> Topsoil should properly be measured in volume, not distance

Should it though?

And regardless of how clear or unclear that is, I gotta say I dislike seeing when the sum of a multitude of reports is expressed in a headline, only for people to nitpick through it without even attempting to check the actual methodology for themselves.

1 cm/year is 33 times faster than 3 cm/100 years, not a few hundred times faster.

AFAIK terra preta is far from fully understood, and farther still from being widely used. Very cool stuff though.