What we don't have is a 'control planet earth'
We don't need one, that's a bit too trite.
We saw high UV levels arriving in Antarctica.
We could have said we didn't know if it could be bad - we don't have a control planet earth.
We saw the ozone hole - oh that's interesting.
20 miles up, probably doesn't matter.
Some chap said it would let UV through - so it does.
UV is known to kill things. Hmm, don't need another planet to tell that.
What would cause that then?
Dunno
Oh, ozone absorbs UV.
What would destroy ozone?
Well there's chlorine - it acts as a catalyst to break down ozone into oxygen, leaving the chlorine.
What could be causing chlorine in the upper atmoshere?
Is there anything man-made.
Oh yeah, CFC's.
DIYNOT plumbers say:-
But they're heavier than air.
They're produced oop north
So it can't be that
stands to reason.
All bollox anyway
Can't prove it's chlorine
Clever plumber , says chlorine wouldn't settle at the bottom of the world even if it is heavy
It would be everywhere.
So you think it's going to select Antarctica and hide?
You're stupid.
Scientists work out why Antarctica could make sense.
Stable atmosphere
cold for longer than anywhere else
Ask diynot plumber about the dissociaton energy of chlorine ions w.r.t. temperature.
Wot?
Never mind, run along.
What about global warmng potential, if, you know, it turns out to matter?
CO2 is 1
methane is 50
CFCs are around 5000-10000
So we banned CFCs in the 80's,
and the ozone hole mended.
and now we can work out it would have caused a 2.5° extra rise by 2100.
No, you don't need another planet.
Does it matter?
Not really.
We'll stuff the planet sooner or later and there will be nobody to care.