To be frank, I think these emails to be incredibly damaging to global warming, and to science in general. I haven't heard about any tampered data, or falsified results, but it's looking like there was squashing of dissenting view-points through the peer-review process. You tamper with peer-review and you screw up science's check and balance. Even if the emails turn out only to be about personal animosity, rather than a professional blocking, what the general public will remember is "Global warming is a hoax and you can't trust science."
I will be interested in finding out exactly what the emails say, and what research, if any, is made void. Afterall, if all they were doing was blocking certain research from being published, then publishing that research should right the wrong. There is still a large volume of research supporting human-aided global warming, and it is only nullified if the results were skewed.