Scientists who are nominated but not selected as authors are invited to register as expert reviewers for the report. (ipcc.ch)
Instead, the authors are at perfect liberty to ignore comments submitted in good faith by expert reviewers — to decide that the source they've cited is probably right. (nofrakkingconsensus.com)
There are three stages of review involving more than 2,500 expert reviewers who collectively submitted 90,000 review comments on the drafts. (realclimate.org)