Gill is located on the Ross Ice Shelf at 79.92S 178.59W 25M and is completely unrelated to Harry. The 2005 inspection report observes:So not only is there a splice error, but the data itself may have been biased by snow burial.2 February 2005 - Site visited. Site was difficult to locate by air; was finally found by scanning the horizon with binoculars. Station moved 3.8 nautical miles from the previous GPS position. The lower delta temperature sensor was buried .63 meters in the snow. The boom sensor was raised to 3.84 m above the surface from 1.57 m above the surface. Station was found in good working condition.I didn't see any discussion in Steig et al on allowing for the effect of burying sensors in the snow on data homogeneity.
The difference between "old" Harry and "new" Harry can now be explained. "Old" Harry was actually "Gill", but, at least, even if mis-identified, it was only one series. "New" Harry is a splice of Harry into Gill - when Harry met Gill, the two became one, as it were.
Considered by itself, Gill has a slightly negative trend from 1987 to 2002. The big trend in "New Harry" arises entirely from the impact of splicing the two data sets together. It's a mess.