Basil Copeland and Anthony Watts
Image from NASA GSFC
Many WUWT readers will remember that last year we presented evidence of what we thought was a “solar imprint” in globally averaged temperature trends. Not surprisingly, given the strong interest and passion in the subject of climate change and global warming, our results were greeted with both praise and scorn. Some problems were pointed out in our original assessment, and other possible interpretations of the data were suggested. Some WUWT readers have wondered whether we would ever follow up on this.
We have been quietly working on this, and having learned much since our initial effort, are as persuaded as ever that the basic premise of our original presentation remains valid. We have tried out some new techniques, and have posted some preliminary trials on WUWT in the past few months, here, and here.
However, questions remain. Since a lot of bright and capable people read WUWT, rather than wait until we thought we had all the answers, we have decided to present an update and let readers weigh in on where we are at with all of this. We have, in fact, drafted a paper that we might at some point submit for peer review, when we are more comfortable with some of the more speculative aspects of the matter. What follows is taken from that draft, with some modification for presentation here.
For those that prefer to read this in printed form, a PDF of this essay is available for download here
Introduction
Evidence of decadal and bidecadal variations in climate are common in nature. Classic examples of the latter include the 20 year oscillation in January temperature in the Eastern United States and Canada reported by Mock and Hibler [1], and the bidecadal rhythm of drought in the Western High Plains, Mitchell, Stockton, and Meko [2], and Cook, Meko, and Stockton [3]. Other examples include a bidecadal (and pentadecadal) oscillation in the Aleutian Low, Minobe [4]; rainfall and the levels of Lake Victoria, East Africa, Stager et al. [5]; and evidence from tree rings along the Russian Arctic, Raspopov, Dergachev, Kolstrom [6], and the Chilean coast, Rigozo et al. [7].
Evidence of decadal or bidecadal oscillations in temperature data, however, especially upon a global scale, has proven to be more elusive and controversial. Folland [8] found a spectral peak at 23 years in a 335 year record of central England temperatures, and Newell et al. [9] found a 21.8 year peak in marine air temperature. Brunetti, Mageuri, Nanni [10] have reported evidence of a bidecadal signal in Central European mean alpine temperatures. But the first to report bidecadal oscillations – of 21 and 16 years – in globally averaged temperature were Ghil and Vautard [11]. Their results were challenged by Eisner and Tsonis [12], but were later taken up and extended by Keeling and Whorf [13, 14].
No less unsettled is the issue of attribution. Currie [15], examining U.S. temperature records, reported spectral peaks of 10.4 and 18.8 years, attributing the first to the solar cycle, and the latter to the lunar nodal cycle. In the debate over the bidecadal drought cycle of the Western High Plains, Mitchell, Stockton, and Meko [2] concluded that the bidecadal signal was a solar phenomenon, not a lunar one. Bell [16, 17] and Stockton, Mitchell, Meko [18] attributed the bidecadal drought cycle to a combined solar and lunar influence, as did Cook, Meko, and Stockton [3]. Keeling and Whorf [13], working with globally averaged temperature data, reported strong spectral peaks at 9.3, 15.2, and 21.7 years. Eschewing a simpler combination of solar and lunar influences, they proposed a complex mechanism of lunar tidal influences to explain the evidence [14].
The past decade has seen only sporadic interest in the question of whether decadal and bidecadal variations in climate have a solar or lunar attribution, or some combination of the two. Cerveny and Shaffer [19] and Treloar [20] report evidence of tidal influences on the southern oscillation and sea surface temperatures; Yndestad [21, 22] and McKinnell and Crawford [23] attribute climate oscillations in the Arctic and North Pacific to the 18.6 year lunar nodal cycle. But interest in discerning an anthropogenic influence on climate has largely eclipsed the study of natural climate variability, at least on a global scale. There continue to be numerous reports of decadal or bidecadal oscillations in a variety of climate metrics on local and regional scales, variously attributed to solar and or lunar periods [3-7, 10, 19-27], but little has been done to advance the state of knowledge of lunar or solar periodic cycles on globally averaged temperature trends since the final decade of the 20th Century.
Besides the shift in interest to discerning an anthropogenic influence on global climate, the lack of agreement on any kind of basic physical mechanism for a solar role in climate oscillations, combined with the apparent lack of consistency in the relation between solar cycles and terrestrial temperature trends perhaps has made this an uninviting area of research. The difficulty of attributing temperature change to solar influence has been thoroughly surveyed by Hoyt and Schatten [28]. In particular, there are numerous reports of sign reversals in the relationship between temperature and solar activity in the early 20th century, particularly after 1920 [28, pp 115-117]. More recently, Georgieva, Kirov, and Bianchi [29] surveyed comprehensively the evidence for sign reversal in the relationship between solar and terrestrial temperatures, and suggested that these sign reversals are related to a long term secular solar cycle with solar hemispheric asymmetry driving the sign reversals. Specifically, they argue that there is a double Gleissberg cycle in which during one half of the cycle the Southern solar hemisphere is more active, while during the other half of the cycle the Northern solar hemisphere is more active. They argue that this solar hemispheric asymmetry is correlated with long term terrestrial climate variations in atmospheric circulation patterns, with zonal circulation patterns dominating in the 19th and early 20th century, and meridional circulation patterns dominating thereafter (see also [30] and [31]).
