It's gotten brighter over even just the last 20 million years. The ice caps helped reflect nearly .39 of it, but soot and melting are lowering that. It's called

It's gotten brighter over even just the last 20 million years. The ice caps helped reflect nearly .39 of it, but soot and melting are lowering that. It's called albedo and that loss will dwarf the CO2 Heat trapping.