For e.g NOx with a high half-life, you are probably right that we are still increasing pollution. For short half-life pollutants like SO2 and CO, I would expect this means the actual atmospheric levels are decreasing.

> For e.g NOx with a high half-life

Their half-life is shorter than a day. On the same magnitude of SO2.

The one of CO is indeed much smaller.

> will actually _decrease_ going forward.

The ratio of (pollution/living person) will decrease. Unless you want to start unaliving people then this is a fixed fact of the world we live on.

Is there a reason to care about that number?

Oh I thought of another one, if people smoke more cigarettes then the ratio of cancer deaths to packs smoked decreases!

You mean “emission of pollutants”. The concentration of CO2 in the atmosphere for example will continue to increase at a slightly lower speed.

...where "pollution" means "air pollution".

I thought greenhouse gasses will increase in concentration as the feedback loop of polar region is forcing trapped gasses out of the ground.

I thinks that’s been predicted but not observed thus far.

On the other hand, once it is observed it will be too late to reverse.

We have on a small scale. Methane is escaping as the permafrost thaws. Boreal forests are also burning down as their climate warms. Reduction in polar ice changes the albedo of the earth to reflect less heat.

At a certain point sufficient warming could trigger a cascade. So far we haven't done that, but it's incorrect to say there's been no release of stored CO2.

Earthworms are moving north and accelerate the breakdown of organic matter in arctic regions too.

Importantly, this article is not primarily about greenhouse gasses.

The idea of having passed peak pollution could suggest that we are beginning to see positive changes...

Agree, but it’s like hurling toward a brick wall at 100mph instead of previously 110mph and saying “we’ve reached peak risk”. Sounds a lot better than “we’re braking but currently we are still going to hit the wall and life expectancy of passengers still currently is measured in second”, but what we need is to push people to brake more, not sugar coat the situation.

So a more accurate statement would be that a derivative of pollution has peaked.

Isn't the concept of pollution highly subjective?

Within certain bounds. Climate scientists likely don't agree on the ideal CO2 PPM level, while agreeing that the current level is not it.

Anyone who wishes to claim pollution is always a subjective concept is welcome to drink a few gallons of water from Lake Karachay.

> Lake Karachay

From https://en.wikipedia.org/wiki/Lake_Karachay

> Today the lake is completely infilled, acting as "a near-surface permanent and dry nuclear waste storage facility."

Doesn’t really matter here, I’m talking about the pollution the article is referring to. I am simply discussing the concept of reaching a peak in pollution vs. a peak in emission of the same pollutants.

Putting the above aside though, I would disagree. Everything is subjective except math (and even there, I think there’s a debate), but I would definitely not classify pollution as _highly_ subjective, that makes it sound it belongs to the category of things that particularly lack consensus, which is definitely not the case amongst the scientific community. Not to say there’s 100% agreement on all things, but I think there’s a broad consensus.

It's really not, for most things. What exactly would you call an oil spill or leaded gas fumes if not pollution?

Certain substances are certainly clear cut.

But consider, I dunno, salt? A little built of salt in the environment is normal. But a whole lot of it is pollution.

I’m no climate scientist but I would think it’s similar to toxicity/poisoning. You can die from water intoxication but certainly you need it to live as well. So no, I don’t think it’s subjective. It seems to me that if something is capable of causing harm in a certain amount, it’s poisonous/pollution/toxic.

Yes, the dangers of Dihydrogen monoxide are well known yet underestimated

Dihydrogen monoxide levels have also peaked.

That's more a quibble over dosage, though, than any subjective disagreement on "can too much salt be a pollutant?"

I think that it is primarily grounded in objective measurements and scientific understanding

Sure, but interpretation of measurements is a largely individual endeavor, one way or another.

And comparison of different, potentially codependent variables, is notably relevant.