When collecting data the instruments used and the method of collection is vital. This is especially true with non-repeatable, representative data.
What do I mean by those terms? Non-repeatable is when you cannot go back and measure it again. Unlike measuring the deflection in a piece of steel or capturing a fish from a given area, temperature data is time sensitive. If you want to know the temperature in Oxnard at 14:54 March 2nd 2004 then you've got one chance to do it.
Oxnard fits into the second point, representative. All instruments only record a small area, relative to the actual medium being tested. It's like having a thermometer in your house, it does not record the temperature of the entire house, just the immediate area where it is located.
Hence the location is vital. Put it close to a radiator and it'll be warmer, in the freezer much colder, and so on. Hence when recording temperatures over a long period the integrity of the recording station is vital.
Since one small instrument is often used to represent the temperature of a vast area a small change in location or ambient conditions can create the illusion of a global change (would you think your house is on fire because your thermometer is reading your oven temp?).
The example is not as ludicrous as it appears since much of the global warming claims depend on variations on less than the order of individual degrees.
Doug Ross shows just where these probes are placed.
Also moving the amount of shade a probe gets will dramatically affect the temperature, as will the kind of probe and even the methods of averaging. The uncertainty analysis of global temperature data must be exceptionably laughable.
And even with the existing data how about comparing "human emissions (the alleged cause) and temperature (the alleged effect)?" Nahhh...
This doesn't even mention the lack of experimental verification or variation, the incredibly small time scale of "valid" data, the attempts of "scientists" to obfuscate their methods and hide raw data, and that coincidentally every solution of global warming involves the same type of big government mass industrial control.