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Astronomical cycles

Posted on 17 June 2010 by Riccardo

Guest post by Riccardo

Recently a new paper by Scafetta came out (a freely downloadable version can be found on arxiv but I don't know if they are exactly the same). In a few words, Scafetta connect the orbital motion of the planets with solar variability and hence on earth climate. He found a dominant 60 years cycle which, he claims, greatly downplay the anthropogenic contribution to the warming after the '70s. I won't go through the details of his analysis and the hypothesis on the yet to be discovered physical mechanism behind. Forget about physics for a moment, as Scafetta does, and think only about cycles and periods.

He does a nice and fascinating analysis of various orbital cycles which cause the motion of the sun around the center of mass of the solar system. It's assumed that in one way or another the gravitational pull affect sun activity. He then compares the power spectra from detrended Hadley's temperature data with that of the orbital cycles and obtains the nice graph reproduced below.


Fig.1: reproduction of fig. 10B in the original paper. It shows the eight years moving average of the temperature anomaly detrended of its quadratic fit (gray); the thin black line is the same curve shifted by 61.5 years.

The data has been detrended assuming an underlying parabolic trend. The main 60 year cycle, due to the alignment of Jupiter and Saturn, shows up very clear, but there are more. In particular, he identifies a total of 10 cycles due to combination of planets motion and one due to the moon (fig. 6B in the paper). Of those cycles, only two more are considered significant, namely those with periods of 20 and 30 years.

Fascinating. But then, a few pages later, Scafetta writes:

However, the meaning of the quadratic fit forecast should not be mistaken: indeed, alternative fitting functions can be adopted, they would equally well fit the data from 1850 to 2009 but may diverge during the 21st century.

His warning is on the problem of extrapolation of the trend in the future, which he nonetheless shows. But this sentence made me think that it's true, once we put physics aside, we're free to use the trend we like; so why parabolic?  I decided to take a closer look, and this turns out to be the begining of the end.

The first and more obvious try is a linear trend and then one with a higher power. I kept the functional form y=a(x-1850)n-b used by Scafetta, but let n be 1,2 or 4. Here's what I got.


Fig.2: HadCRUT3 monthly data (grey) and the fits for n=1 (red), 2 (green) and 4 (blue).

Already by eye inspection it may be noticed that, due to the different curvature of the fitting functions, the behaviour is different between the middle and the extremes of the range. To be quantitative, we need to calculate the residuals, i.e. the difference between the data and the trends.

The fits were performed using the raw monthly data, as shown in fig. 2, but given that we are looking for long term cycles, I smoothed the data before detrending to clean them up a bit, as Scafetta did too. The results are shown in the following figure.


Fig.3: residuals calculated with the trend curve shown with n=1 (red), 2 (green) and 4 (blue).

As noted before, the behaviour at the extremes of the range is opposite with respect to that at the center and the two peaks at year 1880 and 2000 get smaller on increasing n. In particular, for n=1 the curve barely flattens aroud year 2000 while for n=4 only a small short-lasting peak is left. Only with n=2 we get the three nice equal amplitude peaks.

More generally, for n=4 the claimed 60 year cycle seems to vanish after the peak at year 1940. It's not to say that the n=4 trend has more value than the n=2, but in the end we can say that the nice cyclic behaviour seen in fig. 1 depends on the choice of the trend function. It's worth to recall that its choice is arbitrary, no physics behind it.

I tested this findings with the other global surface temperature datasets (GISS and NCDC) and, not unexpectedly, they confirmed. The claim that the anthropogenic contribution to the increase in temperature after the 70s has been overestimated has then to be dismissed, at least until we can make a proper choice of the underlying trend.

Still, small, periodic and short-lasting peaks seem to be real. More accurate and hopefully physics-based studies on decadal variability are required, taking into account all possible internal and external contributions.

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Comments 1 to 50 out of 141:

  1. Good work Riccardo. There is a fallacy in archaeology which goes like this. I find a piece of stone in the ground and I don't know what it is. So I juggle it around in my hands a bit and hey presto, if it sits a certain way my hand will fit around this knob here, so it must be a tool. The problem is that almost any piece of stone (or wood) can be held in a certain way and therefore be a tool. This fallacy is particular active in the study of early human society with (often) very simple technology, and there have been many instances of "early human" tool use being postulated which have later evaporated.

    In fact there are objective ways you can decide if something is a stone tool, based on such things as type of stone, fracture pattern, secondary chipping, use wear, residue analysis, and a comparison between an individual item and others at the same site, or of the same age, and so on. Some you may be able to hold in your hand, most not, for many there can be endless debate about exactly how they were used. But all of this has to be based on objective research, not after the fact hypotheses.

    In short, you can't just look at some mathematically created cycle and then invent a reason for it and then use it to predict the future. The graph may seem to fit well in the hand, but this is almost always an illusion based on wishful thinking.
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  2. I will defer to smarter folks that are surely going to comment after me here, but I think it would be problematic to dismiss anthropogenic CO2's role in current climate change based on one paper, as you suggest. From everything that I've read there is a great deal of paleoclimate that gets explained very neatly by atmospheric CO2 and rock weathering cycles. If you dismiss the role of CO2 in temperature then you have to explain how these mechanisms also work in a very long list of other areas.
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  3. Hats off to Riccardo for doing this.

