCA isn’t right. This point was hammered by Wegman, who was recently quoted in reader comments thus:
“The controversy of Mann’s methods lies in that the proxies are centered on the mean of the period 1902-1995, rather than on the whole time period. This mean is, thus, actually decentered low, which will cause it to exhibit a larger variance, giving it preference for being selected as the first principal component. The net effect of this decentering using the proxy data in MBH and MBH99 is to produce a “hockey stick” shape. Centering the mean is a critical factor in using the principal component methodology properly. It is not clear that Mann and associates realized the error in their methodology at the time of publication.”
Just plain wrong. Centering is the usual custom, but other choices are still valid; we can perfectly well define PCs based on variation from any “origin” rather than from the average. It fact it has distinct advantages IF the origin has particular relevance to the issue at hand. You shouldn’t just take my word for it, but you *should* take the word of Ian Jolliffe, one of the world’s foremost experts on PCA, author of a seminal book on the subject. He takes an interesting look at the centering issue in this presentation.”
And finally we get a reply from Jolliffe himself:
http://tamino.wordpress.com/2008/08/10/open-thread-5-2/#comment-21873
“Ian Jolliffe // September 8, 2008 at 9:36 am
Apologies if this is not the correct place to make these comments. I am a complete newcomer to this largely anonymous mode of communication. I’d be grateful if my comments could be displayed wherever it is appropriate for them to appear.
It has recently come to my notice that on the following website, related to this one, my views have been misrepresented, and I would therefore like to correct any wrong impression that has been given.
http://tamino.wordpress.com/2008/03/06/pca-part-4-non-centered-hockey-sticks/
An apology from the person who wrote the page would be nice.
In reacting to Wegman’s criticism of ‘decentred’ PCA, the author says that Wegman is ‘just plain wrong’ and goes on to say ‘You shouldn’t just take my word for it, but you *should* take the word of Ian Jolliffe, one of the world’s foremost experts on PCA, author of a seminal book on the subject. He takes an interesting look at the centering issue in this presentation.’ It is flattering to be recognised as a world expert, and I’d like to think that the final sentence is true, though only ‘toy’ examples were given. However there is a strong implication that I have endorsed ‘decentred PCA’. This is ‘just plain wrong’.
The link to the presentation fails, as I changed my affiliation 18 months ago, and the website where the talk lived was closed down. The talk, although no longer very recent – it was given at 9IMSC in 2004 – is still accessible as talk 6 at http://www.secamlocal.ex.ac.uk/people/staff/itj201/RecentTalks.html
It certainly does not endorse decentred PCA. Indeed I had not understood what MBH had done until a few months ago. Furthermore, the talk is distinctly cool about anything other than the usual column-centred version of PCA. It gives situations where uncentred or doubly-centred versions might conceivably be of use, but especially for uncentred analyses, these are fairly restricted special cases. It is said that for all these different centrings ‘it’s less clear what we are optimising and how to interpret the results’.
I can’t claim to have read more than a tiny fraction of the vast amount written on the controversy surrounding decentred PCA (life is too short), but from what I’ve seen, this quote is entirely appropriate for that technique. There are an awful lot of red herrings, and a fair amount of bluster, out there in the discussion I’ve seen, but my main concern is that I don’t know how to interpret the results when such a strange centring is used? Does anyone? What are you optimising? A peculiar mixture of means and variances? An argument I’ve seen is that the standard PCA and decentred PCA are simply different ways of describing/decomposing the data, so decentring is OK. But equally, if both are OK, why be perverse and choose the technique whose results are hard to interpret? Of course, given that the data appear to be non-stationary, it’s arguable whether you should be using any type of PCA.
I am by no means a climate change denier. My strong impressive is that the evidence rests on much much more than the hockey stick. It therefore seems crazy that the MBH hockey stick has been given such prominence and that a group of influential climate scientists have doggedly defended a piece of dubious statistics. Misrepresenting the views of an independent scientist does little for their case either. It gives ammunition to those who wish to discredit climate change research more generally. It is possible that there are good reasons for decentred PCA to be the technique of choice for some types of analyses and that it has some virtues that I have so far failed to grasp, but I remain sceptical. ”
Ian Jolliffe
So straght from the horse’s mouth, Mann’s use of non centered PCA was crap-
**************************
To summarize, Mann created the “hockey stick” using non-centered Principal Component Analysis. McIntyre and McKittrick, and later Wegman, stated
that Mann’s use of non-centered Principal component Analysis was flawed, and that the algorithm in effect was “searching for hockey sticks”.
