"Some of the measurement errors in the surface network include -

1) The good old urban heat island (not just related to population growth, but also to traffic and brick & concrete growth)
2) Doug Hoyt's `shrinking skyline' effect (ie. trees, buildings, bushes etc. growing up near and around the box)
3) Screen boxes which are allowed to become dirty and louvres clogged (this happens a lot at the remoter stations)
4) Poor maintenance of the instruments, especially in poorer countries
5) Poor recording by indifferent personnel (eg. on ships, remote locations)
6) Changes during the early 20th century from fixed time recordings to max-min recording
7) Data falsification (eg. data falsification was a way of life by every official in the old USSR)
8) Missing chunks of data (this is very bad in Russia since 1991)
9) Changes in site locations, instruments, and personnel
10) Social & political upheavals (often shows up in the records either as breaks or as obviously anomalous data)
11) The change from manual reading to automatic reading (no longer necessary to open the box - ergo, warming)
12) The warming/cooling effect of slipstream and salt deposits on ship instruments causing erratic data.

There's a tidy little `dirty dozen' to think about. Taken together, one would be quite justified in disregarding the surface network so far as climate determination is concerned. Of course I have not mentioned the added problems of geographic spread, the northern hemisphere bias etc., just the station temperatures themselves. Most of the errors listed above result in `warming creep' in the measured temperature, such as in 1, 2, 3, 6, 7, and 11. The remainder can result in either warming or cooling errors. In other words, taken in total, the combined effect of all these would be to impose a warming creep on any large-scale average such as the hemispheric or global temperature estimates."
http://www.john-daly.com/graytemp/surf-msu.htm#daly2

Was was looking for some detailed information regarding idea of latent heat in the oceans, but ran across this and thought it was interesting. I didn't read the whole section, but there was some other interesting aspects that I invite you to look at.

I saw part of show last last on CSPAN, there was 3 speaker- two who could be described as people who thought global warming was a real threat and one who had a lot doubts about how significant the threat was. I have no doubt that some people on this board might characterize them differently- thinking they were all generally not alarmist enough and too "conservative" in their assessment and one them who was a complete kook. The first speaker was from NASA. And one of the two I would describe as thinking that GW was a threat. To summarize, he didn't show the hockey stick graph, and said that over last century there was a 1 F increase in global temperature and that global temperature could rise significantly in the future. His main solution was largely focused on reducing Methane emissions- he thought this was practical and significant way of affecting GW. He was also under the impression that the Heat Island affect was not affecting affecting his assessment of Global warming [and talked at length about how this couldn't affect his assessment- even seeming a bit dismissive of any claims about this affecting estimates of Global warming. The second guy was James Woolsey, a democrat and mostly politican. He seem to think that CO2 was a big problem, and that oil dependency was an even bigger problem but he thought it could be easily solved if the govt do things to promote what he thought would solve the problem, these were ethanol from not corn, corn, corn, but ethanol from waste products. And hybrids which included using grid electricity to augment the hybrids total power use. He was also a big fan of liquidified coal and with all his ideas, which thought were easily accomplishable- unlike Bush's plan to use Hydrogen technology- could get the equilvent of 500 mph per gallon automoble consumption (gallon of petroleum based fuel, I guess) and wouldn't that scare the Saudis.

The third guy didn't think oil dependency was a unmanagable problem, wasn't overly impressed with Hybrids, and thought that GW might be a problem but was particular impressed with computer modeling which he saw as a science tool used by some to distort facts and was against the general misuse of science by GW advocates. He spend most of his time focusing dangers of pseudo science and wasn't impressed with govt programs with distorted the true cost of such things as hybrid cars. In other words he probably wasn't a democrat.

Anyways the NASA guy put a lot of emphasis the latent heat in the oceans. And many other people are claiming this is the newest "smoking gun" [that vindicates their years of "struggle":].