    Leaving aside for moment the confusion this paper will undoubtedly sow, from my mile wide, inch deep perspective I found Scafetta's paper to be enjoyable because he's not at all inhibited about throwing open his kitchen shelves and dumping in whatever ingredients might spice up the dish at hand. In this case I learned that the traditional Chinese calendar includes a 60 year cycle, of dubious relevance to the topic but nonetheless interesting to learn. Scafetta enthusiastically throws himself into the sauce: Perhaps, this sexagenary cyclical calendar was inspired by climatic and astronomical observations. There's also a ton of other intriguing arcana on orbital phenomena.

    Unfortunately Scafetta goes on to claim that current models are "fundamentally" flawed because they fail to incorporate his unidentified physical mechanism and as well predicts a cooling world in the decades to come, these conclusions being the strained-metaphor equivalent of smoke belching out of the oven as Scafetta's dish is overcooked.
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  4. Interesting. Can't you use likelihood to choose between models. That would be a little less than arbitrary. Of course, the choice will be heavily influence by what happens at the ends of the series, and I guess Scaffeta would then argue that the offsets at the extremes are real because they match his expectation. So maybe it gets you nowhere in the end. It's still arbitrary.

    Is there any way physically to link gravity variations driven by orbital cycles to variations in solar output? I'm not up on this.
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  5. Fitting 2.5 "cycles" with some arbitrary post-hoc function: isn't this a lovely example of the sort of spam that peer review is supposed to catch?
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  6. Not such a stupid proposition. Gravity affects the sun, the sun affects us. But the sun is still very quiet, and we are at record (globally averaged)Jan to May temperatures.

    Is there any data about the tilt of the sun compared to the planetary planes.

    If there is anything in Scafetta, it will probably end up showing we should be freezing right now.
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  7. Stephen "Is there any way physically to link gravity variations driven by orbital cycles to variations in solar output?" - I don't know either and while it seems very unlikely to me I guess anything is possible.

    But there is the more general point that I think arises from this (and many other denier hypotheses) and that is that you can't do this stuff post hoc. Let us imagine that some cosmologist had done a careful analysis of the orbital variations of the planets and that the changes in gravity effects contributed by these (especially Jupiter and Saturn) could be calculated and those effects in turn could be shown by some well known physical/chemical mechanism to affect the output of heat from the Sun. You could then turn around and say "oh, I wonder if that changing output has affected the temperature on Earth". You would then do the calculations of the amount of heat variation, the pattern of global warming, and connect the two in a graph and show that this then also matched the orbital variations of the planets.

    If you do the reverse, the search for some apparent patterns in the past which just happen to match something else, then you are looking at correlation not causation. Ironic, is it not?
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  8. This doesn't look fundamentally different from the curve-fitting "it's mostly PDO" argument. Ignore physics entirely and try to find a correlation somewhere (this time with a more obscure unexplained physical mechanism), using a variety of selected data.

    It reminds me of a friend of mine who asked me about a Superbowl prediction system that claimed to be 90% successful. It had all sorts of obscure metrics such as "number of 4-point victories this season" and "number of extra points blocked". When about 20 metrics were combined, it accurately predicted winners of about 90% of past Superbowls. I advised him that given the sheer number of data metrics to choose from, one will always be able to combine any obscure metrics together for an accurate hindcast. There's no rhyme or reason to it, and such a system is likely to be no better than 50/50 going forward. Well...it's been 3 years and it correctly predicted 2 out of 3 Superbowls. So my friend thinks it's been vindicated. (Sigh...)

    Anyone can find a correlation.

    http://www.skepticalscience.com/The-CO2-Temperature-correlation-over-the-20th-Century.html

    If the CO2 / global temperature link was based simply on a correlation, it would be rightfully attacked.

    I suspect "skeptics" won't meet Scafetta's study with appropriate skepticism. That's what this site is for.
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  9. We're human - and we're really really good at seeing patterns. There are tons of papers in this; seeing patterns in woodland undercover (nasty critters!), environmental noise (there's somebody behind me!), and even in tea leaves (I have no idea here, I never see anything but leftover tea!).

    In unmitigated nature this is a huge advantage. The cost of a false positive is a short period of panting and high blood pressure, while the cost of a false negative is much higher - being eaten by something, or clubbed by a competing caveman. However, as a result of a false positive pattern bias, we also see gnomes in Zurich manipulating currency, UFO's in clouds, conspiracies among the neighborhood pets, on and on and on.

    If you go looking for a pattern, you're likely to find one somewhere. I'm much more impressed (charitable?) when someone finds that a pattern falls out of their data, and then search for and find a corresponding pattern in a reasonably forcing influence.
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  10. Ok, folks. Global warming theory has been debunked once and for all. I've found a strong correlation between S&P 500 stock index growth and global mean temperature (NCDC) since 1950, using a linear trend with the proper scaling and a 36 month running average.



    As is obvious, there's very little room left for greenhouse gases.

    Ok maybe not the perfect analogy to Scafetta, but you get the idea.
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  11. Warming is good for the economy!
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  12. Bravo NewYorkJ!

    I am now adjusting my position in the market based on correlations with temp projections (or NOT!). Thanks.

    On the one hand, correlations point to possible connections, so it is valuable to explore them. On the other hand... explain the cause to me before I endorse a correlation as a cause.

    I viewed the paper at arxiv. The most striking thing to me is that the author superimposes a periodic temperature variation upon a QUADRATICALLY growing base, and doesn't address (did I miss it) why the base temp at any moment is accelerating in time. Argh! His correlations may "explain" some periodic variability, but only if the base temp is accelerating over time. Good grief! Is the author offering an "astrological" explanation of why the temp of the earth is accelerating, or not? I didn't catch it if the author did. The acceleration is the "trend" that concerns me.

