SCIENTISTS at the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center (CPC) appear to have made a blunder with a data adjustment and splice resulting in sea surface temperatures being warmer than they would otherwise be by about 0.175 degrees C over the last two decades.
Roy Spencer, from the University of Alabama, discovered the error just a few days ago which according to meteorologist Anthony Watts, accounts for 24% of the 0.74 deg C global warming claimed for 1905-2005.
UPDATE: THE ERROR WAS ROY SPENCERS
To make a long story short, because the orbit boost caused the TMI to be able to “see” to slightly higher latitudes, the way in which individual latitude bands are handled has a significant impact on the resulting temperature anomalies that are computed over time.
The previous results I presented were for the 40N to 40S latitude band, which is nominally what the TMI instrument sees today. But before 2001, the latitudinal extent was slightly smaller than it was after 2001.
If I restrict the latitude range to 38N to 38S, which was always covered during the entire TRMM mission, I find that the divergence between the TMI and NOAA average SST measurements essentially disappears.
Even though I was processing the NOAA and TMI datasets in the same manner, I should NOT have been. This is because there were not as many gridpoints over cooler SST regions going into the ‘global’ averages before the satellite altitude boost as after the boost. So, for example, one must be very careful in computing a latitude band average, say from 39N to 40N, to make sure that there has been no long-term change in the sampling of that band.
Based upon the above comparisons, I would now say there is no statistically significant difference in the SST trends since 1998 between TMI, the NOAA ERSSTv3b product, and the HadSST2 product. And it does look like July 2009 might well have experienced a warmer SST anomaly than July 1998, as was originally claimed by NOAA. (Remember, TMI can not see all of the global oceans, just equatorward of about 40 deg. N and S latitude.)
September 2, 2009
The mistake was made about 10 years ago following a request from the World Meteorological Organization for NOAA to standardize the period from which temperature anomalies are calculated.
I have puzzled as to why Australian government advisors claim sea temperatures have been increasing over the last ten years – perhaps they have been referring to sea surface temperatures and focusing on this dud data.
Of course NASA started deploying free floating Argo buoys in the world’s oceans in 2000 with the full complement of 3,000 in place by 2003, and measurements from these well spread buoys indicates that the oceans have been cooling since 2003.
People make mistakes. In this case the mistake got through peer-review.
Given the many mistakes made by those compiling, adjusting and averaging global temperature data including sea surface temperatures, it would perhaps be worth having one or a few reference sites against which all the adjusting and averaging could be compared. As carbon dioxide concentrations are often reported only for Mauna Loa, Hawaii, why not also discuss what is happening here when discussing global warming and sea surface temperatures.
Notes and Links
The above graph shows the likely magnitude of the error made by NOAA with it most pronounced since 2001, more information at http://www.drroyspencer.com/2009/08/spurious-warming-in-new-noaa-ocean-temperature-product-the-smoking-gun/ and http://wattsupwiththat.com/2009/08/27/spencer-noaa%E2%80%99s-official-sea-surface-temperature-product-ersst-has-spurous-warming/
Interdecadal Changes of 30-Yr SST Normals during 1871–2000
YAN XUE, NOAA/NWS/NCEP Climate Prediction Center, Camp Springs, Maryland
THOMAS M. SMITH AND RICHARD W. REYNOLDS, NOAA/NESDIS National Climatic Data Center, Asheville, North Carolina
J O U R N A L O F C L I M A T E, VOLUME 16
Part 1 of ‘Let’s Stop Averaging Global Temperatures’ is here: http://jennifermarohasy.com/blog/2009/08/stop-averaging-global-temperatures-part-1/