I don't know why these scientists feel they have to do this. I can't see how it benefits them. If their conclusions are correct and accurate you shouldn't have to do any political posturing, and the data should really speak for itself. When you get into this, it seems like the risks of getting caught far outweigh the benefits of exaggeration.
However, I do know the Himalayan Glacier report was specifically used to gain EU research funds, so it could have been a business decision. But that's a whole other issue.