    Is the author suggesting the quadratic base curve is statistically significant? If not, the whole analysis is suspect. If it is, then the problem is to explain it. I offer a wacky idea... something to involving CO2 emissions.
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  13. Donald Lewis - well, yeah, that's the thought I had. The author "detrends" the data, and then goes to great lengths to show there may be a cyclical influence on the Earth's climate by the orbits of the gas giants. Ignoring the issues of choice of underlying trend that Riccardo has pointed out, it might explain some of the ups'n'downs over the years, but the fact that he gets such a neat correlation surely means that it *cannot* explain the underlying trend.

    I.e. doesn't this paper, when accepted at face value, 'prove' that orbital variations cannot be causing global warming?
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  14. Lies, damn lies and...
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  15. Apparently this is a pattern with Scafetta.

    http://www.physorg.com/news189845962.html

    "The first thing we do when we approach a time series with a strong random component is to perform standard statistical analyses like plotting of probability density distributions on different time scales,” Martin Rypdal told PhysOrg.com. “We look at the shape of these rescaled distributions. If the signal is statistically self-similar, it looks almost the same on all time scales. [Here, we’ve shown] that the solar flare signal and the global temperature signal are both self-similar, but their distributions are very different, and so are the exponents used for rescaling. We were very surprised that Scafetta and- West never show such results in their papers. It seems that they have designed all their tests with the purpose of proving a wanted result, and deliberately avoided analysis that points in other directions."

    "The theory of anthropogenic global warming consists of a set of logically interconnected and consistent hypotheses,” Martin Rypdal said. “This means that if a cornerstone hypothesis is proven to be false, the entire theory fails. A corresponding theory of global warming of solar origin does not exist. What does exist is a set of disconnected, mutually inconsistent, ad hoc hypotheses. If one of these is proven to be false, the typical proponent of solar warming will pull another ad hoc hypothesis out of the hat. This has been the strategy of Scafetta and West over the years, and we have no illusion that our paper will put them to silence. "
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  16. Note the facts:
    1st Maximum solar activity in recent times (1957-1958 - XIX solar cycle) very closely coincide with the maximum: "mass moments of the 4 largest planets" (The cyclic fluctuations of air temperature in Europe in the 19th-21st centuries and their causes, Boryczka, Stopa-Boryczka, 2007). Perhaps this is the impact of increased "gravitational activity," the Sun?
    Okay, Marcus says: that in 30 years solar activity is falling ..., but our recent discussion about the MWP shows that (asynchrony: NH - SH), Earth's climate system can respond to changes are with considerable delay.
    3rd The cycle average of 60 years in long periods of time Millennium fits perfectly such as AMO, CTH ..., but also in a cycles of Millennium. In the latter - only the LNC. (Ledu, Rochon de Vernal, Labrie, 2007. Holocene climate oscillations in the Eastern part of the Northwest Passage: A possible influence of the Lunar nodal cycle: Preliminary results.). The importance of lunar cycles is undeniable. I recommend:
    - Lunar nodal tide effects on variability of sea level, temperature, and salinity in the Faroe-Shetland Channel and the Barents Sea (Yndestad at al., 2008);
    - The 18.6-year lunar nodal cycle and surface temperature variability in the northeast Pacific (McKinnell , and Crawford; 2007 ),
    - The impacts of the Luni-Solar oscillation on the Arctic oscillation (Ramos da Silva and Avissar; 2005),
    - Trends and anomalies in sea-surface temperature, observed over the last 60 years, within the southeastern Bay of Biscay (Goikoetxea, 2009),
    - Solar Forcing of Changes in Atmospheric Circulation, Earth's Rotation Solar (Mazzarella, 2008).

    2. Effect of LNO-LNC on the extent of THC is proven, to be only measured how big the impact is and how "to translate" the retention of solar energy by the global climate system.
    I hope that someone will do it, I do not have the appropriate team of "human" and financial resources.

    4. And (once again) I recall a diagram: http://www.rni.helsinki.fi/research/info/sizer/fig2big.jpg (unfortunately, my computer software is not able to paste this chart - here - and we would show it off.)
    The climate of Fennoscandia is a "terminal" for at least two climate circulations, also applies to the polar latitudes; and is therefore highly sensitive climate change. The main noticeable change in the climate of Fennoscandia may thus be important also for the Earth ... In the diagram Finnish scientists, it is clear that we are now at the stage of warming (after rapid cooling) - in a very similar period to circa 4.2 and 8.4 thousand years ago ... There are multiple Millennium cycles. This "same" Rahmstorf says that: "the Millennium cycle is dependent on the cycles of the sun [60 lat ?] - but not directly. So far, created a few theories to explain this relationship." Rahmstorf, Ganopolski, 2005: "We attribute the robust 1,470-year response time to the superposition of the two shorter cycles, together with strongly NONLINEAR DYNAMICS and the long characteristic timescale of the thermohaline circulation."

    PS Sorry for the big shortcuts (for: gravity Sun) - I hope that this is not from my lack of knowledge, but the lack of "place" on a precise explanation.
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  17. sorry "[60 lat]" - 60 years
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  18. Arkadiusz Semczyszak,
    the problem at hand is the validity of Scafetta approach. What I tried to show is that it's weak, at best.
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  19. In part, I feel guilty about working Scafetta. In a discussion of his earlier work: Is climate sensitive to solar variability? (2008), pointed out that it may be important not only: "Modeling the TSI variability Earth's atmosphere, landmasses, and oceans absorb and redistribute the total solar irradiance (TSI) ..." The discussion (also) was attended by Richard Mackey ...

