Richard Muller sent me the BEST list of “very rural” sites – see http://www.climateaudit.info/data/station/berkeley.
I took a quick look at the “very rural” stations in two tropical countries – Peru and Thailand – in order to groundtruth their classification methodology. These two examples were chosen because several years ago, I looked at Hansen’s “rural” Peru stations, most of which were actually urban; and because one of my sons is in Thailand.
Berkeley classified only two stations in Peru as “very rural” – Huanuco and Quince Mil. However, the population of Huanuco, according to GeoNames, is 147959; it was classified by Hansen as urban. Why the Berkeley algorithm classed it as “very rural” is unclear. Quince Mil is a small town recently featured in Time magazine here. The Berkeley record only has a few sporadic values after the mid-1980s. The BEST urban-rural comparison in Peru looks to me like it has no meaning.
The Berkeley classification in Thailand also looks very suspect. As in Peru, many of the “very rural” sites are small cities. Some locations look suspicious. “Bangkok Pilot” is shown as “very rural”, but when googled is associated with Suvarnabhumi, the name of the very urban Bangkok airport (data is sparse, so it may be something else, but anything associated in any way with Bangkok can hardly be “very rural”)
There are five “very rural” Thailand sites with a minimum of 120 values: PHETCHABURI (population 46,501), KO LANTA (population 20,000), TAKUA PA (population 35,337), KO SAMUI (population 50,000) and MAE HONG SON, a relatively long record in the northwest hill country near the Myanmar border. (We visited Pai which is near there a couple of years ago.) A picture Mae Hong Son airport is shown below:
The CRU stations in the CRU gridcell are all highly urban: BANGKOK METROPOLIS (!), ARANYAPRATHET (population 73813), CHANTHABURI (population 488397), SIEMREAP (population 85,000), KAMPOT (poluation 39186), PHNOM-PENH (!). Although we keep hearing of the unimportance of UHI, Bangkok has increased 0.24 deg C/decade relative to Mae Hong Son.