Despite most of my fellow scientists thinking I've been involved in the IPCC process before, this time for AR4 is my first. The main benefit is that the science produces an assessment (and associated summaries) for the govts and policy types....As Kevin may have said to you, we have a very mixed bag of LAs in our chapter. Being the basic atmos obs. one, we've picked up a number of people from developing countries so IPCC can claim good geographic representation. This has made our task harder as CLAs as we are working with about 50% good people who can write reasonable assessments and 50% who probably can't. Getting them all involved has been a challenge, and we've not really succeeded. Our LAs are unlikely to cause us much of a problem. Problems will start when the first order draft (after our next meeting in May) goes our for review by all and sundry (any scientists anywhere) - sometime in the late summer. This is when the skeptics and scientists who'll think we've misrepresented or ignored their views get a chance to tell us. We have to respond to all. We have an excellent group of Review Editors to help us here - when we meet in NZ in Dec 05. I expect that will be an interesting meeting. Getting our less good LAs involved will be an issue. Susan Solomon is keen for them to be involved, but many lack global perspectives and a sense of what the big issues are.
Issues are (and could have been predicted before we started) : 1. How much has the world warmed? Errors attached to all observations. Issues of representativeness - why urbanizaton and land-use changes are not that important. A small group of skeptics will likely have a go at us on this. I hope we have all our bases covered. 2. Surface warming yet lower troposphere not warming as much. A US report (CCSP) Kevin can tell about will help here, but our likely conclusion that this issue is resolved will likely come in for lots of flak. Explaining why we think we're right will be the biggest issue - making sense of diverse datasets and saying why we think some are right and some have problems. 3. Extremes. There is a lot more information out there this time from initiatives made by earlier assessments. Bringing all this together is the challenge here, and saying defensible statements. 4. We have a chance this time to go into a lot more detail about indices (ENSO,NAO etc) and their roles. We will be endorsing GCOS initiatives to improve the network and saying that reanalyses in the future have to really consider issues of changing data inputs. They can do this by running periods with/without specific datasets to see effects. Getting people to think this way is coming, but resources are an issue. Computers getting faster,but we must use this to address the above issues,rather than using the additional speed to improve resolution. We can do both but we need good planning and it will all take time. If you want to clarify anything then email me again. We are 7 hours ahead and I tend to work 8 till 4.30 which makes catching me difficult.