Back in early November, I noted information suggesting hydropower may not be as carbon neutral as we thought. The word "may" was deliberately chosen.
At the time, I received an angry email from a leading hydropower supporter, which included links to some studies suggesting the data for high emissions was cherry-picked, or didn't take net emissions into account adequately.
I soon found other studies dealing with these objections and suggesting significant net emissions from hydropower. At this point, I was reminded of the debate between warming deniers and climate scientists, except I was not sure which side was which.
The December 2006 issue of Nature contains a fascinating article on the subject: "The green image of hydropower may have been seriously overstated, warn Scientists." The key paragraphs: