Reconciling Observations of Global Temperature Change (2000) / Chapter Skim
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7 MSU Observations
7 MSU Observations
Pages 41-49
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From page 41... ...
Each day, the MSU observes approximately 80% of the earth's surface, with the orbit shifting slightly each day so that 100% coverage is achieved over a three to four day period. To date, nine MSUs have been used operationally, forming an uninterrupted daily time series from 1979 to the present.
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From page 42... ...
MSU TEMPERATURE TRENDS The geographical distribution of MSU lower to mid-tropospheric temperature trends is shown in Figure 7.~. it is evident that the regions of rapid surface warming apparent in Figure 6.2 (e.g., Western Europe, Eastern Russia)
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From page 43... ...
warming events in 1983, 1987, 1991, and 1997; the cooling events in 1985, 198S, 1996, and 1999; and the volcanic aerosol cooling events in 1982 and 1991 (Christy and McNider, 1994~. Over the past 20 years, MSU observations indicate that the globally averaged lower to mid-tropospheric temperature has increased at a rate of approximately 0.05 °C/decade, as computed using the ordinary least squares statistical method.
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From page 44... ...
SOURCES OF UNCERTAINTY IN TREND ESTIMATES As with all climate data sets, there are drawbacks and limitations associated with the MSU temperatures. To begin with, MSU channels 2 and 4, as well as products derived directly from these channels, have quite coarse vertical resolution.
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From page 45... ...
Aside from the issue related to the method chosen for merging the satellite data, there is also an uncertainty associated with determining each satellite's bias relative to some reference value. Several tests have been performed in which the biases were calculated from separate subsections of the overlapping periods, demonstrating very high
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From page 46... ...
Fortunately, this effect can be precisely modeled using the satellite orbital data and a relatively simple radiative transfer model. However, it is worth noting that this particular effect, known as orbit decay, was not recognized until quite recently (Wentz and Schabel, 1998)
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From page 47... ...
(3) Using two different global radiosonde data sets, error estimates were derived.
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From page 48... ...
from 1979 to 1998. To highlight the differences between the curves, the vertical scale has been expanded by 50% relative to the report's other MSU time series figures.
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From page 49... ...
MSU Observations 49 Others, however, view this analysis as not rigorous enough to reliably identify measurement error at the precision required for decadal-scale climate monitoring, and estimate the measurement error in the MSU trend to be about +0.! °C/decade (Hurrell and Trenberth, 1998)
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