2011-07-26 04:55:35Climate sensitivity low, it's oscillations, new paper Loehle and Scafetta, peer reviewed
grypo

gryposaurus@gmail...
173.69.56.151

The Open Atmospheric Science Journal

 

 

Climate Change Attribution Using Empirical Decomposition of Climatic DataCraig Loehle and Nicola Scafetta

 

 

Discussion at Judy's

 

FROM ABSTRACT:   About 60% of the warming observed from 1970 to 2000 was very likely caused by the above natural 60-year climatic cycle during its warming phase. A 21st Century forecast suggests thatclimate may remain approximately steady until 2030-2040, and may at most warm 0.5-1.0°C by 2100 at the estimated0.66°C/century anthropogenic warming rate, which is about 3.5 times smaller than the average 2.3°C/centuryanthropogenic warming rate projected by the IPCC up to the first decades of the 21st century. However, additionalmultisecular natural cycles may cool the climate further.

 

This one is surely to excite the crowds!

2011-07-26 05:18:54
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

Thanks grypo, at least I think so....

I'm sure the discussion at Judith's is riveting and very scientific ;) 

Yes, it will excite the crowds-- of course it was designed to do just that. Now we have to all wait on taking action until 2030-2040 ;)

They conlcude that CS for doubling CO2 is 1.0 to 1.5 C.....uh huh.

This paper belongs in the fiction section.

2011-07-26 05:19:32
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

Passed it on to Tamino...

2011-07-26 05:31:271.0 to 1.5? Seriously?
Daniel Bailey
Daniel Bailey
yooper49855@hotmail...
24.213.18.68

What is it about Judy's blog that inspire's such high comedy?

2011-07-26 05:49:02
grypo

gryposaurus@gmail...
173.69.56.151

Well, Scafetta's astro-cycles (that nobody else can figure out) are involved, so this will likely be ignored by people with real acedemic creds, but the first blog debunk is in!

 

Craig, anytime someone tries to simply make a lame ‘plausibility’ argument by assertion rather than physics, I am instantly suspicious. Scafetta’s SCMSS curve (from which the 60 years cycle is ‘drawn’) is the speed of the sun around the barycenter of the solar system. But the sun is in free fall (as are the other bodies in the solar system) and it is well known that a body in free fall feels no forces associated with its trajectory. This is a very old result and one that fatally undermines any purported physical mechanism.

One could perhaps argue that tidal forces (which are felt) matter but these can be calculated very precisely and are a) very small, and b) associated with Mercury and Venus, not Jupiter and Saturn. And they are not related to the speed of the sun in any case (and note that the distance from the barycenter (CMSS) doesn’t have any power in the 60 year band in any case).

indeed, reading Scafetta’s early work on this, it is clear that the ’60 year’ cycle was first seen by him in the temperature record and it was only subsequently that he found some astronomical reason to use it in a decomposition. It is worth pointing out that no aspect of the astronomical series other than the period is being used here.

As for your solar curve, it is made up of a hodge podge of uncalibrated and unrelated indices. A 1-2 smooth of the SCL? Pray tell what theory or empirical calibration supports its use as a TSI proxy? And then adding an 11 year cycle to it???? What does that even mean? Then you average it with Wang Lean and Sheely *and* Hoyt and Schatten (which by the way includes SCL as one of it’s inputs). This is completely ad hoc.

And then you just extend out a linear trend for the projection. Why? If you think the trend to date is related to various forcings, isn’t it more likely that the trend in the future will follow those forcings? And why do you compare the trend from 1940 to today with projections of IPCC models for the 21st Century? This is completely incommensurate.

This might be a published paper, but that does not mean it was worth publishing.

2011-07-26 05:54:46
dana1981
Dana Nuccitelli
dana1981@yahoo...
64.129.227.4

Oh goody two of my favorite deniers, Scafetta and Loehle.  Anyone know anything about The Open Atmospheric Science Journal - like it is obscure or prominent?

This paper looks very similar to Akasofu's approach.  Fit some random cycle to the data and subtract it out.  The only difference is that Akasofu calls the remaining trend 'LIA recovery', whereas these two at least call it anthropogenic warming.  Or maybe just part of it...

