Climate skeptics are at risk of falling into the same exaggeration-trap as do alarmists.
I have written about the exaggeration of past warming by questionable manual adjustments to temperature records for almost a decade. So I don't need to be convinced that these adjustments 1) need to be cleaned up and 2) likely exaggerate past warming.
However, this talk of the "Greatest Scientific Fraud of All Time" is just crazy. If you are interested, I urge you read my piece from the other day for a more balanced view. Don't stop reading without checking out #4.
These recent articles are making it sound like alarmist scientists are simply adding adjustments to past temperatures for no reason. But there are many perfectly valid reasons surface temperature measurements have to be manually adjusted. It is a required part of the process. Just as the satellite data must be adjusted as well, though for different things.
So we should not be suspicious of adjustments per se. We should be concerned about them, though, for a number of reasons:
- In many parts of the world, like in the US, the manual adjustments equal or exceed the measured warming trend. That means the"signal" we are measuring comes entirely from the adjustments. That is, to put it lightly, not ideal.
- The adjustments are extremely poorly documented and impossible for any third party to replicate (one reason the satellite record may be more trustworthy is all the adjustment code for the satellites is open source).
- The adjustments may have a bias. After all, most of the people doing the adjustments expect to see a warming trend historically, and so consider lack of such a trend to be an indicator the data is wrong and in need of adjustment. This is not a conspiracy, but a normal human failing and the reason why the ability to replicate such work is important.
- The adjustments do seem to be very aggressive in identifying any effects that might have artificially created a cooling trend but lax in finding and correcting effects that might have artificially created a warming trend. First and foremost, the changing urban heat island effect in growing cities seems to be under-corrected (Again there is debate on this -- the proprietors of the model believe they have fixed this with a geographic normalizing, correcting biases from nearby thermometers. I and others believe all they are doing is mathematically smearing the error over a larger geography).
Again, I discussed all the pros and cons here. If pushed to the wall, I would say perhaps half of the past warming in the surface temperature record is due to undercorrection of warming biases or overcorrection of cooling biases.