I got pointed to the following   lecture by Professor Tennyson  as Univeristy College London

http://www.ucl.ac.uk/lhl/lhlpub_spring09/09_240209

I came to the conclusion that  water vapour is  a stronger green house gas than previously believed ?

 Is this a correct interpretation  - if so  would it be fair to say that  CO2 warming may  cause some extra problems as water vapour levels increase ?

PeteM,

Haven't taken the time to view the talk; but you questions puzzle me.

Water vapor has always been regarded as the major greenhouse gas; but its impact is not increasing much, because its concentration is linked to average temperature.

As global temperatures rise, the water vapor concentration and impact will also increase. So there is a well-known enhancement of the direct CO2 impact.

Thanks -  that's my understanding  .

The interesting thing in the talk is that   Prof Tennyson's  research  ( from a few years ago)  has  found that water vapour is a slightly stronger absorber of IR radiation than  the  data previously logged in the HITRAN database indicated.

This was a combination of  not enough details in the known bands and  understimates of  some of the absoption properties.

So my  musing  (and I'm an amateur here)  was that a bit more water vapour in the air ( due to CO2 warming etc )  will have a slightly stronger   water vapour warming  which  implies some ( small)  extra greenhouse warming ...

Interesting lecture.

It does seem like they are inferring water vapour is a bit more potent.

About 11 W/m² for the missing spectra?

He was also saying that other groups are gradually increasing their figures towards Prof Tennysoons numbers.

It is interesting that water has the capacity to exist in extreme temperature environments.
Maybe there is still some small amounts on Venus?