Since they admit they destroyed (most of) the original data then there is no longer any doubt that they cannot scientifically prove their case.
This means any conclusions or changes in world policy can not be made, until a new study is done. One done in the ‘light of day’.
And since I’m dreaming, a spotless 69 Corvette should appear in my driveway. With a full tank of gas.
The observations, temperature measurements, are evidence. Ideally, any “adjustments” would be reversible, or like I said, benign, like a units conversion. They might also have done something like account for known problems with certain sensors, removing known biases, for instance.
A great number of valid scientific observations are only available second hand. For instance, Ptolemy recorded Hipparchus data, although how Hipparchus arrived at his results is not known and our knowledge of Ptolemy is indirect, from Arab sources, although in the original Greek, which Arab scholars were careful to preserve, though not without accumulating scribal errors over the centuries.
Of course, if Arab scholars could preserve the original Greek of Ptolemy for millenniua, in copied and restored hand written manuscripts, it seems odd that East Angelica University couldn't preserve the world's temperature record for even one generation.