Tropospheric temperature change since 1979 from tropical radiosonde and satellite measurements

Abstract

[1] Temperature change of the lower troposphere (LT) in the tropics (20°S-20°N) during the period 1979-2004 is examined using 58 radiosonde (sonde) stations and the microwave-based satellite data sets of the University of Alabama in Huntsville (UAH v5.2) and Remote Sensing Systems (RSS v2.1). At the 29 stations that make both day and night observations, the average nighttime trend (+0.12 K decade À1 ) is 0.05 K decade À1 more positive than that for the daytime (+0.07 K decade À1 ) in the unadjusted observations, an unlikely physical possibility indicating adjustments are needed. At the 58 sites the UAH data indicate a trend of +0.08 K decade À1 , the RSS data, +0.15. When the largest discontinuities in the sondes are detected and removed through comparison with UAH data, the trend of day and night releases combined becomes +0.09, and using RSS data, +0.12. Relative to several data sets, the RSS data show a warming shift, broadly occurring in 1992, of between +0.07 K and +0.13 K. Because the shift occurs at the time NOAA-12 readings began to be merged into the satellite data stream and large NOAA-11 adjustments were applied, the discrepancy appears to be due to bias adjustment procedures. Several comparisons are consistent with a 26-year trend and error estimate for the UAH LT product for the full tropics of +0.05 ± 0.07, which is very likely less than the tropical surface trend of +0.13 K decade À1.

Melting of major Glaciers in the western Himalayas: evidence of climatic changes from long term MSU derived tropospheric temperature trend (1979–2008)

“…For channel 2, it was consistent with two analyses (RSS, p=0.54, and the University of Maryland, p=0.32) but not with the University of Alabama dataset (p=0.0001) . The RSS MSU data, collocated from 58 radiosonde stations in the tropics (20 • S-20 • N) during the period of 1979-2004 show +0.15 • K/decade while the UAH processed data show +0.07 • K/decade (Christy et al, 2007). The comparison of the RSS-derived tropospheric temperature trend with four different observed estimates of surface temperature changes over the tropical troposphere show consistency with the model results (Santer et al, 2008).…”

What Do Observational Datasets Say about Modeled Tropospheric Temperature Trends since 1979?

“…One can argue that systematic biases still persist in the same way in all datasets, but for T LT , these are likely small in the aggregate [6]. A problematic issue impacts RAOBCORE and RICH and is related to a warming shift in 1991 of the upper troposphere in the ERA-40 Reanalyses on which the two datasets rely.…”

“…There have been essentially two groups of publications on this contentious issue, one reporting that trends of T LT in observations and models are statistically not inconsistent with each other (e.g., [4,5]) and the other reporting that model representations are significantly different than observations, thus pointing to the potential for fundamental problems with models (e.g., [2,[6][7][8][9][10].) With the new information noted above, we will look again into this controversy which primarily centers on the acceptance of a magnitude of the T LT trend.…”

Recent slowdown of tropical upper tropospheric warming associated with Pacific climate variability

“…The difference in the T TUT trends between the observations and models cannot be assessed easily because uncertainties in the T TUT trends based on the radiosonde and satellite observations and GCM simulations [Thorne et al, 2005;Sherwood et al, 2005;Randel and Wu, 2006;Christy et al, 2007;Haimberger et al, 2008;Allen and Sherwood, 2008] are large compared with the difference between them [Santer et al, 2008;Thorne et al, 2011;Seidel et al, 2012]. However, the latest observational data suggest that the models have systematic warming biases in recent (since the late 1990s) T TUT variation ( Figure S1; see section 3.1) [Fu et al, 2011, Figure 3;Lott et al, 2013, Figure 4].…”