"The expected 'hotspot' in the troposphere is missing"

This is a very technical argument, but it has been adequately debunked.  See http://scienceblogs.com/illconsidered/2009/08/the_missing_hotspot_misses_the.php?utm_source=sbhomepage&utm_medium=link&utm_content=channellink.

In short, the "hotspot" is not a predicted fingerprint of warming due to increased GHGs. It is predicted to exist regardless of any warming or any cause of such warming.  So its absence did suggest the models are not perfect, but it did not point suspicion away from GHGs. 

Recently it has been shown that the measurements were unreliable, and the hotspot has now been found.  See also http://www.csiro.au/news/Are-Climate-Models-Inconsistent--ci_pageNo-2.html.

Meanwhile, there is a fingerprint predicted for GHG-induced warming: as the blanket of GHGs holds in more heat in the lower levels of the atmosphere, the stratosphere above cools and shrinks (leading to the darkly humorous remark that the sky really is falling!)  That would not be expected if, for example, the cause were extra output from the sun.  Yet cooling in the stratosphere is indeed what we see.