When scientists first disputed that part of the report in 2007, he dismissed their statements as "voodoo science". A few months later it was revealed to be the exact opposite; instead, that part of the 2007 IPCC report was voodoo, simply being a statement made to a journalist.
"I had absolutely no idea what was coming. It just sort of escalated," Pachauri told Suzanne Goldberg of the Guardian. "In retrospect we should have had a much better capacity at the IPCC to deal with this kind of thing," he said more recently.
Here's an idea, and it was reaffirmed by the committee the UN asked to evaluate the IPCC (see InterAcademy Council Report Urges 'Fundamental Reform' Of IPCC) - you won't have to deal with this kind of thing if you don't allow Working Groups to cite 'gray literature' from unpublished or non-peer-reviewed sources as fact. And don't let them assign high confidence to statements for which there is little evidence.
Has he learned anything? It seems not, he remains firm in his belief that "existing IPCC procedures were already stringent enough to catch future mistakes" even though they had not in the past.
Like Nancy Pelosi in the United States for her political party, Pachauri is a lightning rod for criticism the IPCC does not need as it salvages its reputation in the eyes of a segment of the population who will be much harder to convince in the future (though some of them were never going to be convinced anyway) but he emerged from the last meeting still in charge because the IPCC believes they have to gloss over and rationalize every mistake and deception or "deniers win" - that's a bad recipe for getting the correct science policies implemented.