Pay the bill

Let's imagine we decide to pay the oxygen we use to those countries who produce it.
How would it work?

First, most of the O2/CO2 balance is "used" by countries with big industrial production which, long time ago, were the first nation to emerge with a fast economy, now it's more the "developing" countries.
This is happening because those countries normally have a lower cost for manpower, in other words because we are taking advantage of them.

This means that at first, this "O2 cost" would hit them, which is not necessarily good, however they are the ones producing the goods, so they will raise prices to cover for the extra cost.
They will need to invest to improve their industrial infrastructure to be more efficient and less pollutant, meaning prices will be even higher.

Finally they might even lose competitive advantage versus other countries, but I believe this could be positive.
Setting the same rules for everybody will push us all to have a comparable standard of life : roughly the same working hours, same life conditions, rights etc.
In the mid-long term, this would be indeed beneficial and would also limit dangerous phenomena such as massive emigration.

I believe emigration is somehow good -I emigrated myself- as it forces cultures to merge, it brings cultural richness.
What is not good is when people must leave their land to survive, generating huge migration flows that can hardly be integrate organically in the destination land.

Turning Amazzonia in a profitable resource because of its trees, is probably the only way to save it.
We even have the technology to reclaim green land from deserts, if we are not doing it now it's just because it's not profitable.
(Clean) Water is another critical resource, by reducing industrial waste, promoting a greener industry we would also save this resource.

How could it work?
We are already monitoring CO2 levels, using satellites , so we already have the data.
It would be enough to establish the price, which I believe should be 0 (zero) when the CO2/O2 balance is perfect and raise progressively as this balance worsens.
We can decide a critical level (dangerous for humans and other animals) and set the price for that level to be equal to oil : number of Kg of O2 needed to burn a barrel of oil will cost the same as a barrel of oil itself.
Intermediate prices would be calculated with a linear progression.

The cost would be paid by consumers: the more you consume, the more you pay.
I think it's fair, those costs exist in real life and they should not be hidden, for the benefit of the whole planet (and not of as small privileged "elite")