- 2.3tCO2: "Climate safe per capita emissions" – total remaining climate pollution humanity can emit by 2050 and stay below 2ºC of global warming, divided by global population and 40 years (already out of date)
- 0.5tCO2: portion of per capita emissions (20%) allocated to "travel"
- 20lbs of CO2 per gallon of gasoline burned
If you had a new 50mpg Prius, to remain under the per capita travel carbon budget, you could not drive more than 2,800 miles per year. (The average auto mileage is between 10,000 and 12,000 miles per year driven)
If you account for the embodied energy/emissions of the production and transportation of the car, which is around 4 tons of CO2, and divide that over the typical lifetime of the car – say, 10 years – then you can only expect to actually drive the car 600 miles per year. Less than 2 miles per day. You might as well walk!
If you could account for the emissions required to create and maintain the roads and bridges and other infrastructure supporting car travel (gas stations, mechanics, oil refineries), then cars of any kind are not compatible with a world intending to limit carbon emissions as we've promised to do.
Also, it goes without saying that air travel is impossible, if we care about sticking to a carbon budget. The per passenger emissions from flying are about the same as traveling the same distance by car. Short flights are even more polluting than long distance flights.