In our research, we pick up where Keeling and Whorf [13, 14] leave off, insofar as documenting decadal and bidecadal oscillations in globally averaged temperature trends is concerned, but revert to the explanation proposed by Bell [16] and others [3, 18], that these are likely the result of a combined lunisolar influence, and not simply the result of lunar nodal and tidal influences. We show that decadal and bidecadal oscillations in globally averaged temperature show patterns of alternating weak and strong warming rates, and that these underwent a phase change around 1920. Prior to that time, the lunar influence dominates, while after that time the solar influence dominates. While these show signs of being correlated with the broad secular variation in atmospheric circulation patterns over time, the persistent influence of the lunar nodal cycle, even when the solar cycle dominates the warming rate cycles, implicates oceanic influences on secular trends in terrestrial climate. Moreover, while analyzing the behavior of the secular solar cycle over the limited time frame for which we have reasonably reliable instrumental data for measuring globally averaged temperature should proceed with caution, if the patterns documented here persist, we may be on the cusp of a downward trend in the secular solar cycle in which solar activity will be lower than what has been experienced during the last four double sunspot cycles. These findings could influence our expectations for the future regarding climate change and the issue of anthropogenic versus natural variability in attributing climate change.
In our original presentation, we utilized Hodrick-Prescott smoothing to reveal decadal and bidecadal temperature oscillations in globally averaged temperature trends. While originally developed in the field of economics to separate business cycles from long term secular trends in economic growth, the technique is applicable to the time series analysis of temperature data in reverse, by filtering out short term climate oscillations, isolating longer term variations in temperature.
For the mathematically inclined, here is what the HP filter equation looks like, courtesy of the Mathworks
The Hodrick-Prescott filter separates a time series yt into a trend component Tt and a cyclical component Ct such that yt = Tt + Ct. It is equivalent to a cubic spline smoother, with the smoothed portion in Tt.
The objective function for the filter has the form
where m is the number of samples and λ is the smoothing parameter. The programming problem is to minimize the objective over all T1, …, Tm. The first sum minimizes the difference between the time series and its trend component (which is its cyclical component). The second sum minimizes the second-order difference of the trend component (which is analogous to minimization of the second derivative of the trend component).
For those with an electrical engineering background, you could think of it much like a bandpass filter, which also has uses in meteorology:
Outside of electronics and signal processing, one example of the use of band-pass filters is in the atmospheric sciences. It is common to band-pass filter recent meteorological data with a period range of, for example, 3 to 10 days, so that only cyclones remain as fluctuations in the data fields.
(Note: For those that wish to try out the HP filter on data themselves, a freeware Excel plugin exists for it which you can download here)
When applied to globally averaged temperature, the HP filter works to extract the longer term trend from variations in temperature that are of short term duration. It is somewhat like a filter that filters out “noise,” but in this case the short term cyclical variations in the data are not noise, but are themselves oscillations of a shorter term that may have a basis in physical processes.
This approach reveals alternating cycles of weak and strong warming rates with decadal and bidecadal frequency. We confirm the validity of the technique using a continuous wavelet transform. Then, using MTM spectrum analysis, we analyze further the frequency of these oscillations in global temperature data. Using sinusoidal model analysis we show that the frequencies obtained using HP smoothing are equivalent to what are obtained using MTM spectrum analysis. In other words, the HP smoothing technique is simply another way of extracting the same spectral density information obtained using more conventional spectrum analysis, while leaving it in the time domain. This allows us to compare the secular pattern of temperature cycles with solar and lunar maxima, yielding results that are not obvious from spectral analysis alone.
Using the Hodrick-Prescott Filter to Reveal Oscillations in Globally Averaged Temperature
We use the open source econometric regression software gretl (GNU Regression, Econometrics, and Time Series) [34] to derive an HP filtered time series for the HadCRUT3 Monthly Global Temperature Anomaly, 1850:01 through 2008:11 [35].
Figure 1 is representative output in gretl for a series filtered with HP smoothing (λ of 129,000). In the top panel is the original series (in gray), with the resulting smoothed trend (in red). In the bottom panel is the cyclical component. In econometric analysis, attention usually focuses on the cyclical component. Our focus, though, is on the trend component in the upper panel, and in particular the first differences of the trend component. The first differences of a trend indicate rate of change.
By taking the first differences of the smoothed trend in Figure 1, we obtain the series (in blue) shown in Figure 2, plotted against the background of the original data (gray), and the smoothed trend (red).
What does this reveal? At first glance, we see an alternating pattern of decadal and bidecadal oscillations in the rate of warming, with a curious exception circa 1920-1930. We will return to this later. Concentrating for now on the general pattern, these oscillations in the rate of warming are representations, in the time domain, of spectral frequencies in the temperature data, with high frequency oscillations filtered out by the HP smoothing.
As evidence of this, Figure 3 presents the result of two Morelet continuous wavelet transforms, the first (in the upper panel) of the unfiltered HadCRUT3 monthly time series, and the second (in the lower panel) of results obtained with HP smoothing.
The wavelet transforms below a frequency of ~7 years (26.4 ≈ 84 months) are visually identical; the HP filter is simply acting as a low pass filter, filtering out oscillations with frequencies above ~7 years, while preserving the decadal and bidecadal oscillations of interest here. In the next section, we investigate these oscillations in further detail, supplementing our results from HP filtering with MTM spectrum analysis, and a sinusoidal model fit.
Frequency Analysis
Figure 4 is an MTM spectrum analysis of the unfiltered HadCRUT3 monthly global temperature analysis.
A feature of MTM spectrum analysis is that it distinguishes signals that are described as “harmonic” from those that are merely “quasi-oscillatory.” In MTM spectrum analysis a harmonic is a more clearly repeatable signal that passes a stronger statistical test of its repeatability. Quasi-oscillatory signals are statistically significant, in the sense of rising above the background noise level, but are not as consistently repeating as the harmonic signals.
The distinction between harmonic and quasi-oscillatory signals is well illustrated in Figure 4 by the two cycles that interest us the most – a “quasi-oscillatory” cycle with a peak at 8.98 years, and a “harmonic” signal centered at 21.33 years. Also shown are a harmonic, and a quasi-oscillatory cycle, of shorter frequencies, possibly ENSO related. The harmonic at 21.33 years in Figure 4 encompasses a range from 18.96 to 24.38 years, and the quasi-oscillatory signal that peaks at 8.93 years has sidebands above the 99% significance level that range from 8.53 to 10.04 years. These signals are consistent with spectra identified by Keeling and Whorf [13,14].
