Jean-Pascal van Ypersele, the deputy leader of the Intergovernmental Panel on Climate Change (IPCC).
van Ypeersele also apparently saw nothing wrong over Pachauri using the word "voodoo science" to slam India's Environment ministry which contested the UN body's claim.
The UN's climate science body is under attack after being forced to retract claims that the Himalayan Glaciers would melt by 2035. The 2007 report, that included the Himalayan claim, is the basis for the current international debate on climate change.
However, van Ypersele told the BBC it was simply a "human mistake", the Daily Telegraph reported.
"Aren't mistakes human? Even the IPCC is a human institution and I do not know of any human institution that does not make mistakes, so of course it is a regrettable incident that we published that wrong description of the Himalayan glacier," he said.
The scandal has led to calls for Pachauri to resign after he described those who criticised the claim as using "voodoo science". India's Environment ministry had contested the IPCC's projection of Himalayan glaciers melting by 2035.
Again, van Ypersele, professor of climatology and environmental sciences at the Catholic University of Louvain, said it was "only human" to use such language.
"I would personally not have used the voodoo science wording," van Ypersele said. "I think humans can sometimes use words that are a bit too strong but it is certainly not a reason to ask for the resignation of a chairman who has done an excellent job.
We are trying to do our best, we are going to reinforce the review procedures so the probability in the next report of such incidents happening is even lower. But to guarantee a zero fault product is probably not possible for any human enterprise."
van Ypersele said the panel made up of more than 2,000 scientists will do everything it can to ensure there are not mistakes in the new report, although he emphasised that no scientist can promise a perfect document.
"We are trying to do the best job we can in assessing the quality information about climate change issues in all its dimensions and some do not like the conclusions of our work. Now it is true we made a mistake around the glacier issue, it is one mistake on one issue in a 3,000 page report. We are going to reinforce the procedures to try this does not happen again."
There are fears that the scandal has damaged confidence in the IPCC and ultimately in the science of global warming but van Ypersele claimed it had in fact strengthened the case for tackling climate change.
"I would like to submit that this could increase the credibility of the IPCC not decrease it. Why is that? Would you trust someone who has admitted an error and is ready to learn from his or her mistake or someone who claims to be unassailable? The IPCC does not claim to be unassailable, when there is a good reason to admit a mistake we do it, but for the rest of IPCC conclusions we stand by it very strongly," he said.