    Agreed. Scafetta papers much simplifies the problem and is "fraught" with considerable range of possible deviations. But I hope that the problem resulting from the fact that: "Schwabe and Hale solar cycles are also visible in the temperature records. A 9.1-year cycle is synchronized to the Moon's orbital cycles."; will be appreciated - clearly explained and "priced". Ricardo: problem can not be underestimated.
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  20. Arkadiusz, if planetary alignments were truly having such a strong impact on the sun, then we'd see some kind of outward sign-such as a large increase in solar activity-yet if anything the sun's activity is *declining*. Also, your talk about the supposedly asynchronous nature of the MWP is a complete red herring-because whatever the northern & southern hemispheres were doing during the MWP, we *know* that sunspots were increasing throughout that entire time-the same is *not* true at the moment.
    Also, the last time sunspot numbers peaked (the 60 years from 1890-to 1949) temperatures rose at a rate of +0.06 degrees per decade. By contrast, the warming of the last 60 years (1950-2009) has been at +0.11 degrees per decade-in *spite* of being dominated by a decline in solar activity.
    Still, at the end of the day, this article is more about Scaffetta's attempt to squeeze the trend to fit his hypothesis, on extremely flimsy pretexts, as Riccardo eludes to. Still, Arkadiusz, I've got to admire your talent for rejecting perfectly rational explanations of warming-even when based on strong empirical evidence-yet happily cling to the most outlandish explanations the Denialist Club can come up with!
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  21. Arkadiusz Semczyszak,
    you should have noticed that, although criticizing the analisys shown in the paper I ended the post open to other possibilities and welcoming further studies on decadal variability, which anyone may admit is a bit in its infancy. I can't see where you criticism of underestimation is based on.
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  22. Marcus at 21:18 PM, this chart perhaps helps with sunspot numbers.
    The relevant temperature trends are
    (a) A small temperature fall 1900 to 1906.
    (b) An extended temperature rise 1906 to 1940.
    (c) A steady or very slowly descending temperature period from 1940 to 1978.
    (d) An extended fairly rapid rise in temperatures from 1978 to 1998.
    (e) A short steady or slightly descending temperature period from 1998.

    http://www.ngdc.noaa.gov/stp/GEOMAG/image/aassn07.jpg
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  23. Johnd @22,

    I'm not sure what the point of your cursory analysis is. That sunspot number explains decadal trends in the global surface air temperature? Anyhow, I disagree with your assessment that (e).

    The OLS trend in the GISTEMP data between 1998 (~12 years) and now is +.134 K/decade, compared to +.09 K/decade between 1986 and 1998 (~12 years prior to 1998). Stats generated at woodfortrees.org.

    Why did you choose 1998?
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  24. Albatross at 02:38 AM, the trends are taken from the chart below. The question really is why did you choose 1986 when it appears the upward trend began about 1978?

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  25. johnd,
    from NCDC data the linear trend from 1998 is positive. Same conclusion eyeballing the blue line in your graph. Only if you take the value of the single year 1998 and the single year 2009 you'll get a slightly decreasing temperature. Is this what you mean?
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  26. JohnD,

    The question remains why you chose 1998-- a year frequently cited by "skeptics", some erroneously, as the warmest year to date in the instrumented record. The follies of "cherry-picking" start dates, has been discussed ad nauseum.

    The only reason I chose 1986-1998 is because you chose 1998-present (~12 years), so I selected the 12 years prior to 1998 so that we would at least be comparing trends determined using the same number of data points. To calculate stat sig. trends one needs at least 15 years or so of data in the GISTEMP data.

    The trend in GISTEMP from 1978 to 1998 (i.e., using the dates that you suggested @24) was +0.123 K/decade, compared to +0.134 K/decade from 1998 to present. The trend from 1978 to preset is +0.168 K/decade.

    So, the trend between 1998 and present is positive, and even greater than that observed between 1978 and 1998 (although the difference between the two is probably not statistically significant). Anyhow, your suggestion that global temperatures have been stable since 1998 or have even cooled since 1998 is simply not correct.

    Hansen et al. have a paper (which you can download from his web site) in which they demonstrate that the long term rate of warming in the GISTEMP until present has not showed signs of a (prolonged) slow down in the warming. It is a very interesting paper and well worth reading if you have the time (it is rather long).
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  27. Seriously JohnD, if you're going to come here & debate the issue, then at least try & make an effort! Dusting off tired old "skeptic" arguments & passing them off as new might work in the denialosphere-or even in the blogs of the Mainstream Press, but you'll need to do a bit more leg-work here!

    For the record, the usual convention in determining decadal trends is to use *actual decades* (say 1980-1989). If we do that, then we get the following warming trends: 1970-1979: +0.06 degrees/decade; 1980-1989: +0.055 degrees/decade; 1990-1999: +0.16 degrees/decade; 2000-2009: +0.13 degrees per decade.

    Now average sunspot trends for these decades were: +2/year; -5/year; -9/year & -14/year. So that *really* makes your argument look incredibly shaky JohnD! Time to go home & do your homework I reckon!
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  28. Philippe Chantreau at 16:22 PM on 17 June, 2010
    Lies, damn lies and... science. Scaffetta puts forward an analysis that is there to be questioned. That's not lying that's stepping into the unknown, that's science.

    Good post Riccardo, as usual it leaves me with more question than answers.

    I guess it is not controversial to state that the 20th century temperature record could be understood as cycles overlaid by a trend? Understanding the nature of those cycles seems important. Do you know any other theories out there regarding the cycles?