"Fig. (3A, B) show that about 50 +/- 10% of the 0.8oC global surface warming observed from 1850 to 2010 is likely the result of a natural warming trend recovery since the LIA plus the combined effects of 20- and 60-year natural cycles."

2011-07-26 06:11:51
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

Grypo @5:49,

 

Ouch!  Beautifully done, did Carig reply?  I really can't bring myself to go there....

2011-07-26 06:21:42
dana1981
Dana Nuccitelli
dana1981@yahoo...
64.129.227.4

Loehle's reply:

"You are free to have your own opinion."

Brilliant.  Scafetta's reply:

"Our study is simple. A 60 year cycle has been detected in numerous climate data and solar data covering records as long as millennia. Just read our paper and thereferences there. Moreover, it is a clear astronomical cycle known since ancient times.

There is nothing simpler than interpreting a time series that contain detectable cycles. If you have valid arguments, please argue them."

In short, "there appears to be a 60 year climate cycle; we randomly varied its amplitude in a curve fitting exercise, and called it science."

2011-07-26 06:27:37
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

Well Loehle's defense was compelling ;)  People tend to say things like that when they have NOTHING.

2011-07-26 06:38:20
dana1981
Dana Nuccitelli
dana1981@yahoo...
64.129.227.4

Loehle pretty clearly hasn't got a clue (what else is new?).  I'm not sure how he ended up as lead author on this paper.  It seems like mostly Scafetta's work.

Would be nice to extrapolate their model backwards.  I bet it shows much larger temperature changes pre-1860 than the proxy data indicates.

Regardless, we really should do a post in response to this paper.

2011-07-26 08:22:47
Rob Honeycutt

robhon@mac...
98.207.62.223

Yeesh!  Tamino's going to destroy this paper.

2011-07-26 08:36:35
grypo

gryposaurus@gmail...
173.69.56.151

Oh you all need to go through that Curry thread to read the responses.  It's actually hysterical.  Loehle thinks he's found more evidence for low climate climate sensitivity "consistent with Spencer and Lindzen", even though neither of those two have found this evidence.  Scafetta repeats the "science isn't settled" mantra, essentially having no argument agains the flaw in curve fitting different trnds and the inability to show the physical basis for this nonsensical explanation of temp trends. 

I don't feel ashamed for laughing....

they knew quite well about a 60-year astronomical cycle related to Jupiter and Saturn. Just do some google search.

  • The first result is from an astrology site:
    http://www.astrologyweekly.com/dictionary/jupiter-cycle.php

    But this appears to be numerology: 3 times the repeat period? Why is that more important than the repeat period itself? or twice or half or 4 times?

    And if this is the source of your cycle, what time series does this actually refer to? What does it have to do with speed of the sun around the barycenter?

    I think it’s far more likely that you are just casting around for a cycle that matches something you have decided is in the temperature data. Thus a ‘match’ is not at all coincidental.

2011-07-26 08:49:25
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

Look at Scafetta's home page.  Look at his affiliation:

"Active Cavity Radiometer Irradiance Monitor (ACRIM lab) & Department of Anesthesiology"

For crying out loud...."Anesthesiology"?!  Sad that just about anyone feels like they can just waltz in and undertake meaningful climate science nowadays.

2011-07-26 09:11:22
dana1981
Dana Nuccitelli
dana1981@yahoo...
64.129.227.4

Well, Scafetta has done a lot of solar research (hence his affiliation with ACRIM).  He's certainly more qualified than Loehle.

2011-07-26 09:30:05
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

Hi Dana,

Scafetta may have undertaken a lot of solar reserarch, not denying that, but what was the quality of said research? 

2011-07-26 09:37:21
dana1981
Dana Nuccitelli
dana1981@yahoo...
64.129.227.4

Some of it has certainly been crappy quality.  This same type of behavior, trying to fit certain parameters to the data to make the solar influence seem larger than it actually is, as a matter of fact.

2011-07-26 09:37:50
Rob Honeycutt

robhon@mac...
98.207.62.223

"A 21st Century forecast suggests thatclimate may remain approximately steady until 2030-2040..."

Hmmm...  Based on this line alone this paper should be relatively short lived.

