First Look at April Temps: GISS not yet reported
Posted by The Diatribe Guy on May 7, 2008
The temperature index data is starting to come out for April month end.
Starting with This raw data, the RSS MSU LT measure we get an anomaly of 0.080 (or, in units equivalent to GISS, a value of 8.0).
The anomaly isn’t necessarily comparative to GISS or other measures because it depends on the baseline. What’s more important is the movements. From the linked file, the last year+ looks like this:
Also, the UAH anomaly data has been released and can be found here. Since both this measure and the RSS data are satellite measures, they are only in existence since 1978, as compared to GISS and HadCrut data, which are surface measures. However, they are also subject to far fewer adjustment algorithms. They are fairly consistent with one another, keeping in mind that 1 = .01 degrees Celsius anomaly.
The NOAA (NCDC) anomalies have not yet been released yet, either. These are surface temperatures, and can be found here. For curiosity’s sake, here are how those anomalies compare through March, though. The baseline is different, so the point of comparison is the difference in values from period to period, not actual magnitude of the anomaly.
Of interest to me is the this article, which tells us that NCDC admits that their temp measurement is substandard, but presents their plan for improving it. One of the great benefits will be that there will no longer be these adjustments to past data that continues to change the temperature anomalies going back a century. This is a criticism of NCDC as well as GISS.
The GISS data (I started using the global Land + Sea Surface table) has not yet been released. But it is interesting to see how that compares to the above readings. The baseline is different, so the anomalies are higher, so again it’s more interesting to look at how the numbers compare relative to previous readings. The GISS table is here.
Last month, GISS had the March anomaly as the highest reading since January 2007, while the satellite measures had the anomaly significantly lower than any readings in the first 9 months of the previous year. GISS uses a colder base period, so the numbers are higher, but the difference in the anomalies should be fairly consistent.
Right now, my anomaly forecast model uses the GISS data, so I’m waiting to see how that turns out. Based on months previous to March (from January 2007 through February 2008), the difference between the satellite data ranged from a low of 14.7 to a high of 36.9 against RSS. The difference was between a low of 16.6 and a high of 39.6 against the UAH data. Historically, the average I’ve heard is about 26, and this seems to fit in with the ranges above as well as the average over that time period of 26.1 against RSS and 27.6 against the UAH data.
That is the reason that Hansen and GISS skeptics nearly choked on their spittle last month when the March anomaly of 67 was released. That is a whopping difference of 55.1 against RSS and 54.1 against UAH. Now, I have not run the differences back to 1978 or anything to see how rare of an occurrence a difference of this magnitude is. Perhaps I’ll look at that. But it certainly was an unexpectedly high differential, and was fodder for those who simply distrust Hansen’s motivations at NASA. I’ve previously outlined the substantial historical revisions to the GISS data and their impact on the trend line, which has exacerbated the warming trend line. Just more fuel for the fire. I have not heard a good explanation for the difference.
That all said, it would seem that if March is just an “anomaly,” then the expected value of GISS will be in the area of 28 to 34, on average, with a potentially reasonable low value of 22 and a reasonable high value of 44. But we shall see.
To be fair to Hansen, the NOAA data also mirrored the NASA anomaly. So it could have just been some strange month where, for whatever reason, the satellite measurements just deviated from surface station measurements. It will be interesting to see if the NOAA data starts to deviate from GISS in the future once the station enhancements are made.