Unless they've been stored properly, 9-track tapes degrade over time and it becomes nearly impossible to read the data. I've been through this, trying to retrieve data from 20 year old 9-tracks and finding that as I FSF'd into the volume, the tape was stuck together and I could only read the very beginning of the tape.
Tape sticking is a common malady in old audio recording reel tapes also. There are ways to restore these completely blocked up and unplayable tapes.
While I’ve been out, I’m glad that you and several others have pointed out the difficulties with retrieving data from ‘archives’. The problem is huge, and we’ve only touched on parts of it in this thread, but ...
I am NOT ever going to absolve HADCRUt from their resposibility to maintain records of this extremely important original/ hisorical data, AND COMPLETE REASONING how and why they massaged it to create the “value-added records” that they have been presenting to the world. I don’t believe that we will ever be able to recover the data or the reasoning/programming that resulted in the “temperature records” that they have presented, or the reasoning that has resulted in each successive iteration of their “history of temperatures” showing a greater temperature trend due to the way that the data was manipulated.