Thursday, December 29, 2011

1246479579.txt

From: Tim Osborn <t.osborn@uea.ac.uk>
To: haozx@igsnrr.ac.cn
Subject: Re: =?gb2312?B?Rnc6IFRpbXMgQW5zd2Vy?=
Date: Wed Jul 1 16:19:39 2009
Cc: Luterbacher J�rg <juerg.luterbacher@giub.unibe.ch>

Dear Zhixin (cc Juerg),
At 15:14 01/07/2009, you wrote:

Do you mean Se should be the standard error from the invidual reconstruction series

yes, that's what I mean.

(before I got your answer, I calculated the standard error for the 5 reconstruction
data at one time point, e.g. 1470s, it is not from the original papers given by the
authors)?

Ah. I understand what you've done now.

But my question is if the author did not publish the uncertainty, how can I deal with
the value of Se?

Well, the original purpose of constructing IPCC Fig. 6.10c was to display the published
uncertainty estimates of each study. If no uncertainties had been estimated by the
original authors then we wouldn't have produced the figure in the first place!
So, do you really want to produce such a figure to show the uncertainty ranges when the
uncertainty ranges haven't been calculated before?
If you do, then you'd need to somehow estimate the uncertainty. You could do this
yourself, perhaps, e.g. from the differences between each reconstruction and the
instrumental temperatures during some overlap (calibration, or independent verification)
period? But this wouldn't measure any increase in uncertainty during periods when each
reconstruction is perhaps based on less input proxy data.
Estimating the uncertainty from the spread of individual reconstruction values in a
particular year, like you've done, is open to criticism. Do you really think that in a
particular year when the three recons have very similar values that the uncertainty is much
less than other nearby years? If you had a high number of independent reconstructions then
this might be ok, but with only 3 series before 1350 it is too susceptible to random
sampling variability.

And now I understood the meaning of 5%-95% range, I will follow this, and replot my
figures with +-1.645SE for the half scores.
Thank you very much again, hopefully I can give the uncertainty of reconstruction
results over China region soon. After finished, may I send the manuscript to you and
give us comments and suggestions?

Yes, that would be fine.
Tim

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