Swanson's PC Projection

Swanson’s projection for future temperature using presumed regime shifts can be compared with our projection.

rc_fig1_thumb

The above figure was posted at RealClimate (note this figure is not contained in their paper) with flat temperature intersecting with an extrapolated underlying rate of around 1C/Century seen between 1950 and 1998 at around 2020.

article-003

Our projection for temperature, from figure 3 of our paper archived at arXiv and submitted to IJF, Structural break models of climatic regime-shifts: claims and forecasts is based on the current flat rate intersecting with an extrapolated underlying rate of around 0.5C/Century between 1910 and 1976, at around 2050.

Which is more valid? Our reasoning is that if you are to accept that temperatures are being suppressed in a -ve phase of the PDO, then they must have been enhanced in a +ve phase from 1976 to 1998. Therefore, it is invalid to take the underlying rate of warming from 1976 to 1998.

Sure, assuming the higher rate of underlying warming fits the climate models, IPCC and AGW alarmism story better, but I can’t see the logic in it. Note also its inconsistent with the trend line from 1976 in their paper (below) which intersects around year 2000 (compare with first figure above).

swanson

Moreover, all of the empirical estimates of climate sensitivity (not the climate model ones) come in at an underlying warming rate closer to 0.5C/century, as the figure below from Roy Spencer illustrates.

spencer_fig1_models-reality1

Are these inconsistent? Swanson says (inaccurately, its actually from 1950, doh!) of the presumed underlying warming trend:

Also shown is a linear trend using temperatures over the period 1979-1997 (no cherry picking here; pick any trend that doesn’t include the period 1998-2008). We hypothesize that the established pre-1998 trend is the true forced warming signal, and that the climate system effectively overshot this signal in response to the 1997/98 El Niño.

In other words, Swanson isn’t committed. But the figure prepared for the RealClimate post chose a period corresponding the the highest rate of warming, consistent with the climate models, but internally inconsistent with their assumption that the current plateau in temperatures is due to regime shift.

We picked a period corresponding to a consistent view of regime-shifts both enhancing and suppressing the underlying trend, and also consistent with empirical measurements of climate sensitivity.

On the face of it, it looks like logical consistency and empirical evidence, versus agreement with the climate models and damn the logic and evidence – a politically correct projection?

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0 thoughts on “Swanson's PC Projection

  1. Hi David,

    I made this post at Chris Colose’s blog earlier and because I fear it will not be discussed properly there I’m interested to see how it goes here (slightly corrected in one point):

    I was alerted to the Tsonis et al. 2007 theory in a paper by Lindzen (2007, “Taking Greenhouse Warming Seriously”) where he interpreted the theory as such: “A very recent paper (Tsonis et al., 2007) suggests, in fact, that the surface temperature record can be accounted for by essentially superpositions of known oceanic fluctuations such as the Pacific Decadal Oscillations and the Atlantic Multidecadal Oscillations.”

    I then read the Tsonis et al. 2007 paper and found that Lindzen’s interpretation of it was quite reasonable. That is, very little could be found there to reassure the IPCC that their Summary for Policymakers explanation of the so-called “unprecedented” global warming period 1976-1998 was caused entirely by increasing GHGs with 90% certainty (in fact, that it probably offset what would otherwise have been a period of cooling, IPCC2007, SPM, p. 5).

    So Swanson’s appearance the other day at RealClimate came as a huge surprise to me. I was surprised that RealClimate would touch anything like this, other than to show that it was thoroughly discredited after enough big-name skeptics had started citing it (and I don’t think many have), and I was even more surprised to then hear Swanson’s view of the paper that there was no inconsistency with the IPCC version at all.

    So I fixed upon the following issue, which appeared to be the slight-of-hand that allowed him to assert this apparently self-contradictory position: I saw that in that RealClimate post he just draws a straight line through the trend of 1976-1998, the so-called unprecedented bit, and then extends it all the way back to 1850, shows how it fits all the data in a vaguely convincing way, and then asserts that this is the underlying GHG signal. He also asserted that it wasn’t cherry-picking, and that I’d get the same trend using any endpoints I could choose other than one inside 1998-2008(??).

