I wouldn't say that buying stock in companies that provide air conditioners to consumers fits any definition of fixing the problem of man-made climate change. In fact, wouldn't a warmer planet be better for AC businesses?
This of course will not happen on autopilot, so investors must as always keep a close eye on the CEO and vote in shareholder meetings instead of just buying-and-forgetting.
It doesn't solve climate change of course, but it does make a tiny improvement to one aspect of it. Multiply by every company touching the climate, and you can effect real change.
and from a more short term perspective;
slowing the migration of people from warm places to another will reduce the spike of resources required to house those people.