Preprint on climatic regime shifts

Download: Structural break models of climatic regime-shifts: claims and forecasts

Anthony asked if it would be difficult to statistically justify the breaks in temperature between 1976 and 1979 proposed by Quirk (2009) for Australian temperature. He has an interest in oceanographic regime-shifts and climate change. Sure, I said, a simple Chow test.

We ended up rebutting the Easterling & Wehner (2009) claim that describing temperatures since 1998 as declining is ‘cherry picking’, finding a major regime shift occurred in 1997, statistically justifying the use of 1997 as a starting point for temperature trends.

A regime-shift based temperature forecast follows logically from identification of significant breaks. Our paper, “Structural break models of climatic regime-shifts: claims and forecasts“, has been submitted to the International Journal of Forecasting, and is downloadable from arXiv.

article-003

The figure above shows the positions of statistically significant breaks (blue) in 1978 and 1997. Based on the dates of regime-shifts (established with statistical significance and corroborating oceanographic evidence), a presumed underlying warming of 0.5C per century (green line), and no other major changes, the current stable temperature regime will continue until around 2050 until it hits the underlying uptrend, finishing about 0.2C above present temperatures at the end of the century.

This model suggests we are in a period similar to the 50 year period from the 1930’s through to the late 1970’s of very variable, but overall flat temperature trend.
Here is the abstract.

A Chow test for structural breaks in the surface temperature series is used to investigate two common claims about global warming. Quirk (2009) proposed that the increase in Australian temperature from 1910 to the present was largely confined to a regime-shift in the Pacific Decadal Oscillation (PDO) between 1976 and 1979. The test finds a step change in both Australian and global temperature trends in 1978 (HadCRU3GL), and in Australian rainfall in 1982 with flat temperatures before and after. Easterling & Wehner (2009) claimed that singling out the apparent flatness in global temperature since 1997 is ‘cherry picking’ to reinforce an arbitrary point of view. On the contrary, we find evidence for a significant change in the temperature series around 1997, corroborated with evidence of a coincident oceanographic regime-shift. We use the trends between these significant change points to generate a forecast of future global temperature under specific assumptions.

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0 thoughts on “Preprint on climatic regime shifts

  1. Andrew, That is an excellent reference, identical to the Australian situation, and totally supporting our view.

    Finally, the use of trend line analysis in climate
    change research depends greatly upon the time period
    studied, and results can be biased when an abrupt cli-
    mate change is observed during the study period. It has
    been demonstrated that the sudden changes of 1976
    observed in Alaska have a profound effect on tempera-
    ture trends. Shifts and multiyear anomalies result in
    temperature trends over periods that can differ sub-
    stantially (even in sign) from the trend of the full time
    period. The cooling trend throughout much of Alaska
    since 1977, though not statistically significant, is in con-
    trast to some theories regarding the atmospheric warm-
    ing in an increasing greenhouse gas environment.

  2. Andrew, That is an excellent reference, identical to the Australian situation, and totally supporting our view.

    Finally, the use of trend line analysis in climate change research depends greatly upon the time period studied, and results can be biased when an abrupt cli- mate change is observed during the study period. It has been demonstrated that the sudden changes of 1976 observed in Alaska have a profound effect on tempera- ture trends. Shifts and multiyear anomalies result in temperature trends over periods that can differ sub- stantially (even in sign) from the trend of the full time period. The cooling trend throughout much of Alaska since 1977, though not statistically significant, is in con- trast to some theories regarding the atmospheric warm- ing in an increasing greenhouse gas environment.

  3. Hi David, this is a very interesting paper; I have enjoyed it very much today. Have you looked at the work of Tsonis et al. 2007 and other papers that also discuss the ‘climate shift’ of the 1970s? Does this connect or could it connect with the Tsonis theory?

    • I have. He is much more simulation physics based, though he does think that major climate shifts can contribute to warming, with an underlying AGW, so its along the lines of our forecast.

