text: Q: Dr. S. Fred Singer: Perhaps to clarify the discussion. We need to separate these results of model experiments - of course that's all they are are experiments with models, from scenarios of how CO2 will increase. These are two separate issues. As far as I can tell from the IPCC report, their estimate or their numbers for the what is call the "climate sensitivity" that is, how much temperature rise will be produced by doubling of CO2 alone, all other things being equal, has not changed since 1990. It is still estimated to be between 1.5 and 4.5 C for a doubling of CO2. And what Roy has addressed here is the fact that this is probably a faulty estimate because they have not taken into account the reduced feedback, perhaps even negative feedback, of water vapor and reduced, perhaps even negative feedback of clouds. So the climate sensitivity is the one we are interested in. I think many of us believe that these numbers, that the IPCC has given, are just plain wrong.