However, I can safely announce the existence of the paper, since Dr. Mann has already effectively broken the embargo by advertising the existence of the paper on his own website in his curriculum vitae (CV).
You can read his CV here: http://www.meteo.psu.edu/~mann/Mann/cv/cv.html
The paper is:
Kemp, A.C., Horton, B.P., Donnelly, J.P., Mann, M.E., Vermeer, M., Rahmstorf, S., Climate related sea-level variations over the past two millennia, Proc. Nat. Acad. Sci. (in press)
By placing this on his website, Dr. Mann appears to have jumped the starting gun a bit, since I can not find any existence of the paper in any of his co-author websites or anywhere else on the web for that matter:
While I can’t say anything about the contents of the paper or the press release, I can tell you that very little has changed in the pursuit of the hockey stick.
I’ll have the full report tomorrow when the PNAS embargo is lifted at 1500EST.