NOT SO GREEN  |  Drift & Grift

By steven d keeler | Jul 07, 2017
Source: UAH


Our UAH globally-averaged trend is now about + 0.12 C/decade, while the new RSS trend has increased to about + 0.17 C/decade.

Note these trends are still well below the average climate model trend for LT, which is + 0.27 C/decade.

These are the important numbers; the original Carbon Brief article headline ( “Major correction to satellite data shows 140% faster warming since 1998” ) is seriously misleading, because the warming in the RSS LT data post-1998 was near-zero anyway ( 140% more than a very small number is still a very small number ).

Since RSS’s new MT dataset showed more warming that the old, it made sense that the new LT dataset would show more warming, too. Both depend on the same instrument channel ( MSU channel 2 and AMSU channel 5 ), and to the extent that the new diurnal drift corrections RSS came up with caused more warming in MT, the adjustments should be even larger in LT, since the diurnal cycle becomes stronger as you approach the surface ( at least over land ).




Background on Diurnal Drift Adjustments

All of the satellites carrying the MSU and AMSU instruments ( except Aqua, Metop-A and Metop-B ) do not have onboard propulsion, and so their orbits decay over the years due to very weak atmospheric drag. The satellites slowly fall, and their orbits are then no longer sun-synchronous ( same local observation time every day ) as intended. Some of the NOAA satellites were purposely injected into orbits that would drift one way in local observation time before orbit decay took over and made them drift in the other direction; this provided several years with essentially no net drift in the local observation time.




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