Q8 - Most of the ultraviolet radiation

[charleneroche]

Having trouble understanding answer choice D as opposed to E and how it solves the paradox.
problem: how could uv radiation decrease when the stratospheric ozone decresed?

[rinagoldfield]

Hey charleneroche!

Ok, so you’re right that the discrepancy here is:

How come the stratosphere thinned and yet the ultraviolet radiation in North America decreased?

This is a hard question! I can see why you’re unsure about answer choices (D) and (E).

Answer choice (E) is very tempting, since seems to give us the possibility that the stratosphere didn’t really thin over the spots where UV radiation went down. BUT, note that the stimulus very specifically tells us that the stratospheric ozone layer thinned over North America and that UV radiation decreased over North America. It doesn’t matter if the thinning of the stratosphere varies in general, since we know that it did indeed thin over the spots we’re concerned about.

Answer choice (D), on the other hand, resolves the paradox. The thickened ozone pollution could have absorbed the UV radiation that the thinner stratosphere failed to absorb. This helps us understand why the UV radiation went down when the absorbent stratospheric layer went down, too.

Hope that helps.