What's your point? Here's mine: We don't know for certain how big an effect we actually have. We don't know whether we are actually responsible for these even

What's your point? Here's mine: We don't know for certain how big an effect we actually have. We don't know whether we are actually responsible for these events (e.g. mass extinction, climate change). But what we do know is that trying to prevent or reverse these things would definitely harm real people, right now, while making certain groups more wealthy and powerful, and keeping certain other groups poor and weak. Therefore, we should not do what we know will certainly cause harm, unless and until we know that not doing it will certainly cause greater harm.