    Here’s the problem: I am not a statistician, but in what sense can the rise of 1976-1998 be called “unprecedented” if it is the same trend that fits all the data all the way back to 1850? It wouldn’t be unprecedented anymore, would it. It’d be quite normal.

    I think this is a big problem, and I’m looking forward to your response.

    All sorts of similar questions arise to this bizarre Swanson disavowal, and I am afraid, I just cannot believe he really believes himself what he’s just written. I guess that’s my earlier point about how you can say anything on a blog, even if you’re a published scientist, and get past the peer-review, i.e. it really cuts both ways.

    If you agree with my post, given I’m not even a scientist & you have a Ph.D in statistics, it seems really strange that a lay person can see this, whereas Ph.D climate scientists apparently can’t…

  2. Hi David, I made this post at Chris Colose's blog earlier and because I fear it will not be discussed properly there I'm interested to see how it goes here (slightly corrected in one point):–I was alerted to the Tsonis et al. 2007 theory in a paper by Lindzen (2007, “Taking Greenhouse Warming Seriously”) where he interpreted the theory as such: “A very recent paper (Tsonis et al., 2007) suggests, in fact, that the surface temperature record can be accounted for by essentially superpositions of known oceanic fluctuations such as the Pacific Decadal Oscillations and the Atlantic Multidecadal Oscillations.”I then read the Tsonis et al. 2007 paper and found that Lindzen’s interpretation of it was quite reasonable. That is, very little could be found there to reassure the IPCC that their Summary for Policymakers explanation of the so-called “unprecedented” global warming period 1976-1998 was caused entirely by increasing GHGs with 90% certainty (in fact, that it probably offset what would otherwise have been a period of cooling, IPCC2007, SPM, p. 5).So Swanson’s appearance the other day at RealClimate came as a huge surprise to me. I was surprised that RealClimate would touch anything like this, other than to show that it was thoroughly discredited after enough big-name skeptics had started citing it (and I don’t think many have), and I was even more surprised to then hear Swanson’s view of the paper that there was no inconsistency with the IPCC version at all.So I fixed upon the following issue, which appeared to be the slight-of-hand that allowed him to assert this apparently self-contradictory position: I saw that in that RealClimate post he just draws a straight line through the trend of 1976-1998, the so-called unprecedented bit, and then extends it all the way back to 1850, shows how it fits all the data in a vaguely convincing way, and then asserts that this is the underlying GHG signal. He also asserted that it wasn’t cherry-picking, and that I’d get the same trend using any endpoints I could choose other than one inside 1998-2008(??).Here’s the problem: I am not a statistician, but in what sense can the rise of 1976-1998 be called “unprecedented” if it is the same trend that fits all the data all the way back to 1850? It wouldn’t be unprecedented anymore, would it. It’d be quite normal.I think this is a big problem, and I’m looking forward to your response.All sorts of similar questions arise to this bizarre Swanson disavowal, and I am afraid, I just cannot believe he really believes himself what he’s just written. I guess that’s my earlier point about how you can say anything on a blog, even if you’re a published scientist, and get past the peer-review, i.e. it really cuts both ways.–If you agree with my post, given I'm not even a scientist & you have a Ph.D in statistics, it seems really strange that a lay person can see this, whereas Ph.D climate scientists apparently can't…

  3. “it seems really strange that a lay person can see this, whereas Ph.D climate scientists apparently can't…” Beats me too. GRL is a joke. Check out IJF sometime.

  4. You know, I would really love to see this Kiehl 2007 paper on climate models and their ability to simulate that ol' 'aerosols caused the global cooling of the 70s' storyline discussed in connection with this Swanson & Tsonis 2009 theory.Kiehl, J. T. (2007), Twentieth century climate model response and climate sensitivity, Geophys. Res. Lett., 34, L22710, doi:10.1029/2007GL031383.https://www.atmos.washington.edu/twiki/pub/Main…This paper (cited in Lindzen 2009, “Climate Science: Is it currently designed to answer questions?”, ArXiv) is only 4 pages long, mostly readable by non-specialists, and asks some VERY interesting questions, given that these questions are coming from an IPCC person like Jeffrey Kiehl…

  5. Swanson’s post at RC says “The figure to the left shows the spatial mean temperature over all grid boxes in the HadCRUT3 data set that have continuous monthly coverage over the 1901-2008 period.”

