It is doubtful that any method of global infilling of temperatures based on the limited observational coverage available in the second half of the 19th century or (to a decreasing extent) during the first half of the 20th century is very reliable. (climateaudit.org)
While the question of infilling data in this way is fraught with difficulty at the best of times, the effect in the case of Briffa series was remarkable. (wattsupwiththat.com)
[5] Tapio Schneider developed RegEM, an impressive ridge - regression based algorithm for infilling missing data. (judithcurry.com)