There is also an important issue of SST trends. Jim Hurrell and Kevin Trenberth in their 1999 paper suggested that the analysis which conservatively assumes the stationarity of the mean SST climatology (like ours) might be underestimating the long-term changes in the SST, and argued that it is better to figure out the long-term variability beforehand and prescribe it a priori (e.g. like it is done in the HadISST1). Their criticism regarding long-term trend underestimation is certainly valid, as our preliminary study has shown; however, prescribing the global trend a priori might result in overestimation of it by the analysis — not a good outcome either (Kaplan et al. 2001).

Looks like a topic for another time.

Kaplan offers a cool/neat/hip/awesome plotter, located here , for a sample month. Simply plug in a latitude and longitude box and date, then hit plot. The result is a map of ship SST observation densities (# of observations per month in a 5 degree by 5 degree box).

An example for the tropical Atlantic is below. The red box is the MDR:

Other samples for September are below:

Note the lack of SST observations (and probably weather observations in general) in 1945.

That’s a pretty significant difference between the two. If I’d used Kaplan instead of Smith-Reynolds I’d get a 1950s peak pretty close to the 2000s peak.

Which is more appropriate for tropical Atlantic SST? I don’t know but I’d sure like to see the detailed derivation of the SST differences for random example years, say 1970, 1985 and 2000, just so I could understand the mechanics of the derivations.

and a modified plot, incorporating a warming of +0.3C in 1945 which linearly declines to zero by 1980:

(Carl, by the way, I hope you don’t mind me naming the adjustment after you. I think you’re the reader mentioned by Steve M. in the earlier SST post.)

This adjustment improved the correlation ( r ) between Atlantic PDI and SST from 0.50 to 0.52 Not much of an impact.

Another thing to note when looking at model hindcasts is to note that
they arent very skillful at modeling “non volcanic” cooling periods.

That’s probably a comment for a different thread.

Kenneth or Bob K, if you have time and want to incorporate the possible adjustments into MDR and other tropical Atlantic SST subsets to see what they look like, that’d be great for people at CA to see.

David, since I have convinced myself, for the time being at least, that when the TC/hurricane count and ACE index for the NATL long time series are adjusted for detection capability changes and cyclical components, like AMM, the trends that could be attributed to SST changes are not evident, I do not have much motivation to look at SST corrections — unless it turns out that the SST has been flat over the long term.

I am interested in what the “adjusted” SSTs would look like. I have a link below that has a breakpoint for the global mean temperature (GMT)around 1945 and I believe various methods of measuring breakpoints show one at that approximate time. These breakpoints have been discussed here at CA previously with constant reminders from Steven Mosher. Breakpoints are seen additionally near 1900 and 1980 for the GMT.

http://ams.confex.com/ams/pdfpapers/100694.pdf