It's a great candidate for a future "past predictions" post. 

2011-07-26 11:01:21
rustneversleeps
George Morrison
george.morrison2@sympatico...
99.232.158.68
If you read the paper back to front (an unfortunate habit, heuristic, I confess), they certainly cast a wide net - ref. 77 is an apparent dismissal of the Rockstrom et al 2009 paper on "Planetary Boundaries"... Yeah, I know, they mentioned 350ppm in that paper, but wtf as the closing line in this paper????
2011-07-26 14:10:24
dana1981
Dana Nuccitelli
dana1981@yahoo...
69.230.106.238

Have a look at the formula for their model:

y (t) = Temp Anomaly = A cos[2 pi (t-T1)/60] + B cos[2 pi (t-T2)/20] + C (t-1900) + D

Obviously the two cosine functions (which are their 60 and 20 year cycles) will just oscillate with amplitudes of A and B.  D is just a constant, so basically their model has global temperature increasing infinitely as time progresses due to that third linear term.  I don't see them trying to identify the physical cause of that term.  The anthropogenic term is the residual.

I guess they would argue that the formula only applies over the past 150 years.  Except then they use it to project future temperature changes.  I don't see any reason to believe their third term will continue linearly, since they don't seem to identify the physical cause (unless I'm missing it).  Oh, that's probably their "recovery from the LIA" term.

It's just hard to get anything out of a paper with so little physics.  They just waive their hands and say "look, magical natural cycles fit the data pretty well".  I really don't like curve fitting exercises like this.  Tamino would call it "mathturbation".

2011-07-26 14:25:31
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

Dr. Gavin Schmidt has weighed in:

 

"Magnus W says:

I guess you have seen this… how it got past review beats me.

An other curve fitting exercise:
http://benthamscience.com/open/toascj/articles/V005/74TOASCJ.pdf

“A 21st Century forecast suggests that climate may remain approximately steady until 2030-2040, and may at most warm 0.5-1.0°C by 2100 at the estimated 0.66°C/century anthropogenic warming rate, which is about 3.5 times smaller than the average 2.3°C/century anthropogenic warming rate projected by the IPCC up to the first decades of the 21st century. However, additional multisecular natural cycles may cool the climate further.”

[Response: I love the way that even the abstract compares two completely different things (the trend from 1950? and 21 st century projections) as if they were the same period. Maybe they think this is justified because there is a law of nature that says that linear trends have to continue indefinately...? This is just embarrassing. - gavin]

Sadly, Loehle and Scarfetta seem quite proud of their mathurbation.

2011-07-26 14:57:05
dana1981
Dana Nuccitelli
dana1981@yahoo...
69.230.106.238

Yeah true, their assumption that the linear warming rate will continue is wholly unsupported too (other than noting the logarithmic relationship between T and CO2).  But their sensitivity is so low, there's probably not a big difference between linear and exponential anthropogenic warming in their model.

I'll probably do a post on this paper this weekend, so if you have any more thoughts, keep 'em coming.  There are a lot of problems with the paper to discuss.

  • Their suggested physical mechanisms (astronomical orbital cycles and "LIA recovery") have no physical basis for impacting global temps
  • They have 4-6 different model parameters which they simply allow to vary with no physical basis or justification (a.k.a. curve fitting, graph cooking, and mathturbation)
  • They ignore all natural forcings, assuming that solar + volcanic forcings have also caused a linear warming trend (their "LIA recover" third term), which is simply not true (see Meehl 2004 - if anything these forcings have declined since 1950)
  • If their results were correct, it would mean aerosols have virtually no impact on global temperature.  It fails to explain observed global dimming and brightening, though in a blog comment Loehle threw out some nonsense about cosmic rays causing a 'haze'.
  • They assume the linear anthropogenic warming trend will continue at its current rate
  • They ignore anthropogenic effects pre-1950, though if their low sensitivity were correct, that wouldn't be a major omission.  But that pre-supposes a low sensitivity.

Anything else?

2011-07-26 16:13:08
Rob Painting
Rob
paintingskeri@vodafone.co...
118.92.35.182

What sort of journal let's the authors trot out "skeptic" zombie arguments that aren't even analysed in the paper?