Figure 5 is an MTM spectrum analysis of the HP smoothed first differences.
The basic shape of the spectrum is unchanged, but it is now well above the background noise level because of the HP filtering. Attention is drawn in Figure 5 to four oscillatory modes or cycles because they correspond to the four strongest cycles derived from using the PAST (PAleontological STatistics) software [36] to fit a sinusoidal model to the HP smoothed first differences.
Shown in Figure 6, the sinusoidal fit results in periods of 20.68, 9.22, 15.07 and 54.56 years, in that order of significance. These periodicities fall within the ranges of the spectra obtained using MTM spectrum analysis, and yield a sinusoidal model with an R2 of 0.60.
Discussion
The first differences of the HP smoothed temperature series, shown in Figure 2 and Figure 6, show a pattern of alternating decadal and bidecadal oscillations in globally averaged temperature. From the sinusoidal model fit, these cycles have average frequencies of 20.68 and 9.22 years, results that are consistent with the MTM spectrum analysis, and with spectra in the results published by Keeling and Whorf [13, 14]. But to what can we attribute these persistent periodicities?
A bidecadal frequency of 20.68 years is too short to be attributed solely to the double sunspot cycle, and too long to be attributed solely to the 18.6 year lunar nodal cycle. There is indeed evidence of a spectral peak at ~15 years, which Keeling and Whorf combined with their evidence of a 21.7 year cycle to argue for attributing the oscillations entirely to the 18.6 year lunar nodal cycle.
But our evidence indicates that the ~15 year spectrum is much weaker, is not harmonic, and probably derives from the anomalous behavior of the spectra circa 1920-1930, something Keeling and Whorf could not appreciate with evidence only from the frequency domain. Especially in light of the evidence presented below, and because the bidecadal signal is harmonic, and readily discernible in the time domain representation of Figure 2 and Figure 6, we believe that a better attribution is the beat cycle explanation proposed by Bell [16], i.e. a cycle representing the combined influence of the 22 year double sunspot cycle and the 18.6 year lunar nodal cycle.
As for the decadal signal of 9.22 years, this is too short to be likely attributable to the 11 year solar cycle, but is very close to half the 18.6 year lunar nodal cycle, and thus may well be attributable to the lunar nodal cycle. Together, the pattern of alternating weak and strong warming cycles shown in Figure 2 and Figure 6 suggest a complex pattern of interaction between the double sunspot cycle and the lunar nodal cycle.
This complex pattern of interaction between the double sunspot cycle and lunar nodal maxima in relation to the alternating pattern of decadal and bidecadal warming rates is demonstrated further in Figure 6 with indicia plotted to indicate solar and lunar maxima. Since circa 1920, the strong warming rate cycles have tended to correlate with solar maxima associated with odd numbered solar cycles, and the weak warming rate cycles with lunar maxima.
Prior to 1920, the strong warming rate cycles tend to correlate with the lunar nodal cycle, with the weak warming rate cycles associated with even numbered solar cycles. The sinusoidal model fit begins to break down prior to 1870. Whether this is a reflection of the poorer quality of data prior to 1880, or indications of an earlier phase shift, we cannot say, though the timing would be roughly correct for the latter. But the anomalous pattern circa 1920, when viewed against the shift from strong warming rate cycles dominated by the lunar nodal cycle, to strong warming rate cycles dominated by the double sunspot cycle, has the appearance of a disturbance associated with what clearly seems to be a phase shift
These results agree with the evidence mustered by Hoyt and Schatten [28] and Georgieva, Kirov, and Bianchi [29] for a phase shift circa 1920 in the relationship between solar activity and terrestrial temperatures. However, we can suggest, here, that the supposed negative correlation between solar activity and terrestrial temperatures prior to 1920 rests on a misconstrued understanding of the data. As can be seen in Figure 6, the relationship between the change in the warming rate and solar activity is still positive, i.e. the warming rate is peaking near the peaks of solar cycles 10, 12, and 14, but at a much reduced level, indicative of the lower level of solar activity during the period. Indeed, for much of solar cycle 12, and all of solar cycle 14, the “warming” rate is negative, but the change in the warming rate is still following the level of solar activity, becoming less negative as solar activity increases, and more negative as solar activity decreases. Still, there is a strong suggestion in Figure 6 of a phase shift circa 1920 in which the relationship between solar activity and terrestrial temperatures changes dramatically before and after the shift. Before the shift, the lunar period dominates, and the solar period is much weaker. After the shift, the solar period dominates, and the lunar period becomes subordinate.
Speculating
To this point, we believe that we are on relatively solid ground in describing what the data show, and the likelihood of a lunisolar influence on global temperatures on decadal and bidecadal timescales. What follows now is more speculative. To what can we attribute the apparent phase shift circa 1920, evident not just in our findings, but as reported by Hoyt and Schatten [28] and Georgieva, Kirov, and Bianchi [29]? While the period of data is too short to do more than speculate, the periods before and after the phase shift appear to be roughly equivalent in length to the Gleissberg cycle.
Since 1920, we’ve had four double sunspot cycles with strong warming rates ending in odd numbered cycles. Prior to 1920, while the results are less certain at the beginning of the data period, there is a reasonable interpretation of the data in which we see four bidecadal periods dominated by the influence of the lunar cycle. These differences may be attributable to the broad swings in atmospheric “circulation epochs” discussed by Georgeiva, et al. [30], characterized either predominantly by zonal circulation, or meridional circulation. With respect to the period of time shown in Figure 6, zonal circulation prevailed prior to 1920, and since then meridional circulation has dominated. These “circulation epochs” may have persistent influence on the relative roles of solar and lunar influence in warming rate cycles.