  4. Hi David, this is a very interesting paper; I have enjoyed it very much today. Have you looked at the work of Tsonis et al. 2007 and other papers that also discuss the 'climate shift' of the 1970s? Does this connect or could it connect with the Tsonis theory?

  5. I haven’t read the paper but…you are scaring me now. Calling a trend that has gone on for 10 years and saying it will go on for 40 more (and shift then)? You sound some some sort of chartist technical analyst stock picker (and those guys are total shiite.

    • Careful reading would suggest that they are fully aware of the limitations of their analysis-lots of uses of “presumably” and “assumptions”

      I do hope that they’ll keep us appraised of how their “forecast” is doing (I note that it seems to yield results very similar to the standard “baseline” method which one evaluates forecast skill against, namely “no change”). My guess is that it is to simplistic to do very well but they note that in the paper itself.

      • The EnE thing is scaring me too. I have a (well informed) Bayesian prior about things going into that journal instead of normal ones…

      • I know the quality in EnE is variable. But it had some advantages for the Rahmstorf note. It is quick. It publishes short notes. The one published was sent back by the editor of another journal because it was too short. But I thought it didn’t need to be any longer, for people who know the context.

      • The Rahmstorf note was fine. Already said that. Kudos. Appreciate your agreement with the poor quality and allowance of poor quality at EnE. I was referring to the other paper, not to Rahmstorf note.

      • I doubt that we will keep appraised. If you believe the temperature measurements from 1930-80 they are higher variance than after that. If the climate change involves a change in the mean AND the variance, and we are in a period like 1930-80, then its going to be a longer time before there is proof of stability.

    • 1. not being called on technicals alone, the fundamentals (oceanic) support the call as well.
      2. the typical half period of this PDO thing is around 50 years. Its in the residuals when you fit a line. This is no more of an assumption that fitting a periodic term, as many do.

      • 1. “not on technicals alone”. Technicals is CRAP. It is a JOKE. No serious economist has any truck with it. The ghost of Milton Freidman comes out of the grave to beat you silly. No widows peaks and candle sticks allowed. Go read your Brealey and Myers.

        2. wtf. We don’t have enough data to rule out ltp, but we do have enough data to rule in a PDO?

        We skeptics need to STOP buying into silliness. Need to stop giving a lower hurdle to crap that we like than crap we don’t like. Heck, look at Watts with his solar silliness.

        Pu-leeze. Be a baller. Kick the AGWers in the head when they do something wrong. But don’t be going around with wish fullfillment judgments like Briggs calling the election for McCain when Tradesports had it at 9-1 Obama. Sheesh.

      • I don’t disagree. Why not RTFP? I check two papers, one a sceptic I guess and one not, then the forecast is in the last part in the sense of, “if this is real then this follows”.

  6. I haven't read the paper but…you are scaring me now. Calling a trend that has gone on for 10 years and saying it will go on for 40 more (and shift then)? You sound some some sort of chartist technical analyst stock picker (and those guys are total shiite.

  7. Careful reading would suggest that they are fully aware of the limitations of their analysis-lots of uses of “presumably” and “assumptions”I do hope that they'll keep us appraised of how their “forecast” is doing (I note that it seems to yield results very similar to the standard “baseline” method which one evaluates forecast skill against, namely “no change”). My guess is that it is to simplistic to do very well but they note that in the paper itself.

  8. The EnE thing is scaring me too. I have a (well informed) Bayesian prior about things going into that journal instead of normal ones…

  9. 1. not being called on technicals alone, the fundamentals (oceanic) support the call as well.2. the typical half period of this PDO thing is around 50 years. Its in the residuals when you fit a line. This is no more of an assumption that fitting a periodic term, as many do.

  10. I know the quality in EnE is variable. But it had some advantages for the Rahmstorf note. It is quick. It publishes short notes. The one published was sent back by the editor of another journal because it was too short. But I thought it didn't need to be any longer, for people who know the context.

