New Computer Fund

Friday, June 3, 2016

Marcott v Rosenthal

"To the extent that our reconstruction reflects high-latitude climate conditions in both hemispheres,
it differs considerably from the recent surface compilations, which suggest ~2°C MWP to LIA cooling in the 30°N to 90°N zone, whereas the 30°S to 90°S zone warmed by ~0.6°C during
the same interval (24). In contrast, our composite IWT records of water masses linked to NH and
SH water masses imply similar patterns of MWP to LIA cooling at the source regions The inferred
similarity in temperature anomalies at both hemispheres is consistent with recent evidence from
Antarctica (30), thereby supporting the idea that the HTM, MWP, and LIA were global events."

Rosenthal et al. 2015

Fig. 2. Comparison between Holocene reconstructions of surface and intermediate-water temperatures.
(A) Global (red) and 30°N to 90°N (green) surface temperatures anomalies, (B) 30°S to
90°S surface temperature anomalies (24), (C) changes in IWT at 500 m, and (D) changes in IWT at
600 to 900 m. All anomalies are calculated relative to the temperature at 1850 to 1880 CE. Shaded
bands represent +/- 1 SD. Note the different temperature scales.

Panels A and B are from the Marcott et al 2013 paper and include the spurious uptick caused by lack of data and their method.  btw, that +/- 1 SD should not be confused with actual uncertainty because there are huge unknowns, but this is about as good as it gets for now.

A denizen posted the Marcott cartoon as a sort of gotcha then asked what I thought was a better reconstruction.  I offered Rosenthal et al. 2015 even though it has issues because there isn't a paleo reconstruction that doesn't have issues.  The Rosenthal, Oppo and Lindsey crew just happened to take a polite counter opinion of Marcott et al which carries a bit more weight than any of my ramblings.  Kind of entertaining that the denizen liked the Rosenthal paper because he thought the Marcott et al. reconstructions matched Marcott et al. reconstructions :)  Hopefully that denizen will get around to reading the text.

Fig. 3. Temperature anomaly reconstructions for the Common era relative to the modern data (note
that the age scale is in Common era years with the present on the right). (A) Change in SST from the
Makassar Straits [orange, based on (26) compared with NH temperature anomalies (27, 28)]. (B) Compiled IWT anomalies based on Indonesian records spanning the ~500- to 900-m water depth (for individual records,  see fig. S7). The shaded band represents +/- 1 SD.

They also include a comparison of Oppo et al. 2009 with Mann and Moberg similar to comparisons I have made but with a less dramatic scale, in the left hand figure.

Depending on which product you prefer and the current state of adjustment, the IPWP correlates well with global SST which is 70% of the GMST product.  Since HADSSTi uses less creative interpolation it is a better match for the reconstruction in the region of the reconstruction 3S-6S and 107E to 110E.

Since there are tons of issues in paleo to deal with, every reconstruction will need some time to resolve them, but Rosethal and crew appear to be ahead of the learning curve.

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