T represents the amount of energy available from all sources to maintain the constant flow that keeps the atmosphere off the surface AND achieves radiative balance at the top of the atmosphere. (newclimatemodel.com)
And for temperature to rise at the surface there has to be an increase in energy available at the surface and that demands that some of the clouds disappear. (judithcurry.com)
We use them to represent the amount of energy available in food and beverages. (verywellfit.com)