Yes, but that's the same thing, they're doing double counting.

Another failed debunking-the-debunkers attempt by Skeptical Science:
----------------------
Myth: Each unit of CO2 you put into the atmosphere has less and less of a warming impact. Once the atmosphere reaches a saturation point, additional input of CO2 will not really have any major impact.

It's like putting insulation in your attic. They give a recommended amount and after that you can stack the insulation up to the roof and it's going to have no impact." (Marc Morano, as quoted by Steve Eliot)
----------------------
The mistaken idea that the Greenhouse Effect is 'saturated', that adding more CO2 will have virtually noeffect, is based on a simple misunderstanding of how the Greenhouse Effect works.

The myth goes something like this:
* CO2 absorbs nearly all the Infrared (heat) radiation leaving the Earth's surface that it can absorb. True!
* Therefore adding more CO2 won't absorb much more IR radiation at the surface. True!
* Therefore adding more CO2 can't cause more warming. FALSE!!!

Here's why; it ignores the very simplest arithmetic...

The air doesn't just absorb heat, it also loses it as well! The atmosphere isn't just absorbing IR Radiation (heat) from the surface.

It is also radiating IR Radiation (heat) to Space. If these two heat flows are in balance, the atmosphere doesn't warm or cool - it stays the same.

Similarly we can change how much heat there is in the atmosphere by restricting how much heat leaves the atmosphere rather than by increasing how much is being absorbed by the atmosphere.

That's the same thing! If more warmth is absorbed then, by definition, less is radiated. You can't add the two together. It's like saying "I earn £2,000 a month and spend £2,000 a month, so each month I earn £4,000."