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Which is the Most Accurate Satellite-Derived Temperature Dataset?

Paper Reviewed
Christy, J.R., Spencer, R.W., Braswell, W.D. and Junod, R. 2018. Examination of space-based bulk atmospheric temperatures used in climate research. International Journal of Remote Sensing 39: 3580-3607.

Monitoring temperature and creating regional and global temperature data sets is a tricky business. There are many factors that can induce spurious trends in the data; and there are multiple protocols to follow to ensure their proper construction. Consequently, many people (including scientists) have found themselves wondering which of all the temperature data sets is the most accurate for use in determining the impact of rising greenhouses gases on atmospheric temperature? Thanks to the recently published work of Christy et al. (2018), we now have a pretty good idea as to the answer.

As their contribution to this topic, the four scientists from the Earth System Science Center at the University of Alabama (Huntsvile, AL) analyzed mid-tropospheric temperatures derived from microwave sounding units from four satellite datasets: University of Alabama (UAHv6.0), Remote Sensing Systems (RSSv4.0), NOAAv4.0 and University of Washington (UWv1.0). These datasets provide monthly gridded mid-tropospheric temperature anomalies on a near-global 2.5 x 2.5 degree grid (85°S-85°N, except for UWv1.0 that is 30°S-30°N only) over the period 1979-2016.

After completing a series of analyses and comparisons of the satellite data with several independent mid-tropospheric temperature datasets (radiosonde/balloon and Reanalyses), Christy et al. concluded that there is "substantial evidence to support the hypothesis that the satellite datasets experienced spurious warming during the period that began with [the] NOAA-12 [satellite] and ended with NOAA-14 (1990-2001+)," noting that "the impact is least obvious in UAH data and most in UW."

With respect to the significance of their findings, the researchers note that the temperature trend of the tropical mid-troposphere (20°S-20°N) is assumed to be a key indicator or fingerprint of the response of the climate system to greenhouse gas forcing, such that rising greenhouse gases are expected to have increased temperatures there by 0.27°C decade-1 since 1979 (based on an average of 102 climate model simulations). However, Christy et al. report that this model-based estimate is not correct, as they calculate the actual trend to be a much smaller 0.10°C decade-1.

These data-driven observations indicate that the recent warming rate of the tropical mid-troposphere is more than a factor of two smaller than what global warming theorists contend it should be, which findings reveal that the earth-atmospheric-ocean system is likely a lot less sensitive to rising atmospheric CO2 than what climate alarmists would have us believe. And that lack of temperature sensitivity drives a stake into the heart of all of their ancillary climate scare scenarios that are dependent on a higher rate of warming to occur, include future scenarios of melting polar ice caps, accelerating sea level rise, more frequent and more severe extreme weather events, etc. No wonder the alarmists have gone to great lengths to discredit the UAH satellite data set, going so far as to create versions of their own, versions that Chirsty et al. have now meticulously shown to be contaminated with spurious warming.

Posted 6 April 2018