If people collectively opt to take some risk, then ethically that's fine. Your car and CO2 emission examples both include reciprocation: everyone benefits and takes risk more or less equally. The problem comes when you participate in putting others at risk when they don't want to reciprocate.

For example, what if 90% of people on a flight would prefer for the 10% of unvaccinated-by-choice people not to be present on the flight at all? They would presumably be fine if the airline put on special "unvaccinated" flights for unvaccinated-by-choice people - except that probably wouldn't be viable as a business model. Since there isn't reciprocation, why should the vaccinated people be forced to be put at risk by you?

What if, instead of flights, we were talking about access to your local grocery store?

No, that's just tyranny of the majority. Just because you've decided to assume CO2 risk doesn't mean I have to consider it ethical (being carbon neutral). It's obviously ethically untenable that just because you guys have decided human extinction is okay, I have to accept that.

> Sure, but if you get in a car you put other people at risk.

Last I checked, car wrecks aren't self-replicating, mutating, exponential-growth deadly diseases.

And so? HIV/AIDS is a self-replicating, mutating, exponential-growth deadly disease and there is a non-zero probability that you carry the virus right now. But I'm not going to ask you to stop having sex.

It still boils down to total risk vs threshold. After all, breathing exposes us to atmospheric-CO2-driven climate change risk which has a small probability of being an extinction-level event.

You can't give AIDs to people by being in the same room with them.

Stop trying to reason using bad analogies. You keep coming to bad conclusions.

Ah, but it's not an analogy. Each time I comment I narrow the scope of your opposition. That is progress. Already you have shrunk it significantly, with each comment yielding more modifiers that diminish the space you cover. With sufficient effort, I could constrain it to the size of a pea, and then we will both be faced with the fact that situations that applying so many restrictive modifiers is akin to adding epicycles. Then it will be obvious that my original statement is correct: it is about aggregate risk.

But perhaps that is best left as an exercise for the reader.