From	Eystein Jansen	Date	Wed, 30 Aug 2006 21:43:25 +0200
To	Keith Briffa
CC	Jonathan T. Overpeck
Subject	Fwd: Chpt 6 - last 1000 yrs
Hi Keith, John should have the latest versions of the comments file and the chapter text, i.e. the ones that went out for LA review this summer. I believe he is after some more specific answers in the comments and not so much changes to the text, and has selected the bristlecone issue, the divergency issue and the verification and robustness issues. If you are unsure what comments or tetx he refers to, I think the best thing is for to ask John for the specific comments he thinks are not adequate, or the specific lines of text which he suggests changed. It seems he needs some reassurance rather than you writing much new in terms of comments and text, so the best would be to talk to him and ask what he needs you to do to the documents. Best wishes, Eystein Envelope-to: Eystein.Jansen@geo.uib.no Date: Wed, 30 Aug 2006 15:31:12 +0100 To: Eystein Jansen From: Keith Briffa Subject: Fwd: Chpt 6 - last 1000 yrs X-UEA-Spam-Score: -101.6 X-UEA-Spam-Level: --------------------------------------------------- X-UEA-Spam-Flag: NO X-checked-clean: by exiscan on noralf X-UiB-SpamFlag: NO UIB: -13.8 hits, 8.0 required X-UiB-SpamReport: spamassassin found; -15 From is listed in 'whitelist_SA' 0.1 BODY: Message is 30% to 40% HTML 0.0 BODY: HTML included in message 1.1 BODY: Message only has text/html MIME parts Eystein John sent these remarks - have not talked with him yet - but not sure what is now required Keith X-IronPort-AV: i="4.08,132,1154908800"; d="scan'208,217"; a="17827006:sNHT58118592" Subject: Chpt 6 - last 1000 yrs Date: Wed, 16 Aug 2006 16:14:52 +0100 X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: Chpt 6 - last 1000 yrs Thread-Index: AcbBRrj0FPNJH9bQTyCswuNw7Ln3bw== From: "Mitchell, John FB \(Chief Scientist\)" To: "Keith Briffa" Cc: "Mitchell, John FB \(Chief Scientist\)" X-UEA-Spam-Score: 2.1 X-UEA-Spam-Level: ++ X-UEA-Spam-Flag: NO Hi Keith I have tried to cindense what I think the main issues for the and what the response is below. The weakest area seems to be statistical significance and by implication the likely/ very likely statements. I can't think of any easy solution - in the TAR for detection and attribution we used 95% limits on stats tests and them downrated them to allow for other uncertainties. I am interested in your comments John Issues 1. Reliance on Bristlecone pine - Response - the issues are in calibration period- they agree with other indicators for the rest of the record 2. Centring of principle components leads to "hockeysticks"- Response - this makes only a small difference when standardised data used. Comment - Would be useful to know which reconstructions do and donot make this assumption- this could strengthen the response 3. The divergence issue- Response - it is only apparent in high latitudes, and only with some trees. Comment- Do we know what happens if we eliminate those records with a divergence problem. The wider issue is whether or not it is reasonable to extend the reconstructions outside the calibration range. 4. There are different ways of verifying reconstructions and assigning significance levels( calibration period or seprate verifying period, different statistics) Response ? Comment- it is difficult in the text to gauge how well reconstructions are validated - eg using the calibration period to estimate errors as opposed to an independent period clearly makes a difference. This is important where "likely", "very likely"are used- based on what statistics? I think this is the area where I think the current response is weakest 5. Robustness- Burger and Cubasch show a wide range of results using different assumptions- Response ? Mann makes a reasoned defence- there are other checks and tests which would rule out many of the arbitrary assumptions explored by Cubasch and Burger, but this is not clear in the response to M&M etc -- Professor Keith Briffa, Climatic Research Unit University of East Anglia Norwich, NR4 7TJ, U.K. Phone: +44-1603-593909 Fax: +44-1603-507784 http://www.cru.uea.ac.uk/cru/people/briffa/ -- ______________________________________________________________ Eystein Jansen Professor/Director Bjerknes Centre for Climate Research and Dep. of Earth Science, Univ. of Bergen Allégaten 55 N-5007 Bergen NORWAY e-mail: eystein.jansen@geo.uib.no Phone: +47-55-583491 - Home: +47-55-910661 Fax: +47-55-584330