Natural Variation – 60 year cycle

Below is quick review of some of the evidence and consequences of a 60 year climate cycle. According to Roy Spencer, the argument that increasing carbon dioxide concentrations alone are sufficient to explain global warming is reasoning in a circle. By ignoring natural variability, they end up claiming that natural variability is insufficient.

However, the recent paper by Craig Loehle finds only a very small linear warming trend is left (potentially attributable to AGW) after subtracting the 60–70 yr cycle. While cause of the 60yr cycles is unexplained at present, he claims the small trend disproves AGW because it is:

clearly inconsistent with climate model predictions because the linear trend begins too soon (before greenhouse gases were elevated) and does not accelerate as greenhouse gases continue to accumulate with no acceleration in recent decades.

That oscillations are persistent features of the climate has been known for a long time. Stoker and Mysak in 1992 reviewed ice cores, tree-ring index series, pollen records and sea-ice extents over the last 10,000 years, finding:

The traditional interpretation that decadal-to-century scale fluctuations in the climate system are externally forced, e.g. by variations in solar properties, is questioned. A different mechanism for these fluctuations is proposed on the basis of recent findings of numerical models of the ocean’s thermohaline circulation. The results indicate that this oceanic circulation exhibits natural variability on the century time scale which produces oscillations in the ocean-to-atmosphere heat flux. Although global in extent, these fluctuations are largest in the Atlantic Ocean.

Even a paper by Michael Mann in 2000 identifies the cycle:

Analyses of proxy based reconstructions of surface temperatures during the past 330 years show the existence of a distinct oscillatory mode of variability with an approximate time scale of 70 years.

As far back as 1995 Mann published a paper in Nature stating:

THE recognition of natural modes of climate variability is essential for a better understanding of the factors that govern climate change. Recent models suggest that interdecadal (roughly 15–35-year period) and century-scale (roughly 50–150-year period) climate variability may be intrinsic to the natural climate system.

The issue is: How large is the cycle relative to potential warming due to AGW?. Klyashtorin and Lyubushin (2003) demonstrated that a 50–60 year period temperature signal is dominant from about 1650 (the end of the Little Ice Age) in Greenland ice core records, in several very long tree ring records, and in sardine and anchovy records in marine sediment cores. This result was also reported by Biondi et al. (2001), who also made the pithy remark:

Anthropogenic greenhouse warming may be either manifested in or confounded by alterations of natural, large-scale modes of climate variability.

A wide range of phenomena move in sync with this cycle. Long-term changes of Atlantic spring-spawning herring and Northeast Arctic cod commercial stocks also show 50-70-year fluctuations: sufficient to predict the probable trends of basic climatic indices and populations of major commercial fish species for up to 20-30 years into the future.

Zhen-Shan and Xian (2007) found China temperature from 1881 can be completely decomposed into four quasi-periodic oscillations including an ENSO-like mode, a 6–8-year signal, a 20-year signal and also a prominent 60-year timescale oscillation of temperature variation. While they found CO2 concentration contributed a small trend, its influence weight on global temperature variation accounted for no more than 40.19% of the total increase.

Perhaps its all a coincidence. Or perhaps we have yet to see much global warming from CO2, and its all going to suddenly leap out and ambush us in 20 years time.

Maybe, but speculation is a mugs game. Just the facts please. The last 50 years coincides with an upswing in the 60 year cycle, and the recent flat global temperatures coincide with the peak and subsequent downturn.

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0 thoughts on “Natural Variation – 60 year cycle

  1. Thanks, David. A very nice round-up of the studies. Your comment speculation is a mugs game is apt. But the world is rewarding the “mugs”.

    The AGW thesis is a special case of the ‘precautionary principle’: when you have insufficient data, jump the most alarming conclusion (because that’s where the funds/votes are).

    It’s interesting that the Australian government has been at the forefront of rejecting the ‘precautionary principle’ as a decision-function in agreements such as the WTO’s ‘Sanitary and Phytosantiary Measures’ agreement (on quarantine barriers), in the U.N’s ‘Biosafety Protocol’ (on trade in GMOs) and in the Codex Alimentarius (on international food standards and safety). They have repeatedly pointed out in those forums that the ‘precautionary principle’ is non-scientific and amounts to a refusal properly to evaluate available evidence and to take rational measures proportionate to the available evidence.

    Rationality in one domain does not translate, evidently, into another.

    Best wishes,

    Peter

    • Peter, I wonder what would be the distinguishing feature(s) that produce the
      difference in response between those domains?

  2. Thanks, David. A very nice round-up of the studies. Your comment speculation is a mugs game is apt. But the world is rewarding the “mugs”.The AGW thesis is a special case of the 'precautionary principle': when you have insufficient data, jump the most alarming conclusion (because that's where the funds/votes are). It's interesting that the Australian government has been at the forefront of rejecting the 'precautionary principle' as a decision-function in agreements such as the WTO's 'Sanitary and Phytosantiary Measures' agreement (on quarantine barriers), in the U.N's 'Biosafety Protocol' (on trade in GMOs) and in the Codex Alimentarius (on international food standards and safety). They have repeatedly pointed out in those forums that the 'precautionary principle' is non-scientific and amounts to a refusal properly to evaluate available evidence and to take rational measures proportionate to the available evidence.Rationality in one domain does not translate, evidently, into another.Best wishes,Peter

  3. This fits well with my previous identification of two identical warming periods in the twentieth century. I still think an AGW signal could be isolated, but definitely one first has to explain why the 1911-1941 warming occurred at the same rate as the 1978-2008 one.

  4. This fits well with my previous identification of two identical warming periods in the twentieth century. I still think an AGW signal could be isolated, but definitely one first has to explain why the 1911-1941 warming occurred at the same rate as the 1978-2008 one.

  5. Peter, I wonder what would be the distinguishing feature(s) that produce thedifference in response between those domains?

  6. The 60-70 year cycle is clearly evident in the data (see: http://www.appinsys.com/GlobalWarming/ArcticCycles.htm and http://www.appinsys.com/GlobalWarming/GW_Summary.htm

    There is also a longer cycle with an unknown cycle length that is resulting in a net warming after each 60-year cycle.

    An analogy: We have been measuring data each minute for two days now — it went through two warming and cooling cycles and today was warmer than yesterday (the warmest yet observed!). We haven’t observed long enough to see that the days are also on a yearly cycle — each daily cycle is getting warmer in this spring, but eventually there will be net cooling in the longer term cycle.

  7. The 60-70 year cycle is clearly evident in the data (see: http://www.appinsys.com/GlobalWarming/ArcticCycles.htm and http://www.appinsys.com/GlobalWarming/GW_Summary.htmThere is also a longer cycle with an unknown cycle length that is resulting in a net warming after each 60-year cycle.An analogy: We have been measuring data each minute for two days now — it went through two warming and cooling cycles and today was warmer than yesterday (the warmest yet observed!). We haven't observed long enough to see that the days are also on a yearly cycle — each daily cycle is getting warmer in this spring, but eventually there will be net cooling in the longer term cycle.

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