From	Phil Jones	Date	Mon Oct 5 12:35:37 2009
To	Tom Wigley
CC	Ben Santer
Subject	Re: NCDC data
Tom, I can't see why the data become ERSSTv3b. b seems all that you can download. I reviewed the 2008 paper. The version that I reviewed had something in for the problem of SST data now re drifters and ships, but they pulled that section. I recall saying it needed to be watertight and they needed to explain the spatial pattern to the ship minus drifter field. Maybe that version was a? I was never that keen on their infilling. It biases the values before the 1920s when you infill with anomalies that are nearer to zero. You can see this in their Fig6. This version is better than their previous one. I always assumed they still had gaps - as it would be impossible to infill the Antarctic and some parts of the Southern Oceans. Have you tried looking at their Antarctic average - 65-90S for example? Their globe should be one domain, so not (NH+SH)/2 but for an infilled dataset this shouldn't make any difference. I wonder if they downweight the infilled values in some way? They have their error field? The 2008 paper doesn't say how they compute Global and NH and SH. Are NH and SH the same as you get? Cheers Phil At 06:56 05/10/2009, Tom Wigley wrote: Phil, Ben, Have you looked at the latest NCDC global data? It seems odd. The data on their site is ERSSTv3 (Smith et al. 2008). As far as I know, this is an infilled data set with no gaps. As such, (NH+SH)/2 should be the same as their global mean. For monthly data, this is not the case. There are actually some big differences, even recently. Any idea why? Tom. 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 ----------------------------------------------------------------------------