I have just noticed an article by Jeff Id at “WattsUpWithThat” that says the BEST project analysing global temperature records – does this – “They detect steps in the data, chop the series at the steps and reassemble them.”
Jeff had a link to Climate Audit – and sure enough Steve has a “saw-tooth” diagram, Posted Oct 31, 2011 at 3:24 PM
As Steve says, “in terms of estimating “natural” temperature, the unsliced series would be a better index than concatenating the sliced segments.” Dead right.
As far as I can tell, this diagram expresses exactly what the two GISS diagrams did in 2001 – see from Hansen, J.E., R. Ruedy, Mki. Sato, M. Imhoff, W. Lawrence, D. Easterling, T. Peterson, and T. Karl 2001. A closer look at United States and global surface temperature change. J. Geophys. Res. 106, 23947-23963, doi:10.1029/2001JD000354. and a pdf can be downloaded.
I have a page here explaining the thing –
Also a blog post.
I thought I read where BEST does NOT reassemble the pieces after they are cut so some of what you discuss is not an issue with them. Of course, we are left with the full UHI effect with BEST methodology and a slight warming due to the method, which may be why they are showing more warming than the other ground records.
climateaudit.org/2011/10/31/best-menne-slices/
You should also read my critique of BEST and other datasets that us minimum and maximum temperatures.
www.bishop-hill.net/blog/2011/11/4/australian-temperatures.html
This little 9 page PDF paper How to interpret Temperature trends – kindly sent in by Sandy McClintock.
There is also an Urban Irrigation Effect in some locations.
You can see it clearly in the Perth temperature record.
From 1967 to 1994 the official Perth weather station was on Wellington Street, across the road from a large urban park that was irrigated several nights a week in summer.
Minimum temperatures were about 2C higher during this period and immediately fell when the station was moved to an unirrigated location at Mt Lawley.
www.waclimate.net/perth-temperature-history.html