  11. 1. “not on technicals alone”. Technicals is CRAP. It is a JOKE. No serious economist has any truck with it. The ghost of Milton Freidman comes out of the grave to beat you silly. No widows peaks and candle sticks allowed. Go read your Brealey and Myers. 2. wtf. We don't have enough data to rule out ltp, but we do have enough data to rule in a PDO? We skeptics need to STOP buying into silliness. Need to stop giving a lower hurdle to crap that we like than crap we don't like. Heck, look at Watts with his solar silliness. Pu-leeze. Be a baller. Kick the AGWers in the head when they do something wrong. But don't be going around with wish fullfillment judgments like Briggs calling the election for McCain when Tradesports had it at 9-1 Obama. Sheesh.

  12. The Rahmstorf note was fine. Already said that. Kudos. Appreciate your agreement with the poor quality and allowance of poor quality at EnE. I was referring to the other paper, not to Rahmstorf note.

  13. I don't disagree. Why not RTFP? I check two papers, one a sceptic I guess and one not, then the forecast is in the last part in the sense of, “if this is real then this follows”.

  14. I mean the one from EnE that you cited. Which I can’t read anyhow. Not paying for it and strangely enough my free access to the vast majority of journals does not extend to that exemplar of insights: EnE.

    I will check out your paper.

  15. I mean the one from EnE that you cited. Which I can't read anyhow. Not paying for it and strangely enough my free access to the vast majority of journals does not extend to that exemplar of insights: EnE.I will check out your paper.

  16. I have. He is much more simulation physics based, though he does think that major climate shifts can contribute to warming, with an underlying AGW, so its along the lines of our forecast.

  17. I doubt that we will keep appraised. If you believe the temperature measurements from 1930-80 they are higher variance than after that. If the climate change involves a change in the mean AND the variance, and we are in a period like 1930-80, then its going to be a longer time before there is proof of stability.

  18. FWIW, since 1976 no cyclone has crossed the east coast of Australia south of the tropic of Capricorn whereas prior to this it was commonplace and often several times per year.It didn't stop happening gradually, it just stopped happening.

  19. FWIW, since 1976 no cyclone has crossed the east coast of Australia south of the tropic of Capricorn whereas prior to this it was commonplace and often several times per year.It didn't stop happening gradually, it just stopped happening.

    • Hi, As we do not claim that the existence of breaks refutes global warming, the claim that these articles explore, the articles have little to do with the paper.

      What is relevant is whether the method used is sufficiently robust to represent actual regime shifts.  As the methods in the links find shifts in random data, they show the methods they have chosen are inadequate.  Largely this is because the have chosen a model that forces step changes.  We don’t do that.  The model is free to fit a slope, or two slopes.

      Showing lousy, inappropriate methods find spurious breaks, as these guys do, does not refute a more appropriate method that is less prone to errors.  

      The purpose of our paper is to examine specific claims, such as Easterling’s claim there is no possibility of a regime shift, and that temperatures are continuing to increase at the same rate.  Our analysis shows there is evidence of a break, a regime shift, for whatever reason, and so the claim that temperature increases have paused does have statistical basis.  

      But you need a Chow test broken regressions at least and even more rigor to really address the question of statistically significant breaks.  Not just fit steps to the data.

    • Barry, Sorry about the delay.  I wanted to write a post on it but have not had time.  The issue I would have with T’s rebuttal are the he seems quite incurious about the coincidence between the well documented changes in ocean circulation in bout 1976 and in 1998 (as cohenite linked to and others in my paper).

      He acknowledges that the Chow test is appropriate, but then wrongly says that I believe the break model, when it is quite clear that the break analysis is used in hypothesis testing mode, not modelling mode.  

      The specific claims we made were: Quirk (that there was a break in 1976 – affirmative), and that their was a break in the continuous upward trend in temperatures (contradicting Easterling’s assertion).  The fact that T had to factor out ocean indicators in his recent paper, in order to recover an underlying continuous upward trend, seems to demonstrate that Easterlings’s assertion was statistically incorrect, and so T has had to try to fix it.  

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