While the role of variation in solar irradiation over the length of a solar cycle on the broad secular rise in global temperature is disputed, we are presenting here evidence primarily of a more subtle repeated oscillation in the rate of change in temperature, not its absolute level. As shown in Figure 2 and Figure 6, the rate of change oscillates between bounded positive and negative values (with the exception circa 1920 duly noted). Variations in solar irradiance over the course of the solar cycle are a reasonable candidate for the source of this variation in warming rate cycle. As WUWT’s “resident solar physicist”, Leif Svalgaard, has pointed out, variations in TSI over a normal solar cycle can only account for about 0.07°C of total variation over the course of a solar cycle. The range of change in warming rates shown in Figure 2 and Figure 6 are at most only about one-tenth of this, or about ~0.006°C to ~0.008°C. If anything, we should be curious why the variation is so small. We attribute this to the averaging of regional and hemispheric variations in the globally averaged data. On a regional basis, analysis [not presented here] shows much larger variation, but still within the range of 0.07°C that might plausibly be attributed to the variation in TSI over the course of a solar cycle.
So variations in solar irradiance over the course of the solar cycle are a reasonable candidate for the source of this variation in warming rate cycle. At the same time, the lunar nodal cycle may be further modulating this natural cycle in the rate of change in global temperatures. As to the degree of modulation, that may be influenced by atmospheric circulation patterns. With zonal circulation, the solar influence is moderated and the lunar influence dominates the modulation of the warming rate cycles. With meridional circulation, the solar influence is stronger, and the warming rate cycles are dominated by the solar influence.
At this writing, we are in the transition from solar cycle 23 to 24, a transition that has taken longer than expected, and longer than the transitions typical of solar cycles 16 through 23. Indeed, the transition is more typical of the transitions of solar cycles 10 through 15. If the patterns observed in Figure 6 are not happenstance, we may be seeing an end to the strong solar activity of solar cycles 16-23, and a reversion to the weaker levels of activity associated with solar cycles 10-15. If that occurs, then we should see a breakdown in the correlation between warming rate cycles and solar cycles at bidecadal frequencies, and a reversion to a dominant correlation between temperature oscillations and the lunar nodal cycle.
Interestingly, there was a lunar nodal maximum in 2006 not closely associated with the timing of decadal or bidecadal oscillations in globally averaged temperature. This could be an indication of a breakdown in the pattern similar to what we see in the 1920’s, i.e. the noise associated with a phase shift in the weaker warming rate cycles will occur at times of the solar maximum, and the stronger warming rate cycles will occur at times of lunar nodal maximum.
Repeating, there appear to be parallels between our findings and the argument of Georgieva et al. [29] of a relationship between terrestrial climate and solar hemispheric asymmetry on the scale of a double Gleissberg cycle. Solar cycles 16-23, associated as we have seen with increased solar activity, and strong correlations with the strong terrestrial warming rate cycles of bidecadal frequency, represent 8 solar cycles, a period of time associated with a Gleissberg cycle.
While the existence of Gleissberg length cycles is hardly challenged, their exact length and timing is subject to a debate we will not entertain here at any length. Javariah [37] on the basis of the disputed 179 year cycle of Jose [38] believes that a descending phase of a Gleissberg cycle is already underway, and will end with the end of a double Hale cycle comprising solar cycles 22-25.
While it is true that solar activity, as measured by SSN, is already on the decline, we would include the double Hale cycle 20-23 in the recent peak of solar activity, and not necessarily expect to see the bottom of the current decline in solar activity that quickly.
The issue here can perhaps be framed with respect to Figure 7 below:
Assuming we are on the cusp of a downward trend in solar activity that began circa 1990 according to Javariah, and will decline, say, to a level comparable to the trough seen in the early 1900’s, will it be a sharp decline, like that seen at the beginning of the 19th Century, or a more moderate decline like that seen at the beginning of the 20th Century? A naïve extrapolation might be to replicate the more gradual decline seen during the latter half of the 19th Century, suggesting a gradual decline in solar activity through solar cycle 31, i.e. for most of the 21st Century. And based on the prospect of a phase shift in the pattern of decadal and bidecadal warming rate cycles, the bidecadal cycle would come to be dominated by the influence of the lunar nodal cycle, and the influence of the solar cycle would be diminished, leading at least to a reduction in the rate of global warming, if not an era of global cooling.
This is a prospect worthy of more investigation.
Finally, while we readily concede that multidecadal projections are at best little more than gross speculation, in Figure 6 we have carried the sinusoidal model fit out to 2030, and in Figure 8 we use the sinusoidal model of rate changes to project temperature
anomalies through 2030. Assuming a simple projection of the sinusoidal model of rate changes persists through 2030, there would be little or no significant change in global temperature anomalies for the next two decades.
Looking carefully at the sinusoidal model, what we are seeing projected for 2010-2020 are a return to conditions similar to what the model shows for circa 1850-1860, with the period 1853-2020 representing a complete composite cycle of the four combined periods of oscillation. That is, 1853 is the first point at which the sinusoidal model is crossing the x-axis, and at 2020 the model again crossing the x-axis and beginning to repeat a ~167 year cycle. In terms of solar cycle history, that corresponds to a return to conditions similar to solar cycles 10-15, with another phase shift reversing the phase shift of ~1920. If these broad, long term secular swings in solar activity and global atmospheric conditions and temperature anomalies are not random, but reflect solar-terrestrial dynamics that play out over multidecadal and even centennial time-scales, then the early 21st Century may yield a respite from the global warming of the late 20th Century.
Conclusion
There is substantial and statistically significant evidence for decadal and bidecadal oscillations in globally averaged temperature trends. Sinusoidal model analysis of the first differences of the HP smoothed HadCRUT3 time series reveals strong periodicities at 248.2 and 110.7 months, periodicities confirmed as well with MTM spectrum analysis.
Analyzing these periodicities in the time domain with the first differences of the HP smoothed HadCRUT3 time series reveals a pattern of correlation between strong warming rate cycles and the double sunspot cycle for the past four double sunspot cycles. Prior to that, with a phase shift circa 1920, the strong warming rate cycles were dominated by the timing of the lunar nodal cycle.
