I was pleased by your inclusion of the following comment:

“Conclusion

1) The IPCC claims that most of the warming, not all of it, is attributable to human activities. It doesn’t say that all of the warming is because of rising CO2. Yet the IPCC model average “quietly assumes” that all of the past warming was because of rising CO2 equivalents.”

My comment:
There are probably many well-informed scientists (I am one) who (a) have no objection to the postulate that regional and possibly global mean surface temperatures have been increased during the second half of the 20th century as a result of human activities, but who (b) see little or no grounds in the published literature, including the IPCC Working Group 1 reports, to attribute a more than a small amount of such recent warming to increases on the carbon dioxide (CO2) content of the earth’s atmosphere.
The IPCC has, as in the passage you quote, for some reason tended (or even tried?) to blur the distinction between anthropogenic CO2 emissions and other anthropogenic climate forcings such as land use changes. Why is IPCC doing this? Is it just sloppy editing or is it a conscious decision to muddy the waters?
By failing to refer to the abundant corpus of detailed, authoritative, peer-reviewed and published work on land use change as a climate forcing such as that of Roger Pielke Sr and his co-workers, the IPCC is failing in its appointed – and seemingly well-funded – task and leaves itself open to charges of trying to advance a particular agenda by stealth.
I’m not a climatologist, but if I was I’d be wary of too close an association with this quasi-political organisation, even if that meant missing an opportunity for career advancement. I’d prefer to keep my distance from IPCC – and retain my scientific independence. I take my science too seriously to do otherwise.