Yes. The carbon market was based on the SO2 market model, and the difference is unfortunately very great because the SO2 market in the United States, which worked relatively well, is linked to a pollutant that is subject to the same regulation in the same area. Establishing an international carbon market currently represents a difficulty with regard to the setting of ceilings for each industry, which is possible, but which also represents all the recognition of credits that will have to be put on the market to ensure they are unique and that they are additional and so on.
An international standard has been established on this: ISO 14064-2 and 14064-3. In Europe, a carbon market is currently operational, in which each of the industrial sites concerned has received a limit. It's working there.