- I see the UHI meme. Just thrown out there.

- The Houston and Dean bogus SLR paper "the measured deceleration of the sealevel rise from 1930 to 2010 occurred despite the strong positive acceleration of anthropogenic GHG emissions during the same period." - Rahmstorf and Vermeer have debunked that.

Figure 5 is a classic. Like you point out Dana, they just have the Earth warming indefinitely. Considering that Loehle did that piss-poor MWP reconstruction, what about running their model back in time to the MWP? 

2011-07-26 16:54:49
Dikran Marsupial
Gavin Cawley
gcc@cmp.uea.ac...
139.222.14.107

Even the first line of the abstract is a fail

"About 60% of the warming observed from 1970 to 2000 was very likely CAUSED by the above natural 60-year climatic cycle during its warming phase."

correllation is not causation, so it is a logical error to claim a causal relationship on the basis of a curve fitting exercise.

BTW Bentham journals are not prestigeous places to publish, they are so obscure that IIRC they once asked me to edit one of their journals, which puts things into perspective quite nicely! ;o)

2011-07-26 21:43:54Anything else?
grypo

gryposaurus@gmail...
173.69.56.151
????

Even assuming the rest of the paper to be correct, there seems to be a problem with the model-fitting.

In Fig. 2b of the paper (reproduced above as Fig. 1b), C&S argue that the residuals prior to 1942 are random, so that the 60+20 model is justified for the early period. For the later period (1942-2010), they add an additional linear trend to create a separate model. However, they do not show a graph of the residuals, which likewise must be random for the later model to be valid.

Inspection of the afore-mentioned figure (1b above) shows that the residuals are mostly positive during 1950-1975, are mostly negative during 1975-2002, and are mostly positive since 2002. This is precisely the same residual pattern (positive, then negative, then positive over the period of validity of the model) that causes C&S to reject their original ‘entire period’ model shown in Fig. 1 of their paper.

So, their model for the period 1950-2010 appears to fail their own test for validity, and should not be used to infer attribution of climate change since 1950 nor to create future projections of climate change. The failure of the model post 1950 also raises the question of whether the good behavior prior to 1950 was a matter of chance.

2011-07-26 21:53:24
grypo

gryposaurus@gmail...
173.69.56.151

Rob,

Figure 5 is a classic. Like you point out Dana, they just have the Earth warming indefinitely

 

I imagine the (silly) explanation for that is here:

 

Properconsideration of these cycles and of longer natural cycles isalso critical for detecting underlying trends. For example, amillenarian or longer period cycles might explain the patternof the Medieval Warm Period and Little Ice Age (Loehle andSinger [32]) as well as warming since about 1800.

 

This paper is like a blind guessing game, looking for physical basis' for changes.  I'll file it under 'anything-but-CO2-please' attribution.  Leif at WUWT calls it 'cyclomania at it's worst'.  hahahaha.

2011-07-26 22:06:07
grypo

gryposaurus@gmail...
173.69.56.151

This from RC may help with questions about the publisher here:

 

Charlessays:

Re: 341

Magnus, the reason that the paper got through, uh, peer review might be found in the following links:
http://www.earlham.edu/~peters/fos/2009/09/criticism-of-oa-publisher-bentham.html
http://www.earlham.edu/~peters/fos/2009/06/hoax-exposes-incompetence-or-worse-at.html

[Response: They are also publishing completely garbage such as the latest missive from Gerhard Kramm on the "so-called greenhouse effect". Oh dear. - gavin]

 

I think this thread is enough for Dana's blog post.  Too much actually...

2011-07-27 02:08:14
dana1981
Dana Nuccitelli
dana1981@yahoo...
64.129.227.4

Hehe yeah grypo, like I said, there are soooo many issues with this paper, the post is going to take a while to draft up!  Good points from Rob, Dikran, and John N-G.

I'm going to try to run their model backwards to see what it looks like near the MWP.  It's obviously going to look like crap since they have that linear trend - it's just going to go straight downwards.  Might be reasonable for the LIA, but not the MWP.

I might actually make this a 'lessons from past climate predictions' series entry, but instead of examining future projections, examine how their model fits past data.

