Right. I wrote that in the context of the linked article.

So don't think of this scheme as a reasonably efficient way of saving CO2 emissions (there are other much more economically efficient ways); at most it's a bonus.

It follows that it doesn't make sense to justify the scheme on the CO2 emissions benefit. I've seen a lot of that on European subreddits.

But with global warming, that should be almost the only goal for an environmental policy.

The nine euro tickets weren't an environmental policy. The environmental effect is a bonus.