That pesky Antarctic

A careful new reconstruction of the Antarctic climate record confirms much of what skeptics have been saying. They found evidence of a medieval warm period ("between 300 and 1000 CE") and the Little Ice Age ("1200 to 1900 CE") and show some recent warming as a rebound off the LIA.  They also show that the Antarctic peninsula -- the Warmist's favorite bit of Antarctica  -- is anomalous. I have often pointed to subsurface vulcanism as an influence on peninsula temperatures.  I have truncated the Abstract below at the point where they leave the facts and drift into speculation

Antarctic climate variability on regional and continental scales over the last 2000 years

Barbara Stenni plus Uncle Tom Cobleigh and all


Climate trends in the Antarctic region remain poorly characterized, owing to the brevity and scarcity of direct climate observations and the large magnitude of interannual to decadal-scale climate variability. Here, within the framework of the PAGES Antarctica2k working group, we build an enlarged database of ice core water stable isotope records from Antarctica, consisting of 112 records. We produce both unweighted and weighted isotopic (? 18O) composites and temperature reconstructions since 0 CE, binned at 5- and 10-year resolution, for seven climatically distinct regions covering the Antarctic continent. Following earlier work of the Antarctica2k working group, we also produce composites and reconstructions for the broader regions of East Antarctica, West Antarctica and the whole continent. We use three methods for our temperature reconstructions: (i) a temperature scaling based on the ? 18O–temperature relationship output from an ECHAM5-wiso model simulation nudged to ERA-Interim atmospheric reanalyses from 1979 to 2013, and adjusted for the West Antarctic Ice Sheet region to borehole temperature data, (ii) a temperature scaling of the isotopic normalized anomalies to the variance of the regional reanalysis temperature and (iii) a composite-plus scaling approach used in a previous continent-scale reconstruction of Antarctic temperature since 1 CE but applied to the new Antarctic ice core database.

Our new reconstructions confirm a significant cooling trend from 0 to 1900 CE across all Antarctic regions where records extend back into the 1st millennium, with the exception of the Wilkes Land coast and Weddell Sea coast regions.

Within this long-term cooling trend from 0 to 1900 CE, we find that the warmest period occurs between 300 and 1000 CE, and the coldest interval occurs from 1200 to 1900 CE.

Since 1900 CE, significant warming trends are identified for the West Antarctic Ice Sheet, the Dronning Maud Land coast and the Antarctic Peninsula regions, and these trends are robust across the distribution of records that contribute to the unweighted isotopic composites and also significant in the weighted temperature reconstructions.

Only for the Antarctic Peninsula is this most recent century-scale trend unusual in the context of natural variability over the last 2000 years.


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