[dpierce9]

Without agreeing with the paper’s general point, imagine a coal plant that emits particles which cause asthma within a 25 mile radius of the plant that also buys legit offsets for all the carbon they emit. They aren’t buying offsets for the local harms.

[bombcar]

Something else has to be added, or you could just have coal plants perpetually moving around and buying credits by shutting down the previous one.

Now if they offset by buying scrubbers that cleaned similar particulates elsewhere in the world you'd have a "average stayed the same" but the problem moved.