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Comment by jah242 | Hacker News Reader

> Secondly, the tropical hole wouldn’t have qualified as a hole under the old definition of a hole, which was defined as having ozone levels below a certain threshold. Lu’s study redefines a hole as an area with ozone loss greater than 25%.

Unless I'm missing something isn't this 'we discovered a new hole because we redefined what a hole is'.... I think I could make a lot of important discoveries if I was allowed to do this.

Still interesting though.

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Well in this case I think it's important to rescale to a relative measure instead of an absolute one. If the ozone continues to strengthen in general, an absolute measure could fail to find a significant hole as it has here.

This isn't an example of moving the goalposts but improving the definition.

Right I would personally like to know if it is dangerous and should be avoided or things i can do while under it to mitigate the effects

Yeah but isn't the absolute measure the one that matters? Because the ozone is blocking UV radiation, and it's the absolute amount of ozone that determines how much radiation is blocked, not the relative amount of ozone in one area vs another.

At best, the relative measure might act as an early warning of a problem. But it could also just be turbulence in a chaotic system. So it's harder to decide if it matters or not.

Exactly! I am not a climate physicist so please someone correct me if I am wrong. But my understanding is the ozone breaks down when it absorbs up light so we should expect it to be thinner in the equatorial regions where there is the most uv right? So the question should not be why the equatorial region is lower then other parts but whether the percentage has gone up or down in that region in recent years.

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