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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.
Abstract: Solar variability is controlled by the internal dynamo which is a nonlinear system. We develop a physical-statistical method for forecasting solar activity that takes into account the non-linear character of the solar dynamo. The method is based on the generally accepted mechanisms of the dynamo and on recently found systematic properties of the long-term solar variability. The amplitude modulation of the Schwabe cycle in the dynamo's magnetic field components can be decomposed in an invariant transition level and three types of oscillations around it. The regularities that we observe in the behaviour of these oscillations during the last millennium enable us to forecast solar activity. We find that the system is presently undergoing a transition from the recent Grand Maximum to another regime.
This transition started in 2000 and it is expected to end around the maximum of cycle 24, foreseen for 2014, with a maximum sunspot number Rmax = 68 plus/minus 17. At that time a period of lower solar activity will start. That period will be one of regular oscillations, as occurred between 1730 and 1923. The first of these oscillations may even turn out to be as strongly negative as around 1810, in which case a short Grand Minimum similar to the Dalton one might develop. This moderate to low-activity episode is expected to last for at least one Gleissberg cycle (60 - 100 years). See full paper PDF here.