Over at the matchless blog Wattsupwiththat:
Look for two comments by Mohib (21:33:01) on 1st Feb – I thought Mohib’s questions were important enough to try and explain the history .
Jones et al 1986 did indeed reject 38 stations from their Northern Hemisphere study. Note UHI not actually mentioned in the 1986 Table 1 – but no doubt covered under “non-climatic warming trends” – so a nuance there compounded by PDJ ref to “affected by urbanization” in the ClimateGate mails 1184779319.txt link at Watts.
Nth Hem Journal paper pdf downloadable here
TR022 Nth Hem documentation book partly online with 2 tables showing the breakdowns of their station numbers in each homogenization category.
38 stations UHI affected out of the thousands of NH cities is somewhat laughable and the paper should have been sent back by the editor or reviewers. But Jones could say that other UHI affected data were caught up in other checks of his and rejected for other reasons, eg. Category D maybe.
BTW Geoff Jenkins was one of the original 1990 IPCC authors and you might expect would know these things.
In the case of the Jones et al 1986 Southern Hemisphere Journal paper downloadable and TR027 book fully online.
Jones et al found only 3 (yes three) UHI affected stations to reject. Even more surreal than 38 – 3 out of what, 120 plus major cities in the Sth Hem.
So there are a few “nuances” to comprehend in the statements such as “On the one hand in 1986 he knows UHI affects the temperature..”.
IMHO Jones et al 1986 spoke and did less than the bare minimum required to be able to claim that they had adequately dealt with the UHI in global T data.
There was presumably some disquiet remaining in climate circles after the 1988 publication of Wood’s critique of Jones et al 1986. Otherwise, how do you explain the need for the Jones et al 1990 Letter to Nature at al ?
In the 1990 Letter to Nature they compared purportedly rural series from 3 regions, Western USSR, Eastern China, Eastern Australia – with their grid point trends from those same regions and claimed to prove that negligible UHI effect remained in their grid point trends – a conclusion the IPCC and UKMO has quoted ever since.
In fact what happened IMHO (and I did share in a work checking what they did in Eastern Australia) – was that their Rural series contained significant UHI amplification in the trend – hence they were able to demonstrate tolerable agreement with their grid points trends which also carry UHI contamination.
So Mohib, when you say above; “But then in his 1990 paper he takes the position with Wang that UHI is not a factor in temperatures.” Can you see now that is not a fair summing up of the situation.
In fact Jones et al 1990 was purporting to demonstrate that Rural series had similar trends to his grid point series – ergo by their reasoning there can not be significant UHI effect in either. I hope that that explain it clearer.
Jones et al 1990 is now further unraveling helped along by Doug Keenans persistence and events revealed in Climategate emails. That all these prominent co-authors lent their names to the shoddy 1990 Letter to Nature is a classic case of IPCC science at work.