Mann et al at “realclimate”, on January 6, 2005, stated that McIntyre and McKittrick were mistaken, and cited “Jolliffe” as an authority on PCA, stating that
non-centered PCA was a valid procedure.
Tamino later posted a series on “PCA” on his blog, “Open Mind”. Part 4 was posted on March 6, 2008. In this posting he asserted that
non centerd PCA was perfectly okay, stating,
” You shouldn’t just take my word for it, but you should take the word of Ian Jolliffe, one of the world’s foremost experts on PCA…”
Finally there’s a reply from Ian Jolliffe himself, who in effect said McIntyre and McKittrick’s criticism was correct, and Mann’s hockey stick
was based on dubious statistics.
From the January 6, 2005 “realclimate” post,
http://www.realclimate.org/index.php/archives/2005/01/on-yet-another-false-claim-by-mcintyre-and-mckitrick/
“6 Jan 2005
On Yet Another False Claim by McIntyre and McKitrick”…
“McIntyre and McKitrick (MM), in one of their many false claims regarding the Mann et al (MBH98) temperature reconstruction, assert that the “Hockey Stick” shape of the reconstruction is an artifact of the “non-centered” Principal Components Analysis (PCA) convention used by MBH98 in representing the North American International Tree Ring Data Bank (ITRDB) data series. “…
“Contrary to MM’s assertions, the use of non-centered PCA is well-established in the statistical literature, and in some cases is shown to give superior results to standard, centered PCA. See for example page 3 (middle paragraph) of this review. For specific applications of non-centered PCA to climate data, consider this presentation provided by statistical climatologist Ian Jolliffe who specializes in applications of PCA in the atmospheric sciences, having written a widely used text book on PCA. In his presentation, Jollife explains that non-centered PCA is appropriate when the reference means are chosen to have some a priori meaningful interpretation for the problem at hand.” ….
On March 6, 2008, “Open Mind” defended Mann’s hockey stick.
http://tamino.wordpress.com/2008/03/06/pca-part-4-non-centered-hockey-sticks/
“First let’s dispense with the last claim, that non-centered PCA isn’t right. This point was hammered by Wegman, who was recently quoted in reader comments thus:
“The controversy of Mann’s methods lies in that the proxies are centered on the mean of the period 1902-1995, rather than on the whole time period. This mean is, thus, actually decentered low, which will cause it to exhibit a larger variance, giving it preference for being selected as the first principal component. The net effect of this decentering using the proxy data in MBH and MBH99 is to produce a “hockey stick” shape. Centering the mean is a critical factor in using the principal component methodology properly. It is not clear that Mann and associates realized the error in their methodology at the time of publication.”
Just plain wrong. Centering is the usual custom, but other choices are still valid; we can perfectly well define PCs based on variation from any “origin” rather than from the average. It fact it has distinct advantages IF the origin has particular relevance to the issue at hand. You shouldn’t just take my word for it, but you *should* take the word of Ian Jolliffe, one of the world’s foremost experts on PCA, author of a seminal book on the subject. He takes an interesting look at the centering issue in this presentation.”
And finally we get a reply from Jolliffe himself:
http://tamino.wordpress.com/2008/08/10/open-thread-5-2/#comment-21873
“Ian Jolliffe // September 8, 2008 at 9:36 am
Apologies if this is not the correct place to make these comments. I am a complete newcomer to this largely anonymous mode of communication. I’d be grateful if my comments could be displayed wherever it is appropriate for them to appear.
It has recently come to my notice that on the following website, related to this one, my views have been misrepresented, and I would therefore like to correct any wrong impression that has been given.
http://tamino.wordpress.com/2008/03/06/pca-part-4-non-centered-hockey-sticks/
An apology from the person who wrote the page would be nice.
