The transition from primarily bucket measurement in 1970 to primarily engine inlet in 2000 was supported by the following graphic in Kent et al 2007 discussed in last year's posts e.g. here: (climateaudit.org)
Meanwhile, the paint bucket measurement of the commodity remained at N800 as at last week. (ghanapoliticsonline.com)
These effects have been quantified; for example engine room intake (ERI) temperatures have been compared to bucket measurements by a number of studies. (skepticalscience.com)