A very interesting remark by Roy Spencer in a guest blog at Roger Pielke Sr’s:
[…] Oscillation, or any other mode of internal variability will ALWAYS look like positive feedback – even if there is no feedback present. The question of how the neglect of this effect has contaminated observational estimates of feedback has never even been addressed, let alone answered.
I repeat: to the extent that any non-feedback radiative fluctuations occur, their signature in climate data LOOKS LIKE positive feedback. And when modelers use those relationships to help formulate cloud parameterizations, it can lead to models that are too sensitive. […]
Obviously the above does not mean there is _no_ positive feedback. It “just” means that this “fake feedback” effect has to be removed from the data BEFORE announcing to the world how sensitive climate is eg to CO2 concentrations.