    How do other's try to separate out the natural cycles from the temperature trend? The fact that the IPCC says that almost all late 20th warming is due to GHGs suggests to me that they do not recognize that this period is part of the upward trend of one of these cycles? Is that true?

    Finally only last week I was trying to work out the amplitude of the natural cycle. Scafetta seems to put it at ~0.4oC. I was interested in this in connection to the supposed affects AGW would have of seasons, phenology, extinctions etc. It's interesting to consider that species naturally would have to cope with 0.4oc changes every 30 years if Scaffetta's analysis was true. Adaptibility within species (even over a short period) does not seem to be figured into the more doomsday scenarios.
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  29. HR - its all to easy to say "could be a natural cycle" which is somehow supposed to be a causeless phenomena too mysterious to penetrate. However, tomorrow's weather has physical causes; the ESNO has a physical cause etc. Where is this other mysterious cycle which somehow has rates of change so much higher than we are used to? Now it might exist - but the alternative hypothesis that the temperature record can be understood entirely on the basis of forcings plus some internal variability seems one how of a lot stronger and the best basis for a risk assessment. How much up trending would it take for you abandon the natural cycle hypothesis and what would it cost us by then?
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  30. "The fact that the IPCC says that almost all late 20th warming is due to GHGs"

    The IPCC is actually quite conservative and nuanced. Here's what they conclude:

    "Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic"

    "Most" meaning >50% and "very likely" meaning >90%.

    Interestingly, Scafetta makes a similar statement in his latest:

    "This estimate should be compared with the IPCC’s estimate that 100% of the warming observed since 1970 is anthropogenic."

    Perhaps there's a different statement in the IPCC report that you both are referring to, but this appears to be another reason to suspect a sloppy/poor review of this paper.
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  31. HR, if the last 60 years is all part of some natural cycle, then we should be able to detect identical trends during previous 60 year cycles. The reality is, though, that we can't. By Scafetta's analysis, the last 60 year cycle was 1890-1949, but I've already shown how-in spite of a large growth in average sunspot numbers-the rate of warming was only +0.06 degrees per decade. Compared to +0.11 degrees per decade for 1950-2009, in spite of a fall in sunspot numbers over this time period. That suggests to me that something other than natural cycles is at work!
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  32. scaddenp

    So what you're saying is that it is controversial that the 20th century is made up of 60years cycle with an underlying up trend? I can see it's a short time period to recognize a cycle and confused by other factors but I had it in my head that wasn't controversial. The HADCRUT3 data in fig2 seems to show rise/fall/rise/fall/rise (with an underlying up trend)

    NewYorkJ

    I was referring to the IPCC's statement on post 1970's data. If late 20th century is almost all AGW then there is no room for an upstroke on a natural cycle as suggested by figure 1.

    Marcus

    I did say natural cycle with an overlying trend and Scaffetta detrends the data for a reason. I think one of the questions raised by this is not if all the late 20th warming can be explained by natural cycles but whether we need to unpick the complex factors affecting the global temperature. At risk of repeating myself it seems the IPCC rule out any component of the 1970-2000 temperature trend being part of a natural cycle.
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  33. Humanity Rules @32,

    "At risk of repeating myself it seems the IPCC rule out any component of the 1970-2000 temperature trend being part of a natural cycle."

    Not true. From the IPCC, AR4:

    "Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic GHG concentrations.[7]"

    Also,

    "it is extremely unlikely that global climate change of the past 50 years can be explained without external forcing and very likely that it is not due to known natural causes alone. During this period, the sum of solar and volcanic forcings would likely have produced cooling,..."

    Also, read this

    There is more in the Copenhagen Diagnosis.

    Also consider this new paper
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  34. 'So what you're saying is that it is controversial that the 20th century is made up of 60years cycle with an underlying up trend? I can see it's a short time period to recognize a cycle'>

    Of course I its controversial. Its not controversial that trend is overlaid with ENSO quasi-periodic cycle. McLean et al kindly showed that you can explain much of the cycle that way. But a longer term cycle? Nope. The alternative explanation that it is response to forcing make more sense physically since no natural cycle in energy flow has so far been discovered.

    Perhaps also look at this Cyclical?
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  35. 33.Albatross

    I think I accepted that the IPCC says 1950 onwards is most, it's 1970's onward were they suggest almost all.

    So nature has a nett cooling affect for the past 50 years? So the IPCCC does seem to completely reject the presense of 60 years cycles with 1970-2000 being the up stroke of the cycle?

    It seems this article is suggesting that in playing a mathematical game Scaffetta is identifying a cycle, it should equally be stated that Riccardo is questioning this with his own little mathmatical game. I'm interested in the HADCRUT3 data in fig2. It overall trends up but with periods of rise/fall/rise/fall/rise. Is this not real? Does that need an explanation? This is surely an up trend with a cycle? if not what is the alternative explanation for the phases?

    Surely this is what AGW wants? An a clean uptrend that mirrors the uptrend in CO2 emmissions? Surely AGW wants to remove the mess of interferring factors (such as solar,volcanos and cycles) to leave a nice AGW trend?
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  36. Just so I am clear here - am I supposed to understand that regardless of the exponent of n, we would still be left with some version of the underlying SCMSS cycle that was found by Scafetta? If not, isn't this analysis a trifle incomplete? If Scafetta's detrending plus SCafetta's cycle match up pretty well with the observed temp records, then that is a decent reason to use it as a basis to predict future temps. However, detrending without an explanation of the causes of changes in the detrended data doesn't tell us much of anything.

