An ageing gent says he does not accept this statement:

```
It's a fact that greenhouse gases, predominantly water vapour, keep the Earth 
from being hostile and cold; that CO2 albeit in trace quantities is also a 
greenhouse gas and therefore helps keep the planet warm...

```

I know no more about why he rejects this statement - maybe it is that water vapour alone would do the job. The gent in question has a first class degree and a doctorate in physics. 

Is there a debate within the physics community over this or am I misunderstanding?