Email 3461, May 2001, Ed Cook: "I do think that there still exists a signficant uncertainty as to the relative contributions of natural and greenhouse forcing to warming during the past 20-30 years at least."

Email 3461

I think that most researchers in global change research would agree that the emergence of a clear greenhouse forcing signal has really only occurred since after 1970. I am not debating this point, although I do think that there still exists a signficant uncertainty as to the relative contributions of natural and greenhouse forcing to warming during the past 20-30 years at least.