Good catch. I doubt it's even a rounding error right now, but with the space market undergoing a rather rapid growth (good thing!), it's a good time to start tracking this and hopefully address before it turns into a problem.

During the peak something like a million metric tons of refrigerants were making their way into the atmosphere yearly.

Maybe one or two tons of vaguely related chemicals are making their way into the atmosphere in the form of deorbited satellite materials and there's no 1:1 guarantee they're having anything like similar effects.

So it's a number measured in parts per million of the problem we were having in the 80s.

Why do you consider the ideal point for this question absolute 0 zero reentries rather than the minimal number of reentries that don’t cause damage to the atmosphere?

SpaceX wants their Starlink constellation to crack 100,000, and there are plenty of competitors lining up who will surely want to have "the biggest and the best" at some point. None of those sats stay up terribly long, so you'll have a constant cadence of launches and reentries, both of which are a risk for their impact on the climate system, atmosphere, etc.

A largely unstudied risk, and once which will almost certainly be strenuously ignored for as long as possible.

I presume dead orbiting satellites will become a source of valuable refined materials in orbit in not a particularly long time.

It's space junk and then it enters the atmosphere and burns up, I don't think it's too hard to figure out.

Science give us knowledge rooted in hard evidence, science give us models that can be reused as is or used to refine other models. The article mentions how hard it is to monitor atmosphere at 60-80km because it is too high for weather balloons and too low for satellites, now they are doing something about it.

Money spent on science is not a waste of money, even if science come with a negative answer. If you want to find ways to slash wasteful spending, I'd urge you to look at wars: these are really eat a lot of money and give nothing back.

This kind of thinking is exactly what led to the ozone hole in the first place. Let's actually investigate our assumptions this time.

Exactly.. If I have only few hundreds car in the world, will that lead to air pollution ?