cc: , John Kennedy , David Parker date: Thu May 29 14:22:58 2008 from: Phil Jones subject: Re: Sea water temperatures from the Honourable Company of Master to: "Pdo" Phil, I'm cc'ing my brief answer to two people at the Met Office, in case they want to add anything. It is good to hear from people who have taken the sorts of observations we use! As you'll be aware there is a lot more to the issue than we were able to say in the Nature article (and in their own News and Views piece). The real problem with all the marine data is that before about 1970 we do not know how individual ships measured SST (buckets or intakes - and the different variants of both). So we've had to make assumptions about which fleets (maritime and naval) used which types of buckets and which types of intake measurements and hull sensors. The number of observations per 'square' of the ocean does beat down the noise associated with individual readings. There are parts of the oceans where this doesn't (the Southern Oceans for example) and periods (the two WWs). In the two WW periods there are markedly fewer observations from fewer fleets and countries. We have a naval historian selecting British log books for additional digitization for the two WW periods and the few years either side as well as the nineteenth century. There are many more British log books than any other nation and we've only digitized a small percentage of them Effort is being focussed on areas and periods where overall the number of observations are fewest. The situation will improve but digitizing isn't cheap and takes time. The number of observations will improve, but I don't think this will change the big picture. There is the issue recently when the number of ships taking obs has reduced, partly due to commercial considerations. We have a lot more automated observations now from drifters and buoys, but these need replacement every few years. If you can help in any way to slow down or stop the decline in commercial ships taking weather observations then I'm sure David Parker can put you in touch with people in Southampton. Thanks for your interest in the paper. Phil At 11:30 29/05/2008, Pdo wrote: Dear Professor Jones I have just read with great interest the reporting of your work on sea water temperatures. However, am a little confused by what has been reported. Firstly the canvas bucket v sea water intake differences. We were always taught by the met office that only surface temperatures should be taken using the bucket just dipped into the sea. The design of the bucket greatly reduced colling through evaporation as it was double skinned. The sea water intake is by definition below the waterline. This must remain below the waterline at all stages of loading. So if you take a ship with a lightship draught of 2m its sea water intake will be just below the surface. If you now load that ship, the intake is now some 10m below the surface. This must throw up an enormous variation in readings. Secondly, the UK register after 1945 greatly increased to its heyday in the 1970s before declining again. During this time the number of reports from UK ships must have grown vastly, dwarfing the number of US sources. This must then through up some variation in temperature reading methods post say the mid 50s. Thirdly, as a former navigator I remember how hit and miss the whole method was. Chucking this bucket over the side, pulling it back in (trying not to hit the side of the ship and wake the Captain), peering at the thermometer with a weak torch in the middle of a gale, spilling most of the water, making up readings, copying what others had written before (as it was dark, blowing a hooley and you couldn't be bothered to go onto the bridge wing). And I was a pretty conscientious officer. The met reports from the observing ships is pretty dubious at times. I remember crossing the Atlantic one time and could not understand why there was this isolated fog bank following us across as indicated on the weather fax. Then checked the visibility codes for our reports and found that we had all just been copying the wrong number down. Would be interested to hear some thoughts about the above issues though. BR Phil ------------------------------------------------- Dr Phillip Belcher Professional Development Officer Honourable Company of Master Mariners HQS "Wellington" London WC2R 2PN Tel 020 7836 8179 Tel 029 2021 7699 E-mail pdo@hcmm.org.uk [1]www.hcmm.org.uk Sea's the Future [2]www.worldmaritimeday.com ___________________________________________________________________________________ Disclaimer This message (including any attachments) are confidential and may be legally privileged. If you are not the intended recipient you should not disclose, copy or use any part of it - please delete all copies immediately and reply that you have received this misdirected email. The company accepts no responsibility for changes to this message after it was sent nor any loss or damage arising from its receipt or use. The company reserves the right to monitor e-mails and any replies, also all statements expressed in this email are personal to the sender and do not necessarily represent the opinions or policies of the company. 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 ----------------------------------------------------------------------------