The final version of "Target Atmospheric CO2: Where Should Humanity Aim?" in The Open Atmospheric Science Journal is available at 
http://dx.doi.org/10.2174/1874282300802010217
http://dx.doi.org/10.2174/1874282300802010217
You can click on the main paper and supporting material individually. The two are combined in one pdf on the GISS web site at
http://pubs.giss.nasa.gov/abstracts/2008/Hansen_etal.html BTW, I think that the Supporting Material contains some interesting stuff.
NASA decided not to make a press release for the paper, but Yale did one
http://www.eurekalert.org/pub_releases/2008-11/yu-rts110708.php The draft press release that I wrote and "Q&A" about the paper are at http://www.columbia.edu/~jeh1/mailings/20081030_Target.pdf It is difficult to generate the attention that the topic deserves because the basic conclusions were already presented in my talk at the December 2007 AGU meeting. Also the first draft of the paper (available in arXiv, as is the final version) appeared on several blogs and was discussed in several newspapers, which discourages media attention to the final improved version.
The long delay between first draft and final paper was my fault. The principal demand of the journal referees, addition of a "caveats and uncertainties" section (section 4.5 in the main paper and section 18 in the Supplementary Material), could have been completed in a week or two, but it took me ~two months because of other obligations. I caused another delay by not checking typesetting in the proofs carefully enough, requiring an extra iteration of proofs. Bottom line: I think that the "Open" publication method, which includes full peer review but results in a paper freely available throughout the world, is promising and I intend to pursue it further.
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