    Cheers, :)
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  37. HumanityRules,
    I did not proposed a different mathematical game, I intentionally played the same game as Scafetta to show its inherent weakness using his own rules.
    As for the rise and fall, they're real and the widely accepted explanation is (roughly) that it's the sun plus volcanic activity (which no one want to disregard) with anthropogenic forcing dominating the final rise up to today. Disproving this explanation is what Scafetta was trying to do, unsuccessfully in my opinion.
    As for variability and apparent cycles, it's well assessed that a good part of the measured variability is due to ENSO, a cause of cyclic variability no one overlooks. Once it's effect is removed not much is left and no evident cycles can be spotted.

    shawnhet,
    if you assume the reality of the 60 years cycle and fit trend plus the cycle to the data you indeed have good reason to trust it. But the existence of the cycle is what he was trying to demonstrate, it's a tautology to assume it's real to demonstrate that, well, it's real. Indeed, Scafetta correctly first fitted his parabola and then the cycles keeping the parabola fixed. He did not explicitly said he did it this way, I found out empirically.
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  38. HR, that still doesn't change my original point which is this-*if* the Astronomical Cycles Scafetta refers to have acted on the climate before, then we should see *evidence* in the climate record to support it. Now we *do* see evidence of past warming, but this warming was primarily underpinned by a change in the level of Insolation-whether due to increased solar activity (such as the Roman Warm Period & the MWP) or the Earth traversing slightly closer to the sun (the various interglacials). Now if planetary alignments were the actual cause of the change in solar activity, then we'd expect to see increasing solar activity in the current "cycle"-yet the truth is *we're not*-solar activity peaked in the 1940's & has been gradually trending downward ever since. Until someone shows me the some outward *sign* that the sun is being directly impacted by planetary alignments, then Scafetta's work is just an intriguing exercise in mathematical formulations-it most *certainly* isn't a valid explanation for the vast bulk of late 20th century global warming.
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  39. HumanityRules at 15:05 PM on 18 June, 2010

    ”I'm interested in the HADCRUT3 data in fig2. It overall trends up but with periods of rise/fall/rise/fall/rise. Is this not real? Does that need an explanation? This is surely an up trend with a cycle? if not what is the alternative explanation for the phases?

    Surely this is what AGW wants? An a clean uptrend that mirrors the uptrend in CO2 emmissions? Surely AGW wants to remove the mess of interferring factors (such as solar,volcanos and cycles) to leave a nice AGW trend?”


    So many question HR! But you’ve had them answered before I think.

    The 20th century warming trend can be addressed in the manner you speak of, in two essentially equivalent ways by considering the physics involving known forcings and internal variability. Thus one can independently assess the natural contributions to the 20th century and contemporary warming profile and subtract these from the warming profile “to leave a nice AGW trend”. If one does that, then according to Swanson et al (2009) [*] “Removal of that hidden variability from the actual observed global mean surface temperature record delineates the externally forced climate signal, which is monotonic, accelerating warming during the 20th century.”

    The other means of doing this is to model all of the contributions to the 20th century warming profile by parameterizing their contribution according to best estimates using known physics, and assess the extent to which these reproduce the warming profile. A couple of examples of this approach can be found here [**] and here [***]. In this case the “nice AGW trend” is established first according to known physics and included in the model, rather than "falling out" of the model as a remainder left over after removing all the contributions from internal variability a la Swanson et al..

    In all of these cases the essential features of the 20th century and contemporary warming can be understood in terms of rather well understood natural and anthropogenic contributions. It’s not obvious how another phenomenological numerological analysis that lacks a basis in physics and that doesn't anyway match the empirical data very well is going to add to our understanding. That's not to say it isn't interesting. But fundamental scientific steps are missing here, namely (i) a mechanism for the supposed effect, (ii) its independent quantitation, and (iii) some physical explanation of how this "over-rules" all the known physics otherwise described in the papers cited here and elsewhere.


    [*] K. L. Swanson et al. (2009) Long-term natural variability and 20th century climate change. Proc. Natl. Acad. Sci. 106, 16120-16123.

    (see also) Zhang, R., T. L. Delworth, and I. M. Held (2007), Can the Atlantic Ocean drive the observed multidecadal variability in Northern Hemisphere mean temperature? Geophys. Res. Lett., 34, L02709

    [**] Hansen, J. L. et al. (2005) Earth's energy imbalance: Confirmation and implications. Science, 308, 1431-1435

    [***] Lean, J.L., and D.H. Rind, 2008: How natural and anthropogenic influences alter global and regional surface temperatures: 1889 to 2006. Geophys. Res. Lett., 35, L18701
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  40. Chris #39

    Each 'well established' forcing must be looked at in detail - and those from Fig 2.4 of IPCC AR4 are not all that well established.

    Dr Trenberth's 0.9W/sq.m TOA imbalance is derived from "MODELS" - not direct measurement and in particular cooling forcings have wide error bars.

    With little storage in the atmosphere, the integral WRT of the energy flux imbalances ie. heat energy, must show up in the oceans.

    Chris, this “nice AGW trend” is not looking so nice when the purported energy flux imbalances are not showing up in OHC for the last 6 years and probably not much in the last 16 years.

    Unless this 'imbalance' heat shows up in the oceans; warming is not happening and AGW theory is in serious doubt.
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  41. #0 Posted by Riccardo at 07:37 AM
    More generally, for n=4 the claimed 60 year cycle seems to vanish after the peak at year 1940. It's not to say that the n=4 trend has more value than the n=2, but in the end we can say that the nice cyclic behaviour seen in fig. 1 depends on the choice of the trend function. It's worth to recall that its choice is arbitrary, no physics behind it.