2011-07-27 04:11:53
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

Dana,

WHich case are you thinking os using 1 or 2 (plus residula linear trend).  I cannot belive that they simply added a fudge factor after 1942 for case 2-- surely I have that wrong!? McIntyre must be feverishly auditing their paper right now.

2011-07-27 04:15:50
dana1981
Dana Nuccitelli
dana1981@yahoo...
64.129.227.4

I'll use their Case 2.  That's the one they claim is accurate - Case 1 they admit the residuals don't look good.  Of course for Case 2, as commenters noted, they didn't look at the residuals after they fit the linear trend do the post-1950 data.  But that's the basis of their low sensitivity and low projected warming claims.

2011-07-27 04:21:56Spencer again
dana1981
Dana Nuccitelli
dana1981@yahoo...
64.129.227.4

By the way, apparently Spencer has been at his simple model curve fitting again as well.  Barry Bickmore has another excellent post about it, which would make a great lead-in to a post on L&S (I've asked him if we can re-post it here).  Their approaches (use a simple model which ignores actual forcings, use a whole bunch of parameters with no physical constraints, and play "let's fit the curve") are almost identical.

2011-07-27 04:47:15
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

Thanks Dana.  A 60-yr cycle eh?   This time they attribute the mystical cycle to something going on in the cosmos, or aether of space or something, anything but anthro GHGs and aerosols.  Sigh.

You are going to have fun with this one aren't you? :)  So is Tamino...

2011-07-27 05:24:53
Riccardo

riccardoreitano@tiscali...
93.147.82.83

It's a strange sum of arbitrary assumption, none of them unrealistic though quite unlikely and rather crude. The difference from the other Scafetta's paper is the breaking of the background in two separate linear segments; the older is still unattributed. Non much of an improvement.

As for the support to the 60 years cycle, they write: "Ogurtsov et al. [50] found strong evidence for the cycle, such as a 60 to 64 year period in 10Be, [...]"
in Ogurtsov et al 2002  a 64 years cycle in 10Be is at best sporadic during the last 900 years (fig. 4) and absent in the last couple of centuries.
h/t Neil's comment @ Curry's

2011-07-27 05:40:26
dana1981
Dana Nuccitelli
dana1981@yahoo...
64.129.227.4

Yeah Riccardo, I debated whether to look over all of the papers L&S reference regarding the 60 year cycle to see if they're representing them accurately, especially in light of the misrepresentation of Ogurtsov.  I think it's a relatively minor point, given that they're claiming the cycle is astronomical in origin to begin with.  Maybe there's a minor 60 year climate cycle, but it's not caused by Jupiter's orbit, or whatever ridiculous thing Scafetta proposed.  More likely it's associated with PDO or something like that.  But then of course you run into the problem with failing to explain the simultaneously warming oceans, which is probably why they're trying to find some sort of external astronomical forcing.

The early century trend they did suggest was probably mainly solar plus some volcanic forcing, by the way.  They made no attempt to quantify or support that assumption, but did mention it as a potential cause.  They also didn't explain why that early century trend should have continued in the late 20th century, or into the future.  They sort of wrote it off as "LIA recovery" like Akasofu did, which is kind of a strange contradiction (on the one hand blaming specific forcings, on the other hand blaming some nebulous "recovery").

2011-07-27 06:06:40
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

Dana,

While I have your attention and talking about mathurbation.  Here is another forecast to debunk (H/T to Rattus and Google)-- look at their Figure 2.23 on page 54.  Look familiar?

Also  interesting this is the site which links to their paper, America's Independent Party. The stuff of fiction I tell ya.

2011-07-27 06:51:55
dana1981
Dana Nuccitelli
dana1981@yahoo...
64.129.227.4

The link doesn't work for me Alby.  Sends me to some weird page in Russian I think.  If you can get to the paper, maybe you can download it an email to me?

2011-07-27 06:55:00
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

Dana,

Paste this into your browser window:

http://alexeylyubushin.narod.ru/Climate_Changes_and_Fish_Productivity.pdf

 

2011-07-27 09:31:35
dana1981
Dana Nuccitelli
dana1981@yahoo...
64.129.227.4

Ah yes, another one arguing that the planet cooled during 1940-1970, and assumes it was caused by 'natural cycles'.  No mention of aerosols is made.  Good find there Albie.

