The science of domino effects regarding climate is not set in stone or even fully understood. It could be really bad, or it may not be as bad as some suspect. I don't really see the utility in assuming the worst of something that could be fixable, or at least mitigated.
Personally, I'm going to look at the proposition of complete and utter doom with a healthy dose of skepticism, and continue to try to make things better where possible.
Out of curiosity, why do you consciously choose to discourage others from trying to make things better? I guess if I thought we were all doomed, there wouldn't be much point in telling others that we're doomed, since it'd be irrelevant anyway. I'd just do my own thing and attempt to live my life to the fullest ability that I have.