Reducing Noise in the MSU Daily Lower-Tropospheric Global Temperature Dataset

John R. Christy University of Alabama in Huntsville, Huntsville, Alabama

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Roy W. Spencer NASA/Marshall Space Flight Center, Huntsville, Alabama

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Richard T. McNider University of Alabama in Huntsville, Huntsville, Alabama

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Abstract

The daily global-mean values of the lower-tropospheric temperature determined from microwave emissions measured by satellites are examined in terms of their signal, noise, and signal-to-noise ratio. Daily and 30-day average noise estimates are reduced by almost 50% and 35%, respectively, by analysing and adjusting (if necessary) for errors due to 1) missing data, 2) residual harmonics of the annual cycle unique to particular satellites, 3) lack of filtering, and 4) spurious trends. After adjustments, the decadal trend of the lower-tropospheric global temperature from January 1979 through February 1994 becomes −0.058°C, or about 0.03°C per decade cooler than previously calculated.

Abstract

The daily global-mean values of the lower-tropospheric temperature determined from microwave emissions measured by satellites are examined in terms of their signal, noise, and signal-to-noise ratio. Daily and 30-day average noise estimates are reduced by almost 50% and 35%, respectively, by analysing and adjusting (if necessary) for errors due to 1) missing data, 2) residual harmonics of the annual cycle unique to particular satellites, 3) lack of filtering, and 4) spurious trends. After adjustments, the decadal trend of the lower-tropospheric global temperature from January 1979 through February 1994 becomes −0.058°C, or about 0.03°C per decade cooler than previously calculated.

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