> any action is clearly going to beat sticking ones head in the sand
Not if the action makes things worse than they would have been if you'd done nothing. And given our very poor understanding of how the climate and ecosystems work, any action we take that is not an obvious benefit (like "bring more people out of poverty" or "make our infrastructure more robust", both of which are things we certainly should be doing) is much more likely to make things worse than to make things better.