    Scafetta might not have provided physical explanation for his choice of n=2, but we can give it a try. If the long term trend described by the polynomial fit is supposed to be a response to the gradual buildup of CO2 in the climate system, and we also accept CO2 can be readily translated to "forcing" (two big IFs, but they are consistent with the mainsrteam consensus), we can make an educated guess about the correct form of the trend; not in detail, but at least about the order of polynomial to be used.

    CO2 increase was more or less exponential starting around 1850 while "forcing" (the resulting radiative imbalance at TOA - Top of Atmosphere) is proportional to its logarithmic concentration. Therefore this forcing has increased in a roughly linear manner since 1850.

    For a small forcing the climate system response can be considered linear. Any reasonable dynamic system should behave like this except for states close to some singularity. However, as climate during the last several thousand years have not shown wide fluctuations and we are still not very far from the average of this timespan, no singularity of the system can be too close to the present state.

    If the response of a linear and time-shift invariant system starts out as x4 for a linearly increasing excitation beginning at some instant (in this case in 1850), then its response to a step function starts as a cubic and for a Dirac delta (a brief pulse) it is quadratic. I am not talking about "climate sensitivity" here, that would involve the long term relaxation properties of the response function, it is all about the initial phase.

    Now. Imagine there was a general balance between incoming SW and outgoing LW radiation at TOA, so the overall balance is neutral. Then, for a brief period (let's say a month or so) this net balance is disturbed, the difference between ASR (Absorbed Shortwave Radiation) and OLR (Outgoing Longwave Radiation) increases substantially, then it is reset to zero again. How does the temperature response look like?

    The key point is that incoming radiative energy, if not reflected immediately back to space gets thermalized soon. If this excess heat is to stay in the system for a while, it has to be stored somewhere. But there is no other way to store it than heating up some part of the system. As there is no substance around with infinite specific heat, it implies an instant temperature increase. However, a quadratic starts from zero and for a while lingers in its vicinity. The initial phase of the impulse response can't be a quadratic, not even linear. It should start with a step.

    Therefore response to a linearly increasing CO2 forcing can only increase as xn if n is not greater than 2.

    I am not saying Scafetta's astrological speculation makes sense, but it can not be rejected on the ground stipulated by Riccardo. You have to find another way to debunk it.

    Of course, as always, there is an alternative. If the underlying trend is not driven by CO2 but by some other secular change capable to increase its forcing in a cubic (as opposed to linear) rate, Scafetta is debunked for good. However, the very existence of this mysterious agent is an immediate death blow to consensus climate science, so if I were you, I would not take the tack.
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  42. I wonder if these astronomical cycles aren't distracting us from those published by Milankovitch.

    For those of you who have never heard of this before, the gravitational effects of other planets "do" affect Earth's orbital shape which changes from circular to elliptical and back over a 400,000 year period. The current shape is almost circular (an even amount of cooking on the spit). A second effect involves the tilt of Earth's axis (determines how different winter is from summer) which is currently 23.4 degrees and decreasing. A third effect involves precession (a wobble) which determines where the Earth's poles points when Earth is nearest the Sun each year. All these effects can be plotted to produce a resultant wave which would enable glaciations every 100,000 years (on average).
    http://en.wikipedia.org/wiki/Milankovitch_cycles

    The world was very skeptical about Milankovitch's theory until evidence for 100,000 year glaciations was found in ice cores from both Greenland (Century Station) and Antarctica (Vostok Station) as well as sediment cores taken from the Indian Ocean (Vema 28-238). Since then, more evidence has come from stalactites and stalagmites as well as other proxies. BTW, the ice cores are good for 400-600k years while the sediment cores provide glaciation evidence going back 700-800k years. In most instances there was an interglacial period lasting 15-20k years.
    http://www.southwestclimatechange.org/climate/global/past-present

    Earth emerged from the previous glaciation about 12,000 years ago. In all previous interglacial periods the temperature rises naturally. Warming oceans begin to release dissolved CO2 into the atmosphere which then acts as a feedback to reinforce the warming cycle (and buffer future changes). The only difference between previous interglacial periods and the current one is that this time, billions of industrial humans have precharged the atmosphere with CO2. As the oceans warm, more oceanic CO2 will be added to industrial CO2 to make things much worse. CO2 emissions from volcanoes can only drive the levels higher.

    { in all these lines I have omitted, but not forgotten, other GH gasses like methane, water vapour, etc. }

    Does this mean that other smaller cycles do not exist? No. I think there is a consensus for solar minimums (Oort, Wolf, Sporer, and Maunder) causing numerous smaller climate coolings in the last 1500 years.
    http://en.wikipedia.org/wiki/Sporer_Minimum

    CO2 levels during the previous glaciation were around 180 ppm but jumped to 280 ppm as we entered the Holocene interglacial. It is now over 380 ppm and I get the feeling that our environment is now immune to future solar minimums. The ice cores also tell us that higher temperatures are always associated with higher levels of CO2. So rather than inspecting charts of "global average temperatures" maybe we should focus a little more on the Keeling Curve.
    http://en.wikipedia.org/wiki/Keeling_curve
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  43. Ken Lambert at 20:58 PM on 18 June, 2010

    "Unless this 'imbalance' heat shows up in the oceans; warming is not happening.."

