Idag hittade jag ett mycket intressant inlägg på Dr Roy Spencers blogg. Det handlar om havstemperatur med anledning av den senaste tiden El Nino-relaterad värme.
För enkelhetens skull återger jag hela inlägget nedan. Dessvärre går det inte att kommentera på Roy Spencers blogg, så vi kanske kan ha en liten diskussion här i stället.
Something’s Fishy With Global Ocean Temperature Measurements
Yesterday I posted the satellite-based global-average monthly sea surface temperature (SST) variations since mid-2002, which was when the NASA Aqua satellite was launched carrying the Advanced Microwave Scanning Radiometer for EOS (AMSR-E). The AMSR-E instrument (which I serve as the U.S. Science Team Leader for) provides nearly all-weather SST measurements.
The plot I showed yesterday agreed with the NOAA announcement that July 2009 was unusually warm…NOAA claims it was even a new record for July based upon their 100+ year record of global SSTs.
But I didn’t know just HOW warm, since our satellite data extend back to only 2002. So, I decided to download the NOAA SST data from their website — which do NOT include the AMSR-E measurements — to do a more quantitative comparison. (The NOAA oceanic data they post there seem to be based upon the UK Climatic Research Unit [CRU] data, but I could not tell whether those are indeed the data that were the basis for NOAA’s record high temperature announcement).
From the NOAA data, I computed monthly anomalies in exactly the same manner I computed them with the AMSR-E data, that is, relative to the June 2002 through July 2009 period of record. The results (shown below) were so surprising, I had to go to my office this Saturday morning to make sure I didn’t make a mistake in my processing of the AMSR-E data.
As can be seen, the satellite-based temperatures have been steadily rising relative to the conventional SST measurements, with a total linear increase of 0.15 deg C over the 7 year period of record versus the conventional SST measurements.
If the satellite data are correct, then this means that the July 2009 SSTs reached a considerably higher record temperature than NOAA has claimed. The discrepancy is huge in terms of climate measurements; the trend in the difference between the two datasets shown in the above figure is the same size as the anthropogenic global warming signal expected by the IPCC.
I have no idea what is going on here. Frank Wentz and Chelle Gentemann at Remote Sensing Systems have been very careful about tracking the accuracy of the AMSR-E SST retrievals with millions of buoy measurements. I checked their daily statistics they post at their website and I don’t see anything like what is shown in the above figure.
Is it possible that the widely-used CRUT SST temperature dataset has been understating recent warming? I don’t know…I’m mystified. Maybe Frank, Chelle, Phil Jones, or some enterprising blogger out there can figure this one out….I’ve got to go hang some plywood.