Maybe even if the individual responses are futile in their direct effect, they can still help build a sense of commitment to the eventual solution.

Say a person gives up eating meat. That itself might not fix the problem, even when summed across all the people who make that choice, but the act of sacrificing something in their life helps to establish their identity as someone willing to put forward effort.

IMO the right solution is centrally-imposed taxes on carbon extraction, subsidies on sequestration, and modulation of those financial incentives to whatever numbers necessary to actively manage atmospheric greenhouse gas levels.

I think that individual solutions are a waste of time and can even be dangerous because they can create a sense of complacency. But I think psychologically, they could possibly be part of the path toward people doing all the hard work to get that system of taxes and subsidies in place.

Kinda like how punching a bag can get you trained up to punch out an opponent. Giving up meat becomes an exercise, rather than the work itself.