    That's an extraordinary bit of flawed deductive reasoning Ken. Since global warming clearly is happening (all years of the 2000's warmer than all but one of the 1990's; Jan-May 2010 temperature average the highest on record), even despite the fact that the solar cycle has only just come out of a very prolonged minimum and we're in a supposed cooling ocean fluctuation "cycle"....and sea levels are continuing to rise at a rate that cannot be accounted for by land ice and glacier melt...there's something very wrong with your logic.

    Usually when deductive reasoning leads to conclusions that oppose extant reality, it's pertinent to look at the premises that drive the logic. In your case these are clearly flawed. There is no question that OHC has risen "during the last 16 years". Has OHC stopped rising "for the last 6 years"? Probably not. The sea level data and land ice melt data are incompatible with that conclusion. As usual in science we should wait until these apparent discrepancies have been sorted out before attempting ground-breaking interpretations.....
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  44. Berényi Péter,
    one may always show that a model is wrong using its same logic. Anyways, as you might have anticipated, I looked at GISS radiative forcing and fitted them with similar polynomials. Radiative forcing is quite flat for a while and then increases sharply, a second order polynomial just can't do it. Then, naively looking at radiative forcings as you did reinforced my findings, if anything.

    I didn't talk about it because it is not necessary to show the weakness of the paper and I did not want to see the discussion hijacked by topics like radiative forcings, aerosols, clouds, uncertainties on all of them and the like. I just wanted to show that the astronomical theory does not stand even the slightest scrutiny.
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  45. #44 Riccardo at 21:38 PM on 18 June, 2010
    one may always show that a model is wrong using its same logic

    Huh?
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  46. Berényi Péter,
    Scafetta used an arbitrary trend without discussing it, so did I.
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  47. As expected, Scafetta's paper is used as evidence for the sun being the driver of climate change:
    http://friendsofscience.org/assets/files/documents/2010_June_Newsletter.pdf

    Derek, FoGT
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  48. Chris @39. Heading out of town, so I don't have time to address HR's "points". But I see that you did, excellent job as always Chris, thanks.

    Ken Lambert,

    "Chris, this “nice AGW trend” is not looking so nice when the purported energy flux imbalances are not showing up in OHC for the last 6 years and probably not much in the last 16 years."

    Sigh. Really, why do people feel the need to keep resurrecting long debunked myths. Your "argument" has been addressed here, and specifically in Fig. 1 of Trenberth (2010).

    Climate scientists (e.g., Dr. Latif) have warned us not to expect a monotonic increase in global surface air-temperatures. Yet "skeptics" continue to jump on every perceived short-term slow down or cooling period in the data. Nothing is being hidden here-- the official record is quite noisy, and scientists now know that internal climate variability can be an important modulator of regional temperatures (e.g., NAO, AO, PDO) and some even of global temperatures (e.g., ENSO). Not to mention the short-term impacts of volcanism, and the known (and limited) impacts of the solar cycle.

    That noisy record is one of the reasons why one needs to consider 20-30 years of temperature data to derive a statistically significant trend.

    In addition to the very troubling problems with the paper and method identified by Riccardo: If there is some solar element to this, why does the Stratosphere continue to cool (yes O3 destruction explains some of that cooling but not all of it).

    Also, it would have been useful for Scafetta to quantify the forcing strength of his mechanism in WM-2. How does the strength of this alleged forcing compare to that of CO2? If real, it may have been comparable in the past, but will it be int he future as CO2 forcing continues to escalate?

    If his hypothesis is correct, we should see a marked downturn in global temperatures between until 2018 or so. Personally I have no intention of waiting/delaying another 8 years to (in all likelihood) see this hypothesis falsified, and I doubt very much that policy makers will either.

    Trying to take comfort in the belief that some hitherto undiscovered natural cycle is somehow responsible for the observed warming is not pragmatic, scientific or responsible. Especially when the overwhelming evidence and data points to an significant anthro component.
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  49. #44 Riccardo at 21:38 PM on 18 June, 2010
    naively looking at radiative forcings as you did reinforced my findings, if anything

    I am surprised. Just try the following. As we do not know the correct exponent, look for the best fit using the form a×tξ-b, where ξ is also to be found.

    If you do it for the 160 years between 1850 and 2009, 3.35 (not 4) will be the optimal exponent. However, it is not because the actual trend is accelerating so fast, but because the 60 years long dominant cycle fits 2+2/3 times to this timespan. If you choose an integer multiple of 60, like 1890-2009, the optimal exponent is 1.82. On the other hand if you try to fit the expression to a simple 160 years long sinusoid with a 60 year period, you may get extremely large exponents (depending on phase). Therefore the source of the apparent super-quadratic trend is the cyclic component, not secular change of forcing.

    On top of that the acceleration computed this way seems to diminish with time.

    1850-1969 2.69
    1855-1974 2.29
    1860-1979 2.13
    1865-1984 2.28
    1870-1989 2.11
    1875-1994 2.02
    1880-1999 1.97
    1885-2004 1.99
    1890-2009 1.82


    It's not physics, just plain data analysis. Of course it could be done somewhat more correctly with joint least square fitting of trend and sinusoids, but it is a job for you or Scafetta.
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  50. BP #49

    And that analysis is basically meaningless without some kind of regression analysis. The only way to attribute causality via regression is inductively, by looking at how the error component of the model changes with inclusion and exclusion of various parameters. This helps us to understand the behaviour of the system. My crude statistical analysis of climate data using these kinds of techniques clearly showed that there would have to be evidence of unprecedented quality if CO2 was not to be the main and increasing driver of the current increases in global termperature.
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