# GFDL - Geophysical Fluid Dynamics Laboratory

Some feedbacks in AR4 models, from Held and Shell 2012.  The three red columns on the right provide the traditional perspective:  the “Planck feedback”– the response to uniform warming of surface and troposphere with fixed specific humidity ($\lambda_T$), the lapse rate feedback at fixed specific humidity ($\lambda_L$), and the water vapor feedback ($\lambda_Q$).  The three blue columns on the left provide an alternative perspective — with the fixed relative humidity uniform warming feedback ($\tilde{\lambda}_T$), the fixed relative humidity lapse rate feedback, ($\tilde{\lambda}_L$), and the relative humidity feedback ($\tilde{\lambda}_H$).  The sum of the three terms, shown in the middle black column, is the same from either perspective.  Surface albedo and cloud feedbacks are omitted. Each model is a dot.