> and the one most people are least willing to cut down on.

Getting people to eat less meat or meat from less worse emitters or upgrading existing buildings to low emissions for heating does not seem that much easier.

Anyway, you can't fix the problem with a single change.

People are set in their ways, but there's a continuous rollover of generations. Current young adults are much less into cars, air travel and meat. (Older people do make these changes too, but it's slower).