Carl Mears and team at RSS have published a new paper describing a revision of their data for atmospheric temperature. The focus is on improving the “diurnal correction,” which is necessary because different regions of Earth are observed at different times of day. The upshot is that the lower atmosphere has warmed faster than was previously believed.
Perhaps the abstract says it best:
Temperature sounding microwave radiometers flown on polar-orbiting weather satellites provide a long-term, global-scale record of upper-atmosphere temperatures, beginning in late 1978 and continuing to the present. The focus of this paper is the middle tropospheric measurements made by the Microwave Sounding Unit (MSU) channel 2, and the Advanced Microwave Sounding Unit (AMSU) channel 5. Previous versions of the RSS dataset have used a diurnal climatology derived from general circulation model output to remove the effects of drifting local measurement time. In this paper, we present evidence that this previous method is not sufficiently accurate, and present several alternative methods to optimize these adjustments using information from the satellite measurements themselves. These are used to construct a number of candidate climate data records using measurements from 15 MSU and AMSU satellites. The new methods result in improved agreement between measurements made by different satellites at the same time. We choose a method based on an optimized second harmonic adjustment to produce a new version of the RSS dataset, Version 4.0. The new dataset shows substantially increased global-scale warming relative to the previous version of the dataset, particularly after 1998. The new dataset shows more warming than most other middle tropospheric data records constructed from the same set of satellites. We also show that the new dataset is consistent with long-term changes in total column water vapor over the tropical oceans, lending support to its long-term accuracy.
The effect on TMT (middle-troposphere temperature) globally looks like this:
The black line shows the old version, the light blue line the new. Note that the overall trend in the new version is 60% bigger than in the old version. The green line at the top shows the effect of their improved diurnal correction.
This should dampen the enthusiasm of deniers like Ted Cruz who have relied on satellite data from RSS to dispute global warming. But I doubt; I suspect instead that Ted Cruz will either find some new reason to deny global warming, or will go on a witch-hunt of Carl Mears and the RSS team, accusing them of fraud because the data don’t say what Ted Cruz and his ilk want it to say.
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