[morsch]

The world's population can't all move to California, so that's not a sustainable option. But yes, improving home insulation is a low hanging fruit.

The overall impact of aviation is actually less than 5%, though it's fast growing and projected to be 5% and more. (And I doubt only a fraction is related to moving people around.) Note that aviation contributes to global warming in excess of its pure CO2 emissions; at very high altitude even water vapour is an issue. Another point of comparison: aviation's overall impact is about 10% of the entire transport sector, the same amount as all water based shipping.

Either way it's a huge amount, there is no such thing as just an integer percentage of overall emissions.

Source: Wikipedia and IPCC, mostly https://www.ipcc.ch/site/assets/uploads/2018/02/ipcc_wg3_ar5...