Really like the diagram[1] (which I found the source in [2]. Another one on Wikipedia[3]. What's not clear is how is this changing over time? Given the greenhouse gas narrative (which I accept), how has the "back radiation" changed over time? Over the last century is it +0.1%, +1%?

1: https://camo.githubusercontent.com/55b611b5709a0e90b7e9ee319...

2: http://www.cgd.ucar.edu/staff/trenbert/trenberth.papers/BAMS...

3: https://en.wikipedia.org/wiki/Earth%27s_energy_budget#/media...