Sigh. I have the distinct recollection that we've been through all of this before. That bell curve on the left is the weighting function, you doofus.
Radiosondes agree with me. Here - I'll prove it. I went to https://www1.ncdc.noaa.gov/pub/data/ratpac/ratpac-a/ to download the annual data for RATPAC-A. Then I separately took the tropics (20S-20N and 30S-30N) and extratropics (NH and SH) and calculated the temperature trend for each pressure level. The result looks like this:
Blue and orange are the tropics, grey and yellow are the northern and southern extratropics respectively. Exactly as I've been saying, the switch from warming to cooling (the place where the trend crosses zero) is at a much higher altitude in the tropics (~150 mbar - about 14 km) compared to higher latitudes (~250 mbar - about 11 km).
For completeness' sake, here's the temperature trends for the 70, 50 and 30 mbar levels for the tropics:
the northern extratropics:
... and the southern extratropics:
If you can't see cooling trends there, then there's nothing more I can do for you.