We suggest that this reversal may be related to a weaker epoch of solar activity prior to 1920, and that we may on the cusp of another phase shift associated with a resumption of such weakened solar activity.
If so, this may result in a reduction in the rate of global warming, and possibly a period of global cooling, further complicating the effort to attribute recent global warming to anthropogenic sources.
References
[1] Mock, SJ, Hibler III, WD. The 20-Year oscillation in Eastern North American temperature records. Nature. 1976; 261: 484–486.
[2] Mitchell, Jr., JM, Stockton, CW, Meko, DM. Evidence of a 22-year rhythm of drought in the western United States related to the Hale solar cycle since the 17th century. In: McCormac, BM, Seliga, TA, editors. Solar-terrestrial influences on weather and climate. Dordrecht, Holland: Kluwer Acad. Publ; 1979. p.125-143.
[3] Cook, ER, Meko, DM, Stockton, CW. A new assessment of possible solar and lunar forcing of the bidecadal drought rhythm in the western U.S. Journal of Climate. 1997; 10:1343-1356.
[4] Minobe, S. Resonance in bidecadal and pentadecadal climate oscillations over the North Pacific: Role in climate regime shifts. Geophysical Research Letters. 1999; 26(7): 855-858.
[5] Stager, JC. Ryves, D. Cumming, BF. Meeker, LD. Beer J. Solar variability and the levels of Lake Victoria, East Africa, during the last millennium. Journal of Paleolimnology. 2005; 33(2):243-251.
[6] Raspopov, OM. Dergachev, VA. Kolstrom, T. .Periodicity of climate conditions and solar variability derived from dendrochronological and other palaeoclimatic data in high latitudes. Palaeogeography, Palaeoclimatology, Palaeoecology. 2004; 209: 127-139.
[7] Rigozo, NR. Nordeman, DJR. Echer, E. Vieira, LEA. Echer, MPS. Prestes, A. Tree-ring width wavelet and spectral analysis of solar variability and climatic effects on a Chilean cypress during the last two and a half millennia. Climate of the Past Discussions. 2005; 1:121-135.
[8] Folland, CK. Regional-scale interannual variability of climate – a north-west European perspective. Meteorological Mazazine. 1983; 112: 163-183.
[9] Newell, NE. Newell, RE. Hsiung, H. and Zhongxiang, W. Global marine temperature variation and the solar magnetic cycle. Geophysical Research Letters. 1989; 16(4): 311–314.
[10] Brunetti, M. Maugeri, M. Nanni, T. Study of the solar signal in mean Central Europe temperature series from 1760 to 1998. Il Nuovo Cimento C. 2003; 26(3): 287-295.
[11] Ghil, M. Vautard, R. Interdecadal oscillations and the warming trend in global temperature time series. Nature. 1991; 350: 324-327.
[12] Eisner, JB. Tsonis, AA. Do bidecadal oscillations exist in the global record? Nature. 1991; 353: 551-553
[13] Keeling CD. Whorf TP. Decadal oscillations in global temperature and atmospheric carbon dioxide. In: Natural climate variability on decade-to-century time scales. Climate Research Committee, National Research Council. Washington, DC: The National Academies; 1996; pp. 97-110.
[14] Keeling CD. Whorf TP. Possible forcing of global temperature by the oceanic tides. Proceedings of the National Academy of Sciences. 1997; 94(16):8321-8328.
[15] Currie, RG. Luni-solar 18.6- and solar cycle 10-11-year signals in USA air temperature records. International Journal of Climatology. 1993; 13(1): 31-50.
[16] Bell, PR. The combined solar and tidal influence on climate. In: Sofia, SS, editor. Variations of the Solar Constant. Washington, DC: National Aeronautics and Space Administration, 1981; p. 241–256..
[17] Bell, PR. Predominant periods in the time series of drought area index for the western high plains AD 1700 to 1962. In: Sofia, SS, editor. Variations of the Solar Constant. Washington, DC: National Aeronautics and Space Administration; 1981; p. 257–264.
[18] Stockton, CW. Mitchell Jr., JM. Meko, DM. 1983: A reappraisal of the 22-year drought cycle. In: McCormac, BM., editor. Solar-Terrestrial Influences on Weather and Climate. Boulder, CO: Colorado Associated University Press; 1983, p. 507–515.
[19] Cerveny, RS. Shaffer, JA. The Moon and El Nino. Geophysical Research Letters. 2001; 28(1): 25-28.
[20] Treloar, NC. Luni-solar tidal influences on climate variability. International Journal of Climatology. 22(12): 2002; 1527-1542.
[21] Yndestad, H. The Arctic Ocean as a coupled oscillating system to the forced 18.6 year lunar gravity cycle. In: Tsonis, AA, Elsner, JB, editors. Nonlinear Dynamics in Geosciences. New York, Springer: 2007; p. 281-290.
[22] Yndestad, H. The influence of the lunar nodal cycle on Arctic climate. ICES Journal of Marine Science. 2006; 63(3): 401-420.
[23] McKinnell, SM. Crawford, WR. The 18.6-year lunar nodal cycle and surface temperature variability in the northeast Pacific. Journal of Geophysical Research. 2007; 112, C02002, doi:10.1029/2006JC003671
[24] Kasatkina, EA. Shumilov, OI. Krapiec, M. On periodicities in long term climatic variations near 68° N, 30° E. Advances in Geosciences. 2007; 13: 25-29.
[25] Yimin, Z. Xiuqun, Y. Joint propagating patterns of SST and SLP anomalies in the North Pacific on bidecadal and pentadecadal timescales. Advances in Atmospheric Sciences. 2003; 694-710.
[26] W. H. Berger, WH. von Rad, U. Decadal to millennial cyclicity in varves and turbidites from the Arabian Sea: hypothesis of tidal origin. Global and Planetary Change. 2002; 34: 313-325.
