Comments on: Fleitmann 2007: "Observed Anti-Correlation"

By: UC

UC — Sat, 30 Jul 2011 20:29:40 +0000

The figure in here now, http://www.climateaudit.info/data/uc/Ebisuzaki_cce.png (cref http://noconsensus.wordpress.com/2011/07/27/123-2/ )
Calibration should be done locally, but not sure how to combine the resulting non-normally distributed outputs to a global average. Median tree -approach (once you’ve seen one tree…) might actually work well.

By: UC

UC — Sat, 11 Apr 2009 18:50:32 +0000

Re: Dave Dardinger (#139),

Which means the reconstruction can't be used to rule out the null hypothesis that there's been no temperature rise in the past 2k years.

Correct. Statements such as in Mann08,

Our results extend previous conclusions that recent Northern Hemisphere surface temperature increases are likely anomalous in a long-term context.

are based on unrealistic CIs. M&M reply made it clear.

By: Dave Dardinger

Dave Dardinger — Thu, 09 Apr 2009 21:48:27 +0000

Re: UC (#138), Looks to me like if you draw a line through 0 (and lots of other values) well over 95% of the values are within the 95% envelope. Which means the reconstruction can't be used to rule out the null hypothesis that there's been no temperature rise in the past 2k years.

By: UC

UC — Thu, 09 Apr 2009 20:14:11 +0000

Re: Geoff (#137),

Nice picture.

I think it's ok, given the quality of scientifically published reconstructions. Pros: Proxy screening was done locally, by using published method, without restrictive AR(1)-noise assumption. Calibration result and CIs are obtained using Brown82 equations. Cons: Local proxy vs. global temperature calibration No dynamic model for temperature applied Some proxies used might have some problems ( search CA )

By: Geoff

Geoff — Thu, 09 Apr 2009 11:09:26 +0000

Re: UC (#136), Nice picture. It sure give me confidence (limits).

By: UC

UC — Thu, 09 Apr 2009 10:08:38 +0000

Re: UC (#135),

I’ll check how many of Mann08 proxies survive this test..

It seems that only

1070 tornetrask
1061 tiljander_2003_darksum

survive this test in the early steps. At AD1400 step there following proxies get through:

271 ca630
272 ca631
287 cana106
314 cana175
362 co556
397 fisher_1996_cgreenland
424 gisp2o18
628 mo037
654 mt110
778 nm560
796 norw010
820 nv516
908 schweingruber_mxdabd_grid1
909 schweingruber_mxdabd_grid10
910 schweingruber_mxdabd_grid100
920 schweingruber_mxdabd_grid11
927 schweingruber_mxdabd_grid12
933 schweingruber_mxdabd_grid18
934 schweingruber_mxdabd_grid19
935 schweingruber_mxdabd_grid2
936 schweingruber_mxdabd_grid20
937 schweingruber_mxdabd_grid21
938 schweingruber_mxdabd_grid22
959 schweingruber_mxdabd_grid42
960 schweingruber_mxdabd_grid44
961 schweingruber_mxdabd_grid45
977 schweingruber_mxdabd_grid6
988 schweingruber_mxdabd_grid70
1002 schweingruber_mxdabd_grid89
1070 tornetrask
1061 tiljander_2003_darksum
1104 ut509
1122 vinther_2004_scgreenland
427 haase_2003_srca
330 chuine_2004_burgundyharvest

Leave Tiljander out, calibrate with iHAD_NH_reform: http://signals.auditblogs.com/files/2009/04/cce.png ..

By: UC

UC — Wed, 08 Apr 2009 12:24:39 +0000

Thanks Geoff, I’ll take a look.

But before going to sea level business, here’s the interesting thing:

This method is published in high-quality journal, and used by sea level experts. Why wouldn’t Mann use it for testing significant correlations in proxy vs. temperature series? Because it gives critical r values that are in the range of 0.2 – 0.3 ? I’ll check how many of Mann08 proxies survive this test..

By: Geoff

Geoff — Wed, 08 Apr 2009 04:56:40 +0000

Re: UC (#133), You may also want to look at the presentation by Leuliette here (Pdf file).

By: UC

UC — Tue, 07 Apr 2009 13:28:59 +0000

While trying to learn how uncertainties in sea level changes are computed, I found this paper :

http://sealevel.colorado.edu/MG_Leuliette2004.pdf

wherein it is said that

This from of bootstrapping is robust when the residuals are serially correlated, as is the case for mean sea level (Ebisuzaki 1997)

The paper cited is:

Wesley Ebisuzaki: A Method to Estimate the Statistical Significance of a Correlation When the Data Are Serially Correlated, Journal of Climate, Volume 10, Issue 9 (September 1997)

and I even found the Matlab code :
http://www.ldeo.columbia.edu/~kja/access/code/ebisuzaki.m

Then I tried the code with data in #94

and got the result

Creating synthetic time series…
Performing Monte Carlo significance test
—
Observed correlation coefficent: 0.20057
Fraction of |coefficients| larger than Observed: 0.117 [Threshold Value:0.05]

Critical R Value: 0.24506

Critical R is quite close to the value I computed in #119 , where I knew how the process was made. Not bad!

By: UC

UC — Mon, 29 Dec 2008 21:03:49 +0000

Re: Hu McCulloch (#131),

Did you invent the sqrtm(MI) method, or has this been around? If it’s new you should definitely publish it somewhere other than on CA!

I did invent it. Then I mentioned the method to one math professor, who said it’s trivial. That happens all the time Yet, I have something to publish from CA work, and that won’t go to climate science journal.

My home computer has an old version 4 of Matlab, on which sqrtm(MI) is very slow, not to mention inaccurate, for n = 512. Version 5+ works much faster and accurately, so the computational practicality of your sqrtm(MI) method is a relatively recent thing.

I wrote more efficient, recursive way, to compute that matrix. Will clean it up and email.