Marcott, Shakun, Clark and Mix did not use the published dates for ocean cores, instead substituting their own dates. The validity of Marcott-Shakun re-dating will be discussed below, but first, to show that the re-dating “matters” (TM-climate science), here is a graph showing reconstructions using alkenones (31 of 73 proxies) in Marcott style, comparing the results with published dates (red) to results with Marcott-Shakun dates (black). As you see, there is a persistent decline in the alkenone reconstruction in the 20th century using published dates, but a 20th century increase using Marcott-Shakun dates. (It is taking all my will power not to make an obvious comment at this point.)
Marcott et al archived an alkenone reconstruction. There are discrepancies between the above emulation and the archived reconstruction, a topic that I’ll return to on another occasion. (I’ve tried diligently to reconcile, but am thus far unable. Perhaps due to some misunderstanding on my part of Marcott methodology, some inconsistency between data as used and data as archived or something else.) However, I do not believe that this matters for the purposes of using my emulation methodology to illustrate the effect of Marcott-Shakun re-dating.