We probably don't need to do much of anything about air conditioning specifically, we just need to price in the externalities of energy use generally.

But it might make sense to incentivize (whether through positive incentives or negative incentives on traditional AC, or both) use of geothermal heat pumps instead of air-source heat pumps, since the latter is, pretty much by definition, least efficient when most needed—long-term, they are already a net win for the consumer as well as the environment, but the payoff time is long enough and traditional AC culturally-established enough that it doesn't even tend to be considered as an option enough.