In reacting to Wegman’s criticism of ‘decentred’ PCA, the author says that Wegman is ‘just plain wrong’ and goes on to say ‘You shouldn’t just take my word for it, but you *should* take the word of Ian Jolliffe, one of the world’s foremost experts on PCA, author of a seminal book on the subject. He takes an interesting look at the centering issue in this presentation.’ It is flattering to be recognised as a world expert, and I’d like to think that the final sentence is true, though only ‘toy’ examples were given. However there is a strong implication that I have endorsed ‘decentred PCA’. This is ‘just plain wrong’.
The link to the presentation fails, as I changed my affiliation 18 months ago, and the website where the talk lived was closed down. The talk, although no longer very recent – it was given at 9IMSC in 2004 – is still accessible as talk 6 at http://www.secamlocal.ex.ac.uk/people/staff/itj201/RecentTalks.html
It certainly does not endorse decentred PCA. Indeed I had not understood what MBH had done until a few months ago. Furthermore, the talk is distinctly cool about anything other than the usual column-centred version of PCA. It gives situations where uncentred or doubly-centred versions might conceivably be of use, but especially for uncentred analyses, these are fairly restricted special cases. It is said that for all these different centrings ‘it’s less clear what we are optimising and how to interpret the results’.
I can’t claim to have read more than a tiny fraction of the vast amount written on the controversy surrounding decentred PCA (life is too short), but from what I’ve seen, this quote is entirely appropriate for that technique. There are an awful lot of red herrings, and a fair amount of bluster, out there in the discussion I’ve seen, but my main concern is that I don’t know how to interpret the results when such a strange centring is used? Does anyone? What are you optimising? A peculiar mixture of means and variances? An argument I’ve seen is that the standard PCA and decentred PCA are simply different ways of describing/decomposing the data, so decentring is OK. But equally, if both are OK, why be perverse and choose the technique whose results are hard to interpret? Of course, given that the data appear to be non-stationary, it’s arguable whether you should be using any type of PCA.
I am by no means a climate change denier. My strong impressive is that the evidence rests on much much more than the hockey stick. It therefore seems crazy that the MBH hockey stick has been given such prominence and that a group of influential climate scientists have doggedly defended a piece of dubious statistics. Misrepresenting the views of an independent scientist does little for their case either. It gives ammunition to those who wish to discredit climate change research more generally. It is possible that there are good reasons for decentred PCA to be the technique of choice for some types of analyses and that it has some virtues that I have so far failed to grasp, but I remain sceptical. ”
Ian Jolliffe
**************************
@Waldoitshotouthere
Firstly, great to see a reasoned post which appears on face value to be from a real scientist.
I am leaning somewhat toward the skeptic side of this debate not because I am a scientist (I am an engineer), nor becasue I have read much of the literature, but because on face value the AGW predictions have failed, and far from “its hot out here”, if sea temperature is anything to go by then it is perhaps just slightly cooler.
Walsoroooo bemoans the lack of science in here (perhaps rightly), but the intention of this blog is not to be a discussion between “scientists”, but a forum for discussion between interested people. It is fair for him to pleade with the bloggers about what is obvious, but what seems increasingly obvious to me, and so far, all other engineers I meet, is that the King has got fewer and fewer clothes on every week. I think the bored shepherd boy has cried wolf twice already too.
A scientific theory which is all about prediction clearly needs to be able to predict to some degree, and not just make excuses for why it keeps failing. Netdr quite rightly uses the “racing forms” analogy. If it is invalid then it should be pretty easy for a real scientist to outline the predictions that have been validated, and for these to then be open for discussion.
Waldo,
“The whole point of the RC post is that we do not know about solar cycles to determine how much effect they have (did either of you actually read the post?).”
For fuck sake Waldo, did YOU read that paper you picked in the other thread? A very large part of it was dealing with how the forcings we know of, LIKE SOLAR CYCLES, effect the Earth’s temperature. How about you go back and read a PEER REVIEWED journal (you know the things you give so much more credibility than a stupid blog like realclimate), and try to actually learn something this time. If that paper doesn’t explain certain topics well enough for you, look up the citations used in the sections where you get confused (ok, you might as well pull the entire reference listing), then see if you can learn something again. If you can’t repeat until you do, or until you admit it to yourself that you will never understand.