In terms of the uncertainities that you've expressed:
> We don't know how much is exactly anthromorphic and how much is exogenous.
It's a fairly simple mechanism at earth scale - the nature of the insulating blanket in the near vicinity of land and ocean surfaces has changed as a direct result of human activity.
There are increasing levels of CO2 that lead to an increase of trapped energy over and above a long term stasis balance of sunlight in | heat radiated out.
> I believe in science, just hear me out.
That makes two of us at least and the evidence we have is solid, we have libraries of atmospheric air samples that show the changes, we have a wealth of mining and extraction records that log the amount of formerly buried hydrocarbons we've pulled up in the past century, we have instruments that measure the released gases from the ground and show the spectral sinatures from space.
> But even if it were true,
It is true, and the records are public.
> . . . how fucked up is it to tell a child their life is hopelessly doomed when there is nothing they can do?
Who said there is nothing to be done and we're doomed though?
There are changes to be made and habits to be changed.