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Changes
SW: →Tropical troposphere: Added RC citation
However, one of the two satellite-based tropospheric estimates (RSS) shows a trend of 0.18°C per decade. [AR4 Fig. 3.18] Moreover, as acknowledged in the ISPM, models predict amplified warming in the tropical '''upper troposphere''', not the tropical troposphere as a whole. [ISPM 2.1c, AR4 10.3.4] There are no estimates for temperature trends in the upper troposphere in the data sets found in AR4.
Moreover, models predict higher temperatures in the upper tropical troposphere with long-term warming, no matter whether the forcing is anthropogenic (greenhouse gases) or natural (solar) [http://www.realclimate.org/index.php/archives/2007/12/tropical-troposphere-trends/#more-509]. As noted in the section below, it is the combination of tropospheric warming and startospheric cooling that most clearly distinguishes greenhouse gas induced warming from natural external forcings.
The ISPM goes on: "One of the available satellite data sets shows trends consistent with increased warming at higher altitude in the tropics ... '''while others do not'''." [ISPM 2.1c]
However the IPCC states: "After 1987, when MSU channel 3 became available, Fu and Johanson (2005), using RSS data, found a systematic trend of increasing temperature with altitude throughout the tropics." [AR4 3.4.1.2.2] This is the only satellite data based study cited in AR4 that addresses the issue at all.
The ISPM also states: "Adjusting T2 data to remove an estimated contribution from the stratosphere yields tropospheric trend coefficients ranging from about 0.12 oC to 0.19 oC per decade, '''depending on the method.'''" [ISPM 2.1c] In fact, the method employed makes little difference. The difference between UAH and RSS results is almost entirely due to the different T2 data filtering and adjustments '''prior''' to adjustments to remove spurious stratospheric cooling, as seen in a comparison of the "Troposphere" (RSS stratospheric removal method) and "Lower troposphere" (UAH removal method) panels. [AR4 Fig. 3.18] For example, RSS adjusted trend is 0.19 if the RSS method is employed, and 0.18 if the UAH method is employed.