That's a weird combination to write a report about - Cyclic climate changes and fish productivity.

2011-07-27 14:37:02
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

Had this paper by Loehle and Scafetta been subjected to actual peer-review by someone in the know, I imagine this is what they would have said to the authors:


"Sir[s] I am sitting in the smallest room of my house. I have your manuscript in front of me. Soon it will be behind me." [I think that that quote originated with Voltaire]

2011-07-27 15:00:06Comment
Robert Way

robert_way19@hotmail...
142.162.17.242

I have a few issues with the paper also that are nitpicks more or less. Firstly their model is fitting a temperature dataset that is already forced by volcanic eruptions. I mean they are fitting to the temperature record that has been significantly changed (particularly in the early stages) because of large scale volcanic eruptions. Without that forcing their model performs weaker. Secondly, they`re using hadley. I have a lot of issues with the constant use of hadley because it undersamples the warming and does no provide an adequate picture of large scale temperature changes especially going that far back. I don`t trust their data from 1850s to 1900 and I don`t think that curve fitting on 50 years of poor quality temperature data is a worthwhile enterprise. (Especially SSTs).

Furthermore they don`t test how their model would perform against different temperature records and deal with the issue of calibration. I just submitted my first paper yesterday and I hope that it gets as easy a review as these guys got :P

2011-07-27 15:06:55
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

Good luck with the paper Robert. Does this mean that your thesis is going to be journal format? 

2011-07-27 15:14:40Comment
Robert Way

robert_way19@hotmail...
142.162.17.242

This is actually unrelated to my thesis. This is regarding work during my Bachelor at U of O. If it would interest you, I could send along a copy of the submission (keep it to yourself of course). It is submitted to International Journal of Climatology.

Beyond that though, yes my thesis will be journal format. I am expecting two papers that should each be publishable. One will be an inventory of glaciers in the Torngat Mountains of northern Labrador and a second will be on the timing of the little ice age and glacier changes since that time to present (2007 being present).

2011-07-27 15:23:26
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

Thanks for clarifying Robert.   Going the journal route worked for me-- it kept me focussed both in terms of the content/subject matter and the time line.  It was also nice to have already addressed the concerns raised by the reviewers when it came to my defense.

Whether or not I bother you to send the mauscript to me depends on what the paper is about....we are in quite different fields.  That reminds me, I have reviewed for IJCL, but not in your field. They seem to be pretty fair, and have a fairly quick turnover between submission and going to press.  Publishing in Canada's Atmosphere-Ocean, now that was pretty tough.

2011-07-27 15:26:36Comment
Robert Way

robert_way19@hotmail...
142.162.17.242

This paper is regarding multi scale climate variability in the Labrador region of northeastern Canada. Essentially just establishing links between certain climate indices and the regions temperature changes on an annual timescale. That sort of thing. Plus I developed a station combination method (similiar to BEST) that we used for it.

2011-07-28 06:33:12
dana1981
Dana Nuccitelli
dana1981@yahoo...
64.129.227.4

Good points Robert.  Funny how all the "skeptics" are exclusively using HadCRUT these days.  I'll mention your points in the post.

2011-07-28 09:26:35
rustneversleeps
George Morrison
george.morrison2@sympatico...
70.54.239.226
Is it overkill to mention that their "cycles-numerology" with no proposed explanatory physics would not only have to explain global mean temperature increases but ALSO the greenhouse signature of the observed changes? (thinking while reading John's "experiment" post)
2011-07-28 10:38:43
dana1981
Dana Nuccitelli
dana1981@yahoo...
12.186.216.66
No actually that's a very good point - one that I like to mention when talking about alternative theories, so thanks for the reminder.
2011-07-28 12:02:17
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

Good point Rust...one that continues to ellude Spence too I might add.

