If they showed data for a period where it was unreliable then I'm sure it would be hedged around with strong caveats and error bars. As you assume it is for re

If they showed data for a period where it was unreliable then I'm sure it would be hedged around with strong caveats and error bars. As you assume it is for reliable for the period, perhaps it's good data. It does seem to be within the last century (earliest 1940s from what I can see) where decent scientific measurements would be valid and direct, rather than from centuries past where it would be necessarily indirect and inferred.