It would be relatively simple to accurately define a "earth heat index" on a planetary scale.
A few orbiting satellites having the correct sensors could provide a true picture of energy in vs. energy out. Over a period of time, this would reveal any warming/cooling trends. Compared to most liberal projects, it wouldn't even be particularly expensive.
Yet, none of the libs propose such a project. It's almost like they don't want to know. Half-baked, feel-good science is a religion to them, and many seem to be so gullible and simple-minded, they need to "believe" much more than the need to know the truth.