The key is to include "life cycle analysis" into the search string. Google Scholar gives quite a number of references: http://scholar.google.com/scholar?hl=en&q=life+cycle+GHG+analysis+wind+turbines&btnG=Search&as_sdt=80000000000&as_ylo=&as_vis=0. Do you have access to top publications? If not, I could upload those for you.