Re: Was the ClimateGate Hacker Justified? Join the Debate!

[Wes Deviers <wdevie () hrcsb org>]

On Thursday 03 December 2009 10:08:03 am Valdis.Kletnieks () vt edu wrote: 
> > 4) Do you know that most of temperature measurement is done in urban 
> > areas, biasing the measurement?
>
> I'm pretty sure everybody is pretty aware it's warmer in the cities, that
> effect has been understood for centuries. Heck, my local TV weatherman
> will say stuff like "It's going to be about 90F here in Roanoke, and a
> little cooler out in the countryside" or even "Driving conditions here
> in the city should be OK, but the roads in outlying areas will be freezing
> up".
>
> So you're saying that a TV weatherman at a small station knows more
> about weather prediction than the guys at IPCC/ Give me a *break*.
>
> Unless youre referring to the fact that there's a higher density of
> measurements in urban areas (for example, could be 1 per square mile in
> the city but only 1 per 40 square miles in the country).  Rest assured
> that is *not* a major challenge for anybody who actually understands how
> to do modelling, because you *never* get a nice perfect rectangular mesh
> of perfect sensor readings. You get messy data, broken sensors, that
> one area you couldn't put sensors into the experiment because there was
> a structural support there, the subject sneezed and moved slightly,
> etc etc etc.  So dealing with missing/incomplete data has been understood
> for as long as scientists have been analyzing datasets.

I think he was referring to the idea that previously rural senors are becoming 
urban without necessarily taking that into account when you look at the data.

For instance, say you have 30 weather stations along the stretch of 81 between 
Blacksburg and Roanoke that were put in place in the 1950s and have been 
continually monitored.  As Roanoke and the Blacksburg/Christiansburg Greater 
Metropolitan Area of Traffic Growth have expanded towards each other, the heat-
island effect would have expanded with it.  So assume 10 of the 30 sensors have 
shown continuous temperature increases since 1950.  How much of that is due to 
global warming, and how much of that is due to urban expansion? 

A climatologist at VT would take that into account in their localized studies.  
Somebody at NOAA, viewing raw numbers in a text file, has no way to control for 
that.  It's not that cities are hotter, is that the hot areas around cities 
expand with the cities, and national or international datasets cannot account 
for it.  

If just 5% of your weather data points from 1960 were rural but in 2009 are 
urban or suburban, how much does that skew the entire set?

Wes

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