The fact is, there has been global warming, in which CO2 has played a modest but significant role. However, the contribution of human-generated carbon dioxide (CO2), or carbon dioxide of any kind, to further warming is diminishing with increasing rapidity and must eventually cease.

Global warming, technically Radiative Forcing (RF), occurs when greenhouse gases like CO2 absorb the earth’s infrared radiation and convert it to heat before it can escape into outer space. CO2 only absorbs infrared in two narrow frequency ranges, and there is only so much earthly radiation in those ranges. As CO2 increases in the atmosphere, it absorbs ever greater percentages of that radiation. When it is used up (reaches “saturation”), RF from CO2 must necessarily cease. CO2 has already fully absorbed the most easily absorbed frequencies and as it uses up the rest further heating from it becomes increasingly difficult, the additions to RF therefore slow, and full  saturation draws ever closer. So, there is a natural limit to how much CO2 can contribute to temperature, and to how quickly.

The charts below will be useful references for the reader.