cc: "David Pugh" , "Phil Jones" , "Kennedy, John" date: Thu, 11 Jun 2009 10:49:57 +0100 from: "Parker, David" subject: RE: SST bias advice to: "Philip Woodworth" Philip For bucket corrections, see Fig. 18 of the attached paper (Folland and Parker, 1995). In June 1860 near the Falklands (upper left panel), the estimated correction is less than 0.1 deg C. An underlying assumption is that about 75% of buckets were wooden at that time (Section 8d on page 351). However the instrumentation is likely to have varied from ship to ship, and unless we know what was done on board the Erebus, we cannot be absolutely sure of the bias. The Folland and Parker (1995) corrections are relative to a modern (1951-1980) mix of in situ SST data from engine intakes, insulated and uninsulated buckets and hull sensors. Corrections relative to the 1961-1990 reference period we now use will be very similar, but Thompson et al (2008)* have now pointed out the need for corrections to modern data. As AVHRR data are calibrated using buoys, and buoys appear to be biased slightly cold compared to ships (consult John Kennedy for more details), then the AVHRR may be biased cold, by an amount approaching 0.1 deg C, fortuitously yielding next-to-no bias relative to wooden buckets in Falklands winter! * Thompson D.W.J., Kennedy, J.J., Wallace J.M., Jones, P.D. 2008: A large discontinuity in the mid-twentieth century in observed global-mean surface temperature. Nature, 453, 646-649 doi:10.1038/nature06982. Regarding the contents of ICOADS, see http://icoads.noaa.gov/ and/or contact Scott Woodruff. I hope this helps, Regards David David Parker, Climate Research scientist Met Office Hadley Centre FitzRoy Road Exeter Devon EX1 3PB United Kingdom Tel: +44 (0)1392 886649 Fax: +44 (0)1392 885681 Email: david.parker@metoffice.gov.uk Website: www.metoffice.gov.uk See our guide to climate change at http://www.metoffice.gov.uk/climatechange/guide/ -----Original Message----- From: Phil Jones [mailto:p.jones@uea.ac.uk] Sent: Thursday, June 11, 2009 9:34 AM To: Parker, David Cc: Philip Woodworth; David Pugh Subject: Fwd: SST bias advice Philip, Been away Tues/Wed. Sending this reply back via David Parker, in case he has some more thoughts. First I'm not sure how much SST data are in ICOADS (even the CLIWOC work as well) from obs taken while a ship is in port or at anchor. I'd presume they get included, but they would seem like pier obs, so may be flagged as such. When I say flagged, you'd only know by looking at the locations and noticing these don't change for a month! Presumably the SST obs were taken with a bucket, which in the 1840s would have been a wooden bucket. This bias from wooden buckets is smaller than with the later canvas buckets (1890s to 1940s). David can probably tell you what this would be for wooden buckets in the 1850s. My guess is that it would be quite small - any adjustment for it would be an increase of between 0 and 0.2deg C, probably near the lower end. I also think you're better off talking to David than Dick Reynolds. Cheers Phil >Date: Tue, 09 Jun 2009 08:48:04 +0100 >From: Philip Woodworth >User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.10) >Gecko/20050909 Red Hat/1.7.10-1.1.3.2 >X-Accept-Language: en-us, en >To: Phil Jones , David Pugh >Subject: SST bias advice >X-Null-Tag: caf7d41d5458c87a0a940973831edf98 >X-MailScanner-NERC-Information: Please contact the ISP for more information >X-MailScanner-NERC-ID: n597m2XU032119 >X-MailScanner-NERC: Found to be clean >X-MailScanner-NERC-SpamCheck: not spam (whitelisted), > SpamAssassin (not cached, score=-3.5, required 5, autolearn=not spam, > BAYES_00 -3.50) >X-MailScanner-NERC-From: plw@pol.ac.uk >X-Spam-Score: undef - message too big (size: 1794432, limit: 512000) >X-CanItPRO-Stream: UEA:f028 (inherits from UEA:default,base:default) >X-Canit-Stats-ID: Bayes signature not available >X-Scanned-By: CanIt (www . roaringpenguin . com) on 139.222.131.184 > > >Hi Phil, > >Have you any advice on the below? I sent this to Reynolds in NOAA >but I am not sure he is around still? Anyway, as you were a >co-author of the IPCC chapter I wondered if you might have some >idea. I think I mentioned previously our work in the Falklands: > > >I would be very grateful for advice on likely bias in a set of >historical sea surface temperature measurements compared to the >primarily AVHRR ones of today. I have read up a bit on this subject (the >appendix to the measurement chapter in the 4AR was very useful) but >still find it hard to grasp what the possible biases might be. > >We are making comparisons of sea level measured in the Falklands in 1842 >by James Clark Ross to those of today, and in part of that work we >compared Ross's 'mean temperature of the sea surface' (see attached tif >image of one page of his journal) with those from the 'sst.mnmean.nc' >file from the CDC for 1981 onwards which is based on your (Reynolds) >2002 work. > >The Ross temperature for southern winter 1842 is about the same as you >get for a similar time of year in the CDC file (about 4.1 deg C). But do >you have any feel for how they might be relatively biased and, if so, >have you a reference we could quote? I realise this is a bit of long >shot - there is no information in his book I have found explaining how >the temperature measurements were made or the time of day. > >Many thanks in advance for the advice. > >Phil Woodworth > >-- >This message (and any attachments) is for the recipient only. NERC >is subject to the Freedom of Information Act 2000 and the contents >of this email and any reply you make may be disclosed by NERC unless >it is exempt from release under the Act. Any material supplied to >NERC may be stored in an electronic records management system. > > > Prof. Phil Jones Climatic Research Unit Telephone +44 (0) 1603 592090 School of Environmental Sciences Fax +44 (0) 1603 507784 University of East Anglia Norwich Email p.jones@uea.ac.uk NR4 7TJ UK ------------------------------------------------------------------------ ---- Attachment Converted: "c:\eudora\attach\Folland&Parker_QJRMS_1995.pdf"