2011-07-30 08:19:40
dana1981
Dana Nuccitelli
dana1981@yahoo...
69.230.106.190

I tested their model by running it backwards and comparing to Moberg.  As I expected, it matches the LIA pretty darn well because of that linear trend component, but then blows up prior to about 1500.  Here's the money shot:

L&S failure

2011-07-30 08:27:30
Alex C

coultera@umich...
67.149.101.148

Is this the same 60 year cycle that Scafetta found in the paper Riccardo did a post on here?  Why did Scafetta use a parabolic trend to find that cycle and use a linear one here?

2011-07-30 08:39:37
dana1981
Dana Nuccitelli
dana1981@yahoo...
69.230.106.190

Yep, same cycle (thanks for pointing that out, by the way).  They probably used a linear trend because of their assumptions - that the warming up to ~1950 was natural, and was anthropogenically accelerated after ~1950.  They argued that the recent trend is linear, and cited a couple papers to support that argument.

In short, it's just a different curve fitting approach.  But they did at least make an attempt to justify it.

2011-07-30 09:25:08
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

Oh dear, that is bad. 

One problem I see iwith your figure Dana is that the Moberg data are for the N. Hmeisphere terrestrial SAT data, whereas IIRC their model is for global SATs....

Has anyone used a simple model, GHG forcing, aerosols and TSI to try and reconstruct the global SAT going back 2000 years?  It would be nice to contrast this with such a paper's findings.

Do they provide any caveat concerning the validity of their model?  Do they state anywhere that this cycle only emerged at the beginning of their study.  If not, they are sunk.

2011-07-30 12:22:43
Rob Painting
Rob
paintingskeri@vodafone.co...
118.93.130.247

Dana - beautiful mate! That sure is one powerful image. Can I suggest rather than labelling it "L&S Model", you label it "Loehle & Scarfetta (2011) model. Be good to get that image circulated around the blogosphere. 

2011-07-30 12:27:58
Alex C

coultera@umich...
67.149.101.148

>>> They argued that the recent trend is linear, and cited a couple papers to support that argument.

I have yet to read the paper, but you simply CANNOT determine a 60 year cycle from 60 years of data.  The initial cycle was determined by detrending at least 120 years of data, and that was a parabolic fit.  This is a major problem with analysing residual trends for cyclical patterns, you have to correctly remove the underlying trend (and various noise) and must make sure the behavior of your trend over given time intervals does NOT change half-way through your analysis.  Did they properly do this?

I'm going to read the paper.

 

Edit: It seems like I am correct, they referene Scafetta's 2010 paper [18] which is the exact one that used the parabolic fit to determine the residuals.  Let's remember from Riccardo's post that the cycles virtually fall apart when you apply a linear trend.  How can they possibly, then, apply those cycles with a linear fit (the C(t-1900) term) with any sort of justification?

2011-07-30 15:25:55
dana1981
Dana Nuccitelli
dana1981@yahoo...
69.230.106.190
Albie - just about every millennial temp reconstruction is of the NH. There just aren't enough SH proxies to make a good global reconstruction. But I had thought of that, and will mention it in the post. Even though L&S is global, it still should be reasonably close to Moberg's (or any other) NH reconstruction. Rob - thanks, and good suggestion. An easy fix which I'll do tomorrow. Alex - the tricky thing is that in this paper, they're applying a second linear fit to the residuals in their Case 2. But I'm also making the point in the post that they never evaluated the residuals in Case 2. They rejected Case 1 (just one linear trend) because the residuals were non-random. If you eyeball the residuals in Case 2 (two linear trends), they're pretty clearly not random either. Someone made this point in a blog post comment on Curry's, I think, and Loehle's response was that it looked random to his eyeballs. But they didn't actually do the analysis in the paper. That's how they got away with it - just sloppy. The paper really should't have been published. I'm also going to have a brief discussion of the Bentham Open journals in the post, sort of as an explanation as to how this horrid paper got published at all.
2011-07-30 15:28:03
dana1981
Dana Nuccitelli
dana1981@yahoo...
69.230.106.190
I got about half of the post done today, by the way. So I'll have a draft up for review sometime tomorrow. I covered the big points already, now just have to go back and list the many, many other (but less important) problems with the paper.
2011-07-30 16:52:32
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

Hi Dana,

No worries. I am awre of the scaricty of SH Hemi. proxies.