    Requiring all grid boxes used to have no missing months is a pretty strict standard. I have Giss station data from a couple years ago and I could find only 77 stations world-wide that would qualify with perfect data through 2006. 52 of those are US. I realize they used Hadcrut instead, but it makes me wonder what percentage of global coverage they actually achieved. I think qualifying ocean grid-cells would also be pretty sparse. I suspect their coverage ended up being less than 25% of the globe. But I’m not interested enough to thoroughly check.

    I downloaded a Giss table of global temperature anomalies and calculated the yearly changes. The 1998 temperature increase, although substantial, at 0.17C it wasn’t even a 2 sigma event.(+/-0.22C change in one year) There was a 2 sigma temperature decrease in 1999 that immediately wiped out all the 1998 increase and most of the 1997 increase.

    There are seven 2 sigma temperature changes in the Giss record. Temperature increases in 1957 & 1977. Temperature decreases in 1890, 1964*, 1974, 1992*, and 1999. (* volcano?)

    Here is a graphic. http://i30.tinypic.com/10o1vz5.gif

    I don’t see how they can say there is anything being stored ‘in the pipe-line’ that is going to somehow appear a decade or so down the road.

    The 32 year trend lines sure look to me like a little natural warming being alternately depressed then enhanced by the PDO every half cycle.

  6. Swanson's post at RC says “The figure to the left shows the spatial mean temperature over all grid boxes in the HadCRUT3 data set that have continuous monthly coverage over the 1901-2008 period.”Requiring all grid boxes used to have no missing months is a pretty strict standard. I have Giss station data from a couple years ago and I could find only 77 stations world-wide that would qualify with perfect data through 2006. 52 of those are US. I realize they used Hadcrut instead, but it makes me wonder what percentage of global coverage they actually achieved. I think qualifying ocean grid-cells would also be pretty sparse. I suspect their coverage ended up being less than 25% of the globe. But I'm not interested enough to thoroughly check.I downloaded a Giss table of global temperature anomalies and calculated the yearly changes. The 1998 temperature increase, although substantial, at 0.17C it wasn't even a 2 sigma event.(+/-0.22C change in one year) There was a 2 sigma temperature decrease in 1999 that immediately wiped out all the 1998 increase and most of the 1997 increase.There are seven 2 sigma temperature changes in the Giss record. Temperature increases in 1957 & 1977. Temperature decreases in 1890, 1964*, 1974, 1992*, and 1999. (* volcano?)Here is a graphic. http://i30.tinypic.com/10o1vz5.gifI don’t see how they can say there is anything being stored ‘in the pipe-line’ that is going to somehow appear a decade or so down the road.The 32 year trend lines sure look to me like a little natural warming being alternately depressed then enhanced by the PDO every half cycle.

  7. Swanson's post at RC says “The figure to the left shows the spatial mean temperature over all grid boxes in the HadCRUT3 data set that have continuous monthly coverage over the 1901-2008 period.”Requiring all grid boxes used to have no missing months is a pretty strict standard. I have Giss station data from a couple years ago and I could find only 77 stations world-wide that would qualify with perfect data through 2006. 52 of those are US. I realize they used Hadcrut instead, but it makes me wonder what percentage of global coverage they actually achieved. I think qualifying ocean grid-cells would also be pretty sparse. I suspect their coverage ended up being less than 25% of the globe. But I'm not interested enough to thoroughly check.I downloaded a Giss table of global temperature anomalies and calculated the yearly changes. The 1998 temperature increase, although substantial, at 0.17C it wasn't even a 2 sigma event.(+/-0.22C change in one year) There was a 2 sigma temperature decrease in 1999 that immediately wiped out all the 1998 increase and most of the 1997 increase.There are seven 2 sigma temperature changes in the Giss record. Temperature increases in 1957 & 1977. Temperature decreases in 1890, 1964*, 1974, 1992*, and 1999. (* volcano?)Here is a graphic. http://i30.tinypic.com/10o1vz5.gifI don’t see how they can say there is anything being stored ‘in the pipe-line’ that is going to somehow appear a decade or so down the road.The 32 year trend lines sure look to me like a little natural warming being alternately depressed then enhanced by the PDO every half cycle.

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