[27] Zhao, J. Han, Y.-B. Li, Z.-A. The Effect of Solar Activity on the Annual Precipitation in the Beijing Area. Chinese Journal of. Astronomy and. Astrophysics. 2004; 4: 189–197.
[28] Hoyt DV, Schatten, KH. The Role of the Sun in Climate Change. New York: Oxford Univ. Press; 1997.
[29] Georgieva, K. Kirov, B. Bianchi, C. Long-term variations in the correlation between solar activity and climate. Memorie della Società Astronomica Italiana (Journal of the Italian Astronomical Society). 2005; 76(4): 965-968.
[30] Georgieva, K. Kirov, B. Tonev, P. Guineva, V. Atanasov, D. Long-term variations in the correlation between NAO and solar activity: The importance of north–south solar activity asymmetry for atmospheric circulation. Advances in Space Research. 2007; 40(7): 1152-1166.
[31] Georgieva, K. Solar dynamics and solar-terrestrial Influences. In: Maravell, N. ed. Space Science: New Research. New York: Nova Science Publishers. 2006; p. 35-84.
[32] Hodrick, R. Prescott, E. Postwar US business cycles: an empirical investigation. Journal of Money, Credit and Banking. 1997. 29(1): 1-16. Reprint of University of Minneapolis discussion paper 451, 1981
[33] Maravall, A. del Río, A. Time aggregation and the Hodrick-Prescott filter. Banco de España Working Papers 0108, Banco de España. 2001. Available: http://www.bde.es/informes/be/docs/dt0108e.pdf[34] Cottrell, A., Lucchetti, R. Gretl User’s Guide. 2007. Available: http://ricardo.ecn.wfu.edu/pub//gretl/manual/en/gretl-guide.pdf
[35] Brohan, P. Kennedy, J. Harris, I. Tett, S. Jones, P. Uncertainty estimates in regional and global observed temperature changes: a new dataset from 1860. Journal of Geophysical Research. 2006; 111: D12106, doi:10.1029/2005JD006548. Data retrieved at: http://hadobs.metoffice.com/hadcrut3/diagnostics/
[36] Hammer, Ø. Harper, D. Ryan, P. PAST: Paleontological Statistics Software Package for Education and Data Analysis. Palaeontologia Electronica. 2001; 4(1): 9pp. http://palaeo-electronica.org/2001_1/past/issue1_01.htm
[37] Javariah, J. Sun’s retrograde motion and violation of even-odd cycle rule in sunspot activity. 2005; 362(4): 1311-1318.
[38] Jose, P. Sun’s motion and sunspots. Astronics Journal. 1965; 70: 193-200.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
Leif Svalgaard (12:21:45) :
This is my biggest problem with this: ‘where is the 11-yr cycle that is expected: 0.07 degrees? and that countless other papers find.
I addressed part of this in my previous reply. The 11-yr cycle gets “messed up” by the influence of the lunar nodal cycle.
As to the “expected 0.07” degrees, we can get much closer to that in regional temperature variations. I do not have the results handy right now, but I’ve done the same kind of analysis we did here with HadCRUT to the 9 regional US NCDC datasets. I’ve even presented some before here in dialogs with Leif, where I think the decadal variation was on the order of 0.04 degrees. (I’ll see if I cannot dig that up.) Lots of regional variability gets “averaged out” in the global series. Of course, once you start working with regional datasets (like say CET), you often find yourself with completely different periodicities because of the strong influence of atmospheric circulation on regional whether patterns. In a sense, for the solar periodicity, we have the best chance of finding it, it seems to me, in the global data. But the amplitude of the signal is attenuated by the averaging of climate on a global scale.
John S. (11:01:11) :
Gentlemen, you’re on the right track by examining the ROC of the secular sunspot level. That’s where one finds coherence with terrestrial temperatures. You might be on the wrong track, however, in taking HADCRUT3 anomalies as good, consistent estimates of “global average temperature.” Their constructed time-series has highly peculiar features that show up in cross-spectrum analysis with other indices. I realize that there is no other viable alternative if one seeks the longest such series, but a note of caution might be sounded in your splendid presentation.
This is a point well taken. It has been a while, but back when we started all of this, we were using annual data. We applied the method to both HadCRUT and GISS. While there were some notable differences, the basic decadal and bidecadal signals were comparable, as I recall. We might well want to look into that again, at some point.
Very interesting article. However, I feel that because the El Nino/Southern Oscillation (ENSO) is so important to the temperature record, we must address its influence on the cycles that you have found. ENSO is a radiative oscillation, particularly during the 86/7 and 97/8 events. The long-term effects of these events dominate sea surface temperature in the NW Pacific, S Pacific, Indian, and N Atlantic Oceans. I have shown this here:
http://climatechange1.wordpress.com/2009/05/22/ten-questions-for-alarmists-about-the-el-ninosouthern-oscillation/
These long-term step changes can be attributed only to ENSO, so if these step changes are influencing the determined cycle lengths, then there is a problem with the analysis. I also assume that ENSO (not just its after-effects) has a significant impact on the cycle lengths. If this is the case then your analysis suggests that solar/lunar cycles drive ENSO, and that’s a complex case to make.
Good job, gentlemen! This looks like it is the result of a lot of hard work.
So, what exactly is the mechanism that you propose by which lunisolar effects influence temperatures? Is it a lunisolar influence on atmosphere and ocean circulation (which would influence the amounts of energy released from the ocean to the atmosphere over time)? If so, how does that work?
I think I understand your cycle detection analysis, but I am unclear on the mechanism being suggested.
It might be instructive when trying to connect the extra terrestrial causes of climate change from the terrestrial to start by removing the influences of volcanic activity on the recorded signal.
SSSailor (11:59:17) :
Couldn´t find Timo Niroma in the link you gave. Instead, when googled:
Timo Niroma:
http://personal.eunet.fi/pp/tilmari/
http://personal.inet.fi/tiede/tilmari/sunspot4.html
I’ll contribute a little bit to your 1920 change, Anthony.
Observatoire de la Paris reports increased spots per group since 1920.
That would be a solar change.
Solar facinates me.
Weather fascinates me even more.
Could you explain for me, in West Coast terms, what the change from meridonial to zonal will mean for us in California?
I am thinking that it means the storms/fronts will come from due west instead of primarily SW and NW. Would that be correct?
Correct Micheal Crichton link http://sharpgary.org/ChrichtonCommonweal.html
Its definitely worth a read.
I doubt anyone here seriousy believes that sunspots per se drive climate. Indeed, there’s little evidence of a ~11yr cycle in earthly temperatures, except at some (primarily SH) stations. Sunspots are merely a convenient indicator of the activity of that nuclear dynamo we call the Sun. It’s the total activity of our star, not just the TSI, that seems to make an sizable impact through little understood mechanisms. Complex dynamic systems can respond in complicated modes, including harmonic and sub-harmonic ones. The mysterious absence of a ubiquitous 11-yr cycle is no proof positive of lack of solar influence at shorter or–in particular–longer cycles. Even Svalgaard’s crude “power spectra” (actually FFT periodograms with only 2 degrees of freedom, computed as if the sunspot record was periodic ) show considerable “power” at much longer periods, well below the Hale frequency. That’s where I suspect the solar influence really lies. The physical mechanism, of course, is presently unknown.
Next-to-last ppg: “…we seem to BE on the cusp…”? Sorry to be a “nit-n*z*”… all I’m qualified for.
Thanks, Basil! Thanks Anthony!
Best,
Frank
Pamela Gray: You wrote, “the graph looks very SSTish familiar,” referring, I assume, to the “1st Differences Smoothed HadCRUT3 Global Monthly Anomaly” curve.
I would think that curve should look “SSTish familiar”. In effect, the 1st Derivative of HadCRUT3GL is a scaled, very noisy NINO3.4 signal. It’s why a scaled running total of NINO3.4 SST anomalies reproduces the underlying curve of the HadCRUT3GL.
http://i39.tinypic.com/2w2213k.jpg
The graph is from this post:
http://bobtisdale.blogspot.com/2009/01/reproducing-global-temperature.html
I’ve been reading your wonderful site for some time, and wonder how any projections can be accurate if they do not account for the artificially high readings provided by improperly sited sensors?
It seems that temperature readings have been skewed to the high side. Is there a multiplier, for instance all temperatures recorded on land for the past ten years should be reduced by 10%?
Basil:
My strong reservations about HADCRUT3 should by no means be taken as any endorsement of the GISS global anomaly series. Both of these indices, which are indiscriminate in their reliance on urban stations throughout much of the world and shuffle anomalies from an ever-changing set of stations into their yearly compilations, are unsavory data “sausages,” to use John Goetz’s memorable term. Only world-wide averages from a fixed set of UHI-uncorrupted stations can provide an unbiased, consistent estimate. There’s a striking difference in trend and other low-frequency spectral content between such proper averages and the widely-advertised “global anomaly” indices.
If neither the Sun nor the tidal forces acting upon the Earth drive it’s climate, than the climate is nothing more than complex ocillations about a median line.
Accepting that, the Ice Ages are nigh impossible, unless the Sun is going DOWN the H/R diagram instead of up it, or the Earth has not yet finished cooling off from it’s formation and is doomed to be a cold rock. Like Mars.
It’s like the expanding/contracting Universe battle, which has it’s own cycles.
I will not knock anyone who tries to solve the enigma of climate, simply because there are precious few answers.
I will agree that catastrophic doomsday prediction models have for too long taken up too much time, and kept us from making progress.
Pamela Gray @08:38:40
Yes, I can see that the ocean oscillations, or “sloshing-abouts” could be an independant driver, giving their motion is determined to a large extent by the dimensions of the bowls in which they slosh. Lunar would be a big driver of these sloshings, but they would be modulated by the resonant frequencies of these bowls.
It is thus possible that the major lunar cycles would not appear in ocean activity (except for tides, natch) but some little ones could be amplified. I just don’t know enough or have the time to persue this, but without being a “climate scientist” I still have the capacity to apply logic to physical phenomena
I agree with Leif’s skepticism of “cyclomania” but we all accept the “cyclomania” of tide tables. There are also tides in the atmosphere; it is not so unreasonable that there would be lunar effects showing up in “global” temperatures. The problem with “global” measures is that they average out all, and competing, influences.
OK, following is my Necessary Standard Reasonable Statement:
The climate is complex , the strengths, and even mechanisms, of the various influencing factors, are not well understood. Worse still, the actual observational data is of a limited duratiobn and of dubious reliablity.
We just don’t know.
Basil (12:37:58) :
As to the studies showing contradictory results, I think Leif overlooks the “pattern” in these “contradictory” results. If the contradictions were purely random, Leif’s point would be stronger. But their seem to be “runs” in the results, with periodic sign reversals.
The ‘runs’ come about because solar, geophysical, and atmospheric phenomena are not random. but have what in my field is called ‘high positive conservation’ also known as high autocorrelation, so once you get a high there is a good chance that the next data point is also high [at least for a while]. This also decreases the statistical significance very much as the number of independent data points is greatly diminished by high autocorrelation.
The solar/geomagnetic connection with weather/climate is as everybody knows and old one. I’m just now reading from by Ninth edition of Encl. Britt [1878] vol XVI that you have to look for Terrestrial Magnetism is the article about Meteorology where they list [page 179 ff] all the things varying with the sunspots/geomagnetic activity: pressure [Archibald (not that A), Baxendell, Chambers, and so up the alphabet], rainfall [Lockyer, Meldrum, Wex, Stewart, Dawson, Hunter, …], winds and storms [Meldrum, Poey, Jeula, …], temperature [Baxendell, Smyth, Airy, Stone, Koeppen, …]. The conclusion of the article [which was established wisdom in 1878] was that “the sun heats us most when there are fewest spots on its surface”, and then finishes: “This conclusion will not, however, be strengthened if we examine the subject with greater minuteness”. Talk about British understatement 🙂 not to be outdone by the opposite opinion stated in the ‘General Conclusion’ on page 181: “On the whole we may conclude that the meteorological motions and processes of the earth are probably most active at times of maximum of sunspots and that they agree with magnetical phenomena in representing the sun as the most powerful on such occasions, although the evidence derived from meteoology is not so conclusive as that derived from magnetism.”
Not much has changed in the intervening 130 years, it seems. I’m just the reviewer on a paper submitted to a well known journal about the application of continuous wavelet transforms to sunspots and global as well as regional temperatures which concludes that “the recent warming trend can no longer be explained by the level of solar activity”, so it seems that we have not made much progress.
SSSailor (11:59:17) :
The article by Chrichton can be found here.
http://sharpgary.org/ChrichtonCommonweal.html
Nice work…I hope the pay is worth the effort.
Thanks for all the comments and observations. I’ll be addressing some more of them after spending a bit of time watching a movie with the wife.
For those, though, who are a bit unsure of what to make with the HP filter and smoothing, let me assure you that it isn’t the source of the cycles. Those are in the raw data itself. If it helps, pair up Figure 4 with the upper panel of Figure 3, and Figure 5 with the lower panel. Figure 4, and the upper panel of Figure 3, are the raw HadCRUT3 data in all its unfiltered glory. The same basic spectral pattern, in the low frequency data, i.e. the 20.33 and 8.93 yr spectra, are present in both, before and after filtering. The pattern over time of the Morlet transform, at a period of greater than ~2^7 months, i.e. the bottom portions of each panel in Figure 3, are the same. We’ve just filtered out most of the shorter periods.
Astute observers may note, however, that an ENSO likely signal at 4.5 years is there even after filtering. In the Morelet diagrams, that is approximately equal to a value of 2^5.75 months, so if you can visualize a horizontal line on the Morlet transforms at a vertical value of ~5.75, i.e. a little below 5.5, you’ll see that even in the bottom panel of Figure 3, we are picking up the signal at 4.5 years.
Now, just a parting speculation. What’s the source 4.5 year “ENSO cycle,” and where is it in Figure 6? Well, could it just be half of the 9 year cycle? Could the 4.5 year ENSO cycle be a harmonic of the 18.6 yr lunar nodal cycle?
More later.
Basil
Mind boggling stuff – but I can keep things more in perspective when I see this image of the relative sizes of sun, earth and moon rather than your image.
http://www.answersingenesis.org/assets/images/articles/tba/chapter-one/sun-moon-earth.jpg
John S. (15:11:01) :
Basil:
My strong reservations about HADCRUT3 should by no means be taken as any endorsement of the GISS global anomaly series. Both of these indices, which are indiscriminate in their reliance on urban stations throughout much of the world and shuffle anomalies from an ever-changing set of stations into their yearly compilations, are unsavory data “sausages,” to use John Goetz’s memorable term. Only world-wide averages from a fixed set of UHI-uncorrupted stations can provide an unbiased, consistent estimate. There’s a striking difference in trend and other low-frequency spectral content between such proper averages and the widely-advertised “global anomaly” indices.
Have you read the WUWT post on “Comparing the 4 Data Sets”. If so have you seen this plot of the 4 data sets since 1997.
http://jennifermarohasy.com/blog/wp-content/uploads/2009/05/tom-quirk-global-temp-grp-blog.jpg
It seems the satellite measurements are also influenced by the exact same UHI problems.
King of Cool (16:46:34) :
but I can keep things more in perspective when I see this image of the relative sizes of sun, earth and moon rather than your image.
And even more so if the distances were to scale, which would put the Earth about 215 inches = 18 feet over to the right…
I’m traveling at the moment and have very limited Internet access, but I wanted to address Jeremy’s question in the very first comment.
When Basil introduced HP filtering to me last year, I asked the same question: could this be an artifact?
So some tests were run on the algorithm with the same variables used and some datasets there were white noise and well as some pseudo-random generated data to see if we’d get the same periodic outputs.
None were seen, even though I fully expected too see some because I’ve seen similar sorts of behavior in actual electronic bandpass circuits. I was initially very skeptical of the HP filter algorithm, mainly because of its economic roots.
But it seems to have done the job here without intorducing artifacts of its own.
Bob Tisdale (14:58:22) :
Pamela Gray: You wrote, “the graph looks very SSTish familiar,” referring, I assume, to the “1st Differences Smoothed HadCRUT3 Global Monthly Anomaly” curve.
I would think that curve should look “SSTish familiar”. In effect, the 1st Derivative of HadCRUT3GL is a scaled, very noisy NINO3.4 signal. It’s why a scaled running total of NINO3.4 SST anomalies reproduces the underlying curve of the HadCRUT3GL.
Except that the chart she’s looking at, Figure 6 (after she corrected her self), has much of the “noise” you are talking about filtered out. The first differences you would get from the unfiltered HADCRUT3 global series are going to be in the bottom panel of Figure 1, the so-called “cyclical” portion of the HP algorithm. So I would expect to see the “noise” of NINO3.4 in the data that we’ve filtered out.
In a sense, this brings us to where we parted ways on the discussion of the PDO. ENSO probably impacts this out to a decade or so, but beyond that, we’re looking at something else. If you remember the periodograms I did on NINO3.4, there wasn’t a strong signal at a bidecadal frequency like we’re seeing here, or in PDO for that matter. In any event, the point is not that ENSO doesn’t matter. Obviously it does. As I mentioned in my last post, the 4.5 year cycle, which is likely associated with ENSO, may be present in the 9 yr cycle (as a harmonic), and all of this may go back to the lunar nodal cycle, and the solar cycle.