Over the years there have been numerous technical disagreements between sceptics and the climate faithful. These disputes tend to obscure how close the two sides are scientifically and how far apart politically, but that’s another issue. One major dispute relates to surface temperature data and the way it is altered by official bodies. Adjusted is the official word so I'll stick with altered.
Firstly it is worth noting that raw temperature data is certainly altered. What the public sees is not temperature data, but numbers derived from temperatures and complex alteration protocols.
It is also worth pointing out that there is no such thing as global temperature. Even the mean of two temperatures is not a temperature but a statistic. William Briggs has a good post on what is or is not data.
Secondly, the issue is exceedingly complex, involving vast amounts of data and numerous arguments as to whether or not the data should be altered to gloss over known issues such as TOB, station moves and UHI. There are many examples and the data altered can be a century old. It's a strange game this climate game.
Roy Spencer has a good example of old data being altered to show a warming trend where previously there was no trend. Jo Nova has another and Paul Homewood another.
There are always explanations, but to my mind altering data in this way adds to the uncertainties and clarifies nothing. We didn’t do it in my field. Imagine taking the temperature of a river then altering it to what you think it ought to be. Yet in all this tinkering with climate numbers I see a footling bureaucratic culture rather than nefarious intent.
To my mind, altering data in order to mislead people is not something even a climate scientist would do. That even is not sarcasm by the way – the political pressure must be intensely pervasive and that is something we should not forget. Footling but not corrupt is what it feels like to me. Maybe I'm naive.
Perhaps it won’t make too much difference in the long run, but when fractions of a degree are used to promote a powerful but ailing agenda...