Came across this study recently, in my view it is one of the strongest pieces of evidence supporting human caused climate change.
The authors document measurements of increasing re-radiated longwave radiation back down to the surface corresponding to the exact wavelengths you would expect to see for increasing carbon dioxide. This forcing of 0.2 w/m^2 per decade far exceeds any other natural forcing, especially since solar activity was continuing to decline from 2000-2011. The sun was providing a very weak negative forcing
which is inconsistent with the positive energy imbalance we've seen during that time.

This study is consistent with
Harries et al. 2001, and
Philipona et al. 2004, but is more recent, and in my view visualizes this increase in greenhouse forcing well.