I don't want this to sound dismissive, but aren't we all "doomed" in the end anyway? How long does anything we do have an impact anyway? A generation? Two? Five? How many individual people have had an impact on the world five or more generations after they've died, as a percentage of the total population?
Were all those other people's lives meaningless?
I think you're grappling with a fundamental aspect of being mortal, not just one related to the climate.
The hardest part for me to accept is that there are so many people who just don't care. Not about the disasters, the climate refugees, the death toll, the extinction of thousands of species, respiratory diseases, etc.
How can people just accept all that as a fact of life when it's all man-made horrors?
I'm not sure that you're being fair to (many) people.
There are many people to whom this is all doomerism. The world is ending because of ozone depletion. The world is ending because of the oil shortage. The world is ending because of nuclear war. The world is ending because of resource depletion. The world is ending because of topsoil depletion. The world is ending because of aquafer depletion. And now, the world is ending because of climate change. (Yes, climate change figures in several of the other issues...)
People hear all this. And they look around and they see not much actually changing. It's not that they don't care about millions of deaths; they don't believe that the millions of deaths are coming. They think that, yeah, the climate's going to change a bit, and it's going to disrupt things a bit, just like oil got kind of scarce for a while and gasoline got expensive, and that was painful, but we got through it.
It's not that they don't care. It's that they don't believe (and therefore don't care about an outcome that they don't believe in). For many people, slow motion decades-in-the-making doom is not something that feels real, even when it starts to happen.
I don't think we humans were made to think like that. Almost everyone mostly wants to live their lives and has just enough mental energy to care about problems in front of them.
To add to that, for the huge numbers of people who wouldn't be able to ride out a $1,000 emergency without going into debt, who feel like they're not even the primary causal agents in their own lives, the prospect of being able to have any sort of impact on the whole planet is absurd, even if they do have the bandwidth to think about it. They don't have an experience of, "When I decide something should be different, I have the ability to do anything that could actually bring that difference about."
Not the previous poster but it could feel meaningless if you really sincerely think civilization is doomed. At least with optimism for the future you can feel like you mattered to the people close to you, or you were a good cog in a great machine, or you lived a happy life and so will your successors.
Even with daily life, if you think your own life is going to worsen in the future no matter what you do, won't that demotivate you today?
But your own life is going to worsen in the future. To whatever extent you continue to have a future (stay alive), your mind and body will deteriorate. Your relationships will slowly end as the other people die. If you're lucky, you'll build some new ones, but that doesn't reduce the grief of the lost ones.
You might be able to make it happen very slightly slower by making lifestyle changes of varying degrees. But you can make lifestyle changes that will have similar impact on your experience of a warmer world too, if your own life is your concern.
So if you're concerned about everybody's experience, your influence is negligible no matter what. And if you're concerned about your own experience, your influence is slight but diminishing no matter what.
This is still a mortality issue, not a climate change issue.
There is no such thing as "doomed". Humanity is not going to disappear. We can either do better or worse, and there really is no limit to the "worse" side.
Maybe I'm optimistic (for a certain value of optimistic) but I feel we would do mass geoengineering and/or start serious international emission control, enforced by war if necessary, before we get to that.
My very pessimistic view is that things will get very bad first. Which means that humanity will have to deal with mass refugee movements, wars, natural disasters from climate change, and trying to mitigate the effects.
One of those by itself would be difficult to deal with, but all at once would be impossible. In my opinion.
My optimist is that it when it gets real bad governments will do something before it gets catastrophic. Who knows, not a climate scientist, maybe it will be too late.
Were all those other people's lives meaningless?
I think you're grappling with a fundamental aspect of being mortal, not just one related to the climate.