Here is what we know. If you sit inside your house at night time, its going to be warmer inside than outside.
Thinking about this on a larger scale, one would assume that if you develop large cities with lots of dwellings and buildings that it would create more heat.
This is what is called an urban heat island, or UHI. For years, even now, the worlds top climatologists believe that the effect of UHI is minimal.
Here is Laverton, Victoria in the 1940s.
Looks to me like there isnt much warmth from artificial sources in that shot.
In 1940, only 1.1 million people. With little heating from cars, buildings, barely any bitumen, no air cons, computers or televisions, minimal industry as well.
And now? Melbourne has almost 4.5 Million people, but if this is not alarming enough, think about the amount of infrastructure that has developed in the last 70 years. Concrete, concrete, and more concrete. Bitumen roads store heat after reaching 70 degrees during the day, air conditioners release massive heat through summer in Metropolis areas.
In 2012, industry stops for no one, transport industry thrives at all times of the day. And at night time is when the temperatures are affected the most. To demonstrate this clearly, go outside at 2 am and you will see it for yourself. At 2pm the difference would be almost not noticeable.
Lets see how today looks in Laverton, Victoria..
Quite a difference, and was hard to compare because of so little photos from 70 years ago. But you see the point, metropolitan areas store massive heat from the day and create a false warming. The only thing about the Laverton automatic weather station that is acceptable is the fact that it sits in a paddock away from blockages.
What is clearly unacceptable is that this site is still listed as rural, and something the BOM or anyone else seems remotely interested in addressing. This station is in no way rural, and needs to be recognized as urban. This is however no surprise given the track record of temperatures and the BOM.
This also goes hand in hand with the BOMs ACORN data set, which is just as big a load of garbage as the HQ dataset it replaced.
Of course, the BOM refuse to release details of the method of adjustement. It states that the impact is minimal on the overall temperature set as there were just as many negatives as postive adjustments.
Irrelevant, if the record is so good why not produce the codes for the adjustments?
And, does anyone think that UHI has no effect on temperatures?
There is a lot more to come on this subject, and the ACORN dataset also.