*Everyone in the room agrees that CO2 does absorb infrared radiation, as observed in the lab

*I think everyone in the room agrees that the greenhouse effect (however badly named) does occur in practice: our planet and the others with an atmosphere are warmer than they would be because of the presence of water vapour and CO2

*I'm not sure if everyone agrees that the effect does not saturate with increasing CO2, but we heard a very clear presentation about that from Francis Farley

Professor Farley's explanation was to imagine CO2 as being like ink poured into water. You can add more and more ink and so there is no end to the extra absorbtion you can get. Saturated absorbtion bands are a red herring. This assessment made sense to me.

I've set up a separate thread because I imagine some people will want to discuss this.

*It seemed that everyone in the room agreed that the CO2 concentration in the atmosphere has risen significantly over the last 200 years

*Almost everyone in the room agrees that this is because of anthropogenic emissions (fossil fuels, cement production, forest clearance).  We did hear Ian Plimer arguing that volcanic emissions of CO2 are more important than most scientists claim, but he did not explain why they would have changed in a step-like fashion in 1800, after tens of thousands of years with no such changes; and even he agreed that some of the increase in CO2 is anthropogenic.

This is not an area I've ever questioned, but I'm looking forward to finding out more from Ian Plimer about his ideas. I'm not sure I understand Dr Wolff's reference to 1800 either.

***I then suggested that if we agree all these statements above, we must expect at least some warming.  

Then moving to whether we already see effects:

*I think everyone in the room agrees that the climate has warmed over the last 50 years, for whatever reason: we saw plots of land atmospheric temperature, marine atmospheric temperature, sea surface temperature, and (from Prof Svensmark) ocean heat content, all with a rising trend.
(I briefly touched on the idea, mentioned only by Dr Howard in his introduction, that warming has stopped since 1998.  I used the analogy that it was very warm over Easter, but then cool enough that I had to scrape my car the following week.  But we did not take this as evidence against the idea that we are on a warming trend into summer, in which we know that July will be warmer than June than May than April, etc.).

Yes, but I would like to get some idea of whether the warming we have seen is statistically significant. i.e. a response to Doug Keenan's article in the WSJ. 

I think Lucia's work has shown fairly clearly that the trend since the start of the century is very unlikely under 2deg/century, so the analogy is not a good one.

*We probably don't agree on what has caused the warming up to now, but it seemed that Prof Lockwood and Svensmark actually agreed it was not due to solar changes, because although they disagreed on how much of the variability in the climate records is solar, they both showed solar records without a rising trend in the late 20th century.

 I didn't take this on board at the time. It would be interesting to see Svensmark's opinion. If the warming really cannot be shown to be statistically significant, how important is this kind of attribution?

*On sea level, I said that I had a problem in the context of the day, because this was the first time I had ever been in a room where someone had claimed (as Prof Morner did) that sea level has not been rising in recent decades at all.  I therefore can't claim we agreed, only that this was a very unusual room.

 Not something I know much about, but Morner's concerns seem important. I find the idea that we can't see the adjustments to the data disturbing.

*However, I suggested that we can agree that, IF it warms, sea level will rise, since ice definitely melts on warming, and the density of seawater definitely drops as you warm it.

*Finally we come to where the real uncertainties between scientists lie, about the strength of the feedbacks on warming induced by CO2, with clouds a particularly prominent issue because they have competing effects that are hard to quantify.  I suggested to the audience that we could probably agree that the likely range of warming from a doubling of CO2 was 2-4.5 degrees C (which is actually the IPCC range).  This was the first time I really got any dissent, so I then asked whether we could all agree on at least 1 degree (implying no positive feedbacks at all, even from increased water vapour and sea ice loss).  I got one dissenting voice for that, but there wasn't a chance to find which of the preceding statements he had disagreed with (it would be necessary to disagree somewhere up the line to be consistent with dissenting on this one).

I'm very uncomfortable about the idea of making a prediction about temperature when it is so likely that there is something missing from the models - this seems the most plausible explanation for the temperature trend since 2000/1.

Under the scientific method, shouldn't we find out what this is before we start testing again?

We may be able to agree that the no-feedback warming is 1 degree C, but there is a great big unknown in the shape of the feedbacks. The idea of overall positive feedbacks seems unlikely to me, given that the Earth's